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VI(1P)			   POSIX Programmer's Manual			VI(1P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME
       vi - screen-oriented (visual) display editor

SYNOPSIS
       vi [-rR][-c command][-t tagstring][-w size][file ...]

DESCRIPTION
       This utility shall be provided on systems that both  support  the  User
       Portability Utilities option and define the POSIX2_CHAR_TERM symbol. On
       other systems it is optional.

       The vi (visual) utility is a screen-oriented text editor. Only the open
       and  visual  modes of the editor are described in IEEE Std 1003.1-2001;
       see the line editor ex for additional editing capabilities used in  vi.
       The  user  can  switch  back and forth between vi and ex and execute ex
       commands from within vi.

       This reference page uses the term edit buffer to describe  the  current
       working	text.  No specific implementation is implied by this term. All
       editing changes are performed on the edit buffer, and no changes to  it
       shall affect any file until an editor command writes the file.

       When  using  vi,	 the terminal screen acts as a window into the editing
       buffer. Changes made to the editing buffer shall be  reflected  in  the
       screen display; the position of the cursor on the screen shall indicate
       the position within the editing buffer.

       Certain terminals do not have all the capabilities necessary to support
       the  complete vi definition. When these commands cannot be supported on
       such terminals, this condition shall not produce an error message  such
       as "not an editor command" or report a syntax error. The implementation
       may either accept the commands and produce results on the  screen  that
       are  the	 result of an unsuccessful attempt to meet the requirements of
       this volume of IEEE Std 1003.1-2001 or report an error  describing  the
       terminal-related deficiency.

OPTIONS
       The  vi	utility	 shall	conform	 to  the  Base	Definitions  volume of
       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -c  command
	      See the ex command description of the -c option.

       -r     See the ex command description of the -r option.

       -R     See the ex command description of the -R option.

       -t  tagstring
	      See the ex command description of the -t option.

       -w  size
	      See the ex command description of the -w option.

OPERANDS
       See the OPERANDS section of the ex command for a description of the op‐
       erands supported by the vi command.

STDIN
       If  standard input is not a terminal device, the results are undefined.
       The standard input consists of a series of commands and input text,  as
       described in the EXTENDED DESCRIPTION section.

       If  a  read  from the standard input returns an error, or if the editor
       detects an end-of-file condition from the standard input, it  shall  be
       equivalent to a SIGHUP asynchronous event.

INPUT FILES
       See  the INPUT FILES section of the ex command for a description of the
       input files supported by the vi command.

ENVIRONMENT VARIABLES
       See the ENVIRONMENT VARIABLES section of the ex command for  the	 envi‐
       ronment variables that affect the execution of the vi command.

ASYNCHRONOUS EVENTS
       See  the	 ASYNCHRONOUS  EVENTS  section	of the ex for the asynchronous
       events that affect the execution of the vi command.

STDOUT
       If standard output is not a terminal device, undefined results occur.

       Standard output may be used for writing prompts to the user, for infor‐
       mational messages, and for writing lines from the file.

STDERR
       If standard output is not a terminal device, undefined results occur.

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       See the OUTPUT FILES section of the ex command for a description of the
       output files supported by the vi command.

EXTENDED DESCRIPTION
       If the terminal does not have the capabilities necessary to support  an
       unspecified  portion  of the vi definition, implementations shall start
       initially in ex mode or open mode.  Otherwise, after initialization, vi
       shall be in command mode; text input mode can be entered by one of sev‐
       eral commands used to insert or change text. In text input mode,	 <ESC>
       can  be	used  to  return  to  command  mode;  other  uses of <ESC> are
       described later in this section; see Terminate Command or Input Mode .

   Initialization in ex and vi
       See Initialization in ex and vi for a description of ex and vi initial‐
       ization for the vi utility.

   Command Descriptions in vi
       The  following  symbols	are  used  in this reference page to represent
       arguments to commands.

       buffer See the description of buffer in the EXTENDED  DESCRIPTION  sec‐
	      tion of the ex utility; see Command Descriptions in ex .

       In  open	 and visual mode, when a command synopsis shows both [ buffer]
       and [ count] preceding the command  name,  they	can  be	 specified  in
       either order.

       count  A	 positive  integer  used  as an optional argument to most com‐
	      mands, either to give a repeat count or as a size. This argument
	      is optional and shall default to 1 unless otherwise specified.

       The  Synopsis lines for the vi commands <control>-G, <control>-L, <con‐
       trol>-R, <control>-], %, &, ^, D, m, M, Q, u, U, and  ZZ	 do  not  have
       count  as an optional argument. Regardless, it shall not be an error to
       specify a count to these commands, and any  specified  count  shall  be
       ignored.

       motion An  optional  trailing argument used by the !, <, >, c, d, and y
	      commands, which is used to indicate  the	region	of  text  that
	      shall  be	 affected by the command. The motion can be either one
	      of the command characters repeated or one of  several  other  vi
	      commands (listed in the following table). Each of the applicable
	      commands specifies the region of text matched by	repeating  the
	      command; each command that can be used as a motion command spec‐
	      ifies the region of text it affects.

       Commands that take motion arguments operate on either lines or  charac‐
       ters,  depending	 on  the  circumstances.  When operating on lines, all
       lines that fall partially or wholly within the  text  region  specified
       for  the	 command shall be affected. When operating on characters, only
       the exact characters in the specified text region  shall	 be  affected.
       Each motion command specifies this individually.

       When  commands  that may be motion commands are not used as motion com‐
       mands, they shall set the current position to the current line and col‐
       umn as specified.

       The following commands shall be valid cursor motion commands:

	      <apostrophe>	 (    -	   j	H
	      <carriage-return>	 )    $	   k	L
	      <comma>		 [[   %	   l	M
	      <control>-H	 ]]   _	   n	N
	      <control>-N	 {    ;	   t	T
	      <control>-P	 }    ?	   w	W
	      <grave accent>	 ^    b	   B
	      <newline>		 +    e	   E
	      <space>		 |    f	   F
	      <zero>		 /    h	   G

       Any  count that is specified to a command that has an associated motion
       command shall be applied to the motion command. If a count  is  applied
       to both the command and its associated motion command, the effect shall
       be multiplicative.

       The following symbols are used in this section to specify locations  in
       the edit buffer:

       current character

	      The character that is currently indicated by the cursor.

       end of a line

	      The  point  located between the last non- <newline> (if any) and
	      the terminating <newline> of a line. For	an  empty  line,  this
	      location coincides with the beginning of the line.

       end of the edit buffer

	      The  location  corresponding  to the end of the last line in the
	      edit buffer.

       The following symbols are used  in  this	 section  to  specify  command
       actions:

       bigword
	      In the POSIX locale, vi shall recognize four kinds of bigwords:

	       1. A maximal sequence of non- <blank>s preceded and followed by
		  <blank>s or the beginning or end of a line or the edit  buf‐
		  fer

	       2. One or more sequential blank lines

	       3. The first character in the edit buffer

	       4. The last non- <newline> in the edit buffer

       word   In the POSIX locale, vi shall recognize five kinds of words:

	       1. A  maximal  sequence	of  letters,  digits, and underscores,
		  delimited at both ends by:

		   * Characters other than letters, digits, or underscores

		   * The beginning or end of a line

		   * The beginning or end of the edit buffer

	       2. A maximal sequence of characters other than letters, digits,
		  underscores, or <blank>s, delimited at both ends by:

		   * A letter, digit, underscore

		   * <blank>s

		   * The beginning or end of a line

		   * The beginning or end of the edit buffer

	       3. One or more sequential blank lines

	       4. The first character in the edit buffer

	       5. The last non- <newline> in the edit buffer

       section boundary

	      A section boundary is one of the following:

	       1. A line whose first character is a <form-feed>

	       2. A line whose first character is an open curly brace ( '{' )

	       3. A  line  whose  first character is a period and whose second
		  and third characters match a two-character pair in the  sec‐
		  tions edit option (see ed)

	       4. A  line  whose  first	 character  is a period and whose only
		  other character matches the first character of a two-charac‐
		  ter pair in the sections edit option, where the second char‐
		  acter of the two-character pair is a <space>

	       5. The first line of the edit buffer

	       6. The last line of the edit buffer if the  last	 line  of  the
		  edit	buffer	is empty or if it is a ]] or } command; other‐
		  wise, the last non- <newline> of the last line of  the  edit
		  buffer

       paragraph boundary

	      A paragraph boundary is one of the following:

	       1. A section boundary

	       2. A  line  whose  first character is a period and whose second
		  and third characters match a two-character pair in the para‐
		  graphs edit option (see ed)

	       3. A  line  whose  first	 character  is a period and whose only
		  other character matches the first character of a two-charac‐
		  ter  pair  in	 the  paragraphs edit option, where the second
		  character of the two-character pair is a <space>

	       4. One or more sequential blank lines

       remembered search direction

	      See the description of remembered search direction in ed.

       sentence boundary

	      A sentence boundary is one of the following:

	       1. A paragraph boundary

	       2. The first non- <blank> that occurs after a paragraph	bound‐
		  ary

	       3. The  first  non- <blank> that occurs after a period ( '.' ),
		  exclamation mark ( '!' ), or question mark ( '?' ), followed
		  by  two <space>s or the end of a line; any number of closing
		  parenthesis ( ')' ), closing brackets ( ']' ), double	 quote
		  ( ' ),' or single quote ( '" ) characters can appear between
		  the punctuation mark and the two <space>s or end-of-line

       In the remainder of the description of the vi utility, the term "buffer
       line"  refers  to a line in the edit buffer and the term "display line"
       refers to the line or lines on the display screen used to  display  one
       buffer  line.  The  term	 "current  line"  refers to a specific "buffer
       line".

       If there are display lines on the screen for which there are no	corre‐
       sponding	 buffer	 lines	because they correspond to lines that would be
       after the end of the file, they shall be displayed as a single tilde  (
       '~' ) character, plus the terminating <newline>.

       The  last  line of the screen shall be used to report errors or display
       informational messages. It shall also be used to display the input  for
       "line-oriented  commands"  ( /, ?, :, and !). When a line-oriented com‐
       mand is executed, the editor shall enter text input mode	 on  the  last
       line  on	 the screen, using the respective command characters as prompt
       characters. (In the case of the ! command, the associated motion	 shall
       be  entered  by the user before the editor enters text input mode.) The
       line entered by the user shall be terminated by	a  <newline>,  a  non-
       <control>-V-escaped   <carriage-return>,	 or  unescaped	<ESC>.	It  is
       unspecified if more characters than require a display width  minus  one
       column number of screen columns can be entered.

       If  any	command	 is  executed  that overwrites a portion of the screen
       other than the last line of the screen (for example, the ex suspend  or
       !  commands),  other  than  the	ex  shell  command,  the user shall be
       prompted for a character before the screen is refreshed	and  the  edit
       session continued.

       <tab>s  shall  take  up	the number of columns on the screen set by the
       tabstop edit option (see ed), unless there are less than that number of
       columns before the display margin that will cause the displayed line to
       be folded; in this case, they shall only take up the number of  columns
       up to that boundary.

       The cursor shall be placed on the current line and relative to the cur‐
       rent column as specified by each command	 described  in	the  following
       sections.

       In  open	 mode,	if  the current line is not already displayed, then it
       shall be displayed.

       In visual mode, if the current line is not displayed,  then  the	 lines
       that  are displayed shall be expanded, scrolled, or redrawn to cause an
       unspecified portion of the current line to be displayed.	 If the screen
       is  redrawn,  no more than the number of display lines specified by the
       value of the window edit option shall be displayed (unless the  current
       line  cannot  be	 completely  displayed	in the number of display lines
       specified by the window edit option) and	 the  current  line  shall  be
       positioned  as  close  to the center of the displayed lines as possible
       (within the constraints imposed by the distance of the  line  from  the
       beginning or end of the edit buffer). If the current line is before the
       first line in the display and the screen is  scrolled,  an  unspecified
       portion	of  the	 current line shall be placed on the first line of the
       display. If the current line is after the last line in the display  and
       the  screen  is	scrolled,  an  unspecified portion of the current line
       shall be placed on the last line of the display.

       In visual mode, if a line from the edit buffer (other than the  current
       line) does not entirely fit into the lines at the bottom of the display
       that are available for its presentation, the editor may choose  not  to
       display	any  portion of the line. The lines of the display that do not
       contain text from the edit buffer for this reason shall each consist of
       a single '@' character.

       In  visual  mode,  the editor may choose for unspecified reasons to not
       update lines in the display to correspond to the underlying edit buffer
       text. The lines of the display that do not correctly correspond to text
       from the edit buffer for this reason shall  consist  of	a  single  '@'
       character (plus the terminating <newline>), and the <control>-R command
       shall cause the editor to update the screen to correctly represent  the
       edit buffer.

       Open  and  visual mode commands that set the current column set it to a
       column position in the display, and not a  character  position  in  the
       line.  In  this case, however, the column position in the display shall
       be calculated for an infinite width display; for	 example,  the	column
       related to a character that is part of a line that has been folded onto
       additional screen lines will be offset from  the	 display  line	column
       where  the  buffer  line begins, not from the beginning of a particular
       display line.

       The display cursor column in the display is based on the value  of  the
       current column, as follows, with each rule applied in turn:

	1. If the current column is after the last display line column used by
	   the displayed line, the display cursor column shall be set  to  the
	   last display line column occupied by the last non- <newline> in the
	   current line; otherwise, the display cursor column shall be set  to
	   the current column.

	2. If  the character of which some portion is displayed in the display
	   line column specified by the display cursor	column	requires  more
	   than a single display line column:

	    a. If  in  text  input  mode,  the	display cursor column shall be
	       adjusted to the first display line column in which any  portion
	       of that character is displayed.

	    b. Otherwise,  the	display cursor column shall be adjusted to the
	       last display line column in which any portion of that character
	       is displayed.

       The  current  column  shall  not be changed by these adjustments to the
       display cursor column.

       If an error occurs during the parsing or execution of a vi command:

	* The terminal shall be alerted. Execution of  the  vi	command	 shall
	  stop,	 and  the  cursor  (for	 example, the current line and column)
	  shall not be further modified.

	* Unless otherwise specified by the following command sections, it  is
	  unspecified whether an informational message shall be displayed.

	* Any partially entered vi command shall be discarded.

	* If the vi command resulted from a map expansion, all characters from
	  that map expansion shall be discarded, except as otherwise specified
	  by the map command (see ed).

	* If  the  vi command resulted from the execution of a buffer, no fur‐
	  ther commands caused by the execution of the buffer  shall  be  exe‐
	  cuted.

   Page Backwards
       Synopsis:

	      [count] <control>-B

       If  in  open  mode, the <control>-B command shall behave identically to
       the z command. Otherwise, if the current line is the first line of  the
       edit buffer, it shall be an error.

       If  the	window	edit option is less than 3, display a screen where the
       last line of the display shall be some portion of:

	      (current first line) -1

       otherwise, display a screen where the first line of the	display	 shall
       be some portion of:

	      (current first line) - count x ((window edit option) -2)

       If  this	 calculation  would  result in a line that is before the first
       line of the edit buffer, the first line of the  display	shall  display
       some portion of the first line of the edit buffer.

       Current	line:  If  no  lines  from  the previous display remain on the
       screen, set to the last line of the display; otherwise, set to ( line -
       the number of new lines displayed on this screen).

       Current column: Set to non- <blank>.

   Scroll Forward
       Synopsis:

	      [count] <control>-D

       If the current line is the last line of the edit buffer, it shall be an
       error.

       If no count is specified, count shall default to the  count  associated
       with  the  previous <control>-D or <control>-U command. If there was no
       previous <control>-D or <control>-U command, count shall default to the
       value of the scroll edit option.

       If  in  open mode, write lines starting with the line after the current
       line, until count lines or the last line of the file have been written.

       Current line: If the current line + count is past the last line of  the
       edit buffer, set to the last line of the edit buffer; otherwise, set to
       the current line + count.

       Current column: Set to non- <blank>.

   Scroll Forward by Line
       Synopsis:

	      [count] <control>-E

       Display the line count lines after the last line currently displayed.

       If the last line of the edit buffer is displayed, it shall be an error.
       If  there  is  no  line	count lines after the last line currently dis‐
       played, the last line of the display shall display some portion of  the
       last line of the edit buffer.

       Current line: Unchanged if the previous current character is displayed;
       otherwise, set to the first line displayed.

       Current column: Unchanged.

   Page Forward
       Synopsis:

	      [count] <control>-F

       If in open mode, the <control>-F command shall  behave  identically  to
       the  z  command. Otherwise, if the current line is the last line of the
       edit buffer, it shall be an error.

       If the window edit option is less than 3, display a  screen  where  the
       first line of the display shall be some portion of:

	      (current last line) +1

       otherwise,  display  a screen where the first line of the display shall
       be some portion of:

	      (current first line) + count x ((window edit option) -2)

       If this calculation would result in a line that is after the last  line
       of  the	edit  buffer,  the last line of the display shall display some
       portion of the last line of the edit buffer.

       Current line: If no lines from  the  previous  display  remain  on  the
       screen,	set to the first line of the display; otherwise, set to ( line
       + the number of new lines displayed on this screen).

       Current column: Set to non- <blank>.

   Display Information
       Synopsis:

	      <control>-G

       This command shall be equivalent to the ex file command.

   Move Cursor Backwards
       Synopsis:

	      [count] <control>-H

	      [count] h

	      the current erase character (see stty)

       If there are no characters before the current character on the  current
       line, it shall be an error. If there are less than count previous char‐
       acters on the current line, count shall be adjusted to  the  number  of
       previous characters on the line.

       If used as a motion command:

	1. The	text  region  shall  be from the character before the starting
	   cursor up to and including the countth character before the	start‐
	   ing cursor.

	2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current	column:	 Set  to  ( column - the number of columns occupied by
       count characters ending with the previous current column).

   Move Down
       Synopsis:

	      [count] <newline>

	      [count] <control>-J

	      [count] <control>-M

	      [count] <control>-N

	      [count] j

	      [count] <carriage-return>

	      [count] +

       If there are less than count lines after the current line in  the  edit
       buffer, it shall be an error.

       If used as a motion command:

	1. The	text region shall include the starting line and the next count
	   - 1 lines.

	2. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       Current line: Set to current line+ count.

       Current column: Set to non- <blank> for	the  <carriage-return>,	 <con‐
       trol>-M, and + commands; otherwise, unchanged.

   Clear and Redisplay
       Synopsis:

	      <control>-L

       If in open mode, clear the screen and redisplay the current line.  Oth‐
       erwise, clear and redisplay the screen.

       Current line: Unchanged.

       Current column: Unchanged.

   Move Up
       Synopsis:

	      [count] <control>-P

	      [count] k

	      [count] -

       If there are less than count lines before the current line in the  edit
       buffer, it shall be an error.

       If used as a motion command:

	1. The	text  region  shall include the starting line and the previous
	   count lines.

	2. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       Current line: Set to current line - count.

       Current column: Set to non-  <blank>  for  the  -  command;  otherwise,
       unchanged.

   Redraw Screen
       Synopsis:

	      <control>-R

       If  any	lines have been deleted from the display screen and flagged as
       deleted on the terminal using the @ convention (see  the	 beginning  of
       the  EXTENDED  DESCRIPTION section), they shall be redisplayed to match
       the contents of the edit buffer.

       It is unspecified whether lines flagged with @ because they do not  fit
       on the terminal display shall be affected.

       Current line: Unchanged.

       Current column: Unchanged.

   Scroll Backward
       Synopsis:

	      [count] <control>-U

       If  the	current line is the first line of the edit buffer, it shall be
       an error.

       If no count is specified, count shall default to the  count  associated
       with  the  previous <control>-D or <control>-U command. If there was no
       previous <control>-D or <control>-U command, count shall default to the
       value of the scroll edit option.

       Current line: If count is greater than the current line, set to 1; oth‐
       erwise, set to the current line - count.

       Current column: Set to non- <blank>.

   Scroll Backward by Line
       Synopsis:

	      [count] <control>-Y

       Display the line count lines before the first line currently displayed.

       If the current line is the first line of the edit buffer, it  shall  be
       an error. If this calculation would result in a line that is before the
       first line of the edit buffer, the first line of the display shall dis‐
       play some portion of the first line of the edit buffer.

       Current line: Unchanged if the previous current character is displayed;
       otherwise, set to the first line displayed.

       Current column: Unchanged.

   Edit the Alternate File
       Synopsis:

	      <control>-^

       This command shall be equivalent to  the	 ex  edit  command,  with  the
       alternate pathname as its argument.

   Terminate Command or Input Mode
       Synopsis:

	      <ESC>

       If a partial vi command (as defined by at least one, non- count charac‐
       ter) has been entered, discard the count and the command character(s).

       Otherwise, if no command characters have been entered,  and  the	 <ESC>
       was  the	 result	 of a map expansion, the terminal shall be alerted and
       the <ESC> character shall be discarded, but it shall not be an error.

       Otherwise, it shall be an error.

       Current line: Unchanged.

       Current column: Unchanged.

   Search for tagstring
       Synopsis:

	      <control>-]

       If the current character is not a word  or  <blank>,  it	 shall	be  an
       error.

       This  command shall be equivalent to the ex tag command, with the argu‐
       ment to that command defined as follows.

       If the current character is a <blank>:

	1. Skip all <blank>s after the cursor up to the end of the line.

	2. If the end of the line is reached, it shall be an error.

       Then, the argument to the ex tag command shall be the current character
       and  all	 subsequent  characters, up to the first non-word character or
       the end of the line.

   Move Cursor Forward
       Synopsis:

	      [count] <space>

	      [count] l	 (ell)

       If there are less than count non- <newline>s after the  cursor  on  the
       current	line, count shall be adjusted to the number of non- <newline>s
       after the cursor on the line.

       If used as a motion command:

	1. If the current or countth character after the cursor	 is  the  last
	   non-	 <newline>  in the line, the text region shall be comprised of
	   the current character up to and including the last  non-  <newline>
	   in  the  line. Otherwise, the text region shall be from the current
	   character up to, but not including, the countth character after the
	   cursor.

	2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       If there are no non- <newline>s after the current character on the cur‐
       rent line, it shall be an error.

       Current line: Unchanged.

       Current column: Set to the last column that displays any portion of the
       countth character after the current character.

   Replace Text with Results from Shell Command
       Synopsis:

	      [count] ! motion shell-commands <newline>

       If the motion command is the ! command repeated:

	1. If  the edit buffer is empty and no count was supplied, the command
	   shall be the equivalent of the ex :read ! command,  with  the  text
	   input, and no text shall be copied to any buffer.

	2. Otherwise:

	    a. If there are less than count -1 lines after the current line in
	       the edit buffer, it shall be an error.

	    b. The text region shall be	 from  the  current  line  up  to  and
	       including the next count -1 lines.

       Otherwise, the text region shall be the lines in which any character of
       the text region specified by the motion command appear.

       Any text copied to a buffer shall be in line mode.

       This command shall be equivalent to the ex ! command for the  specified
       lines.

   Move Cursor to End-of-Line
       Synopsis:

	      [count] $

       It shall be an error if there are less than ( count -1) lines after the
       current line in the edit buffer.

       If used as a motion command:

	1. If count is 1:

	    a. It shall be an error if the line is empty.

	    b. Otherwise, the text region shall consist of all characters from
	       the  starting  cursor  to  the last non- <newline> in the line,
	       inclusive, and any text copied to a buffer shall be in  charac‐
	       ter mode.

	2. Otherwise,  if  the	starting  cursor  position is at or before the
	   first non- <blank> in the line, the text region  shall  consist  of
	   the	current	 and  the next count -1 lines, and any text saved to a
	   buffer shall be in line mode.

	3. Otherwise, the text region shall consist of all characters from the
	   starting  cursor  to	 the  last  non- <newline> in the line that is
	   count -1 lines forward from the current line, and any  text	copied
	   to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the current line + count-1.

       Current column: The current column is set to the last display line col‐
       umn of the last non- <newline> in the line, or column position 1 if the
       line is empty.

       The  current  column  shall  be adjusted to be on the last display line
       column of the last non- <newline> of the	 current  line	as  subsequent
       commands	 change	 the current line, until a command changes the current
       column.

   Move to Matching Character
       Synopsis:

	      %

       If the character at the current position is not a parenthesis, bracket,
       or  curly  brace,  search forward in the line to the first one of those
       characters. If no such character is found, it shall be an error.

       The matching character shall be	the  parenthesis,  bracket,  or	 curly
       brace  matching the parenthesis, bracket, or curly brace, respectively,
       that was at the current position or that was found on the current line.

       Matching shall be determined as follows, for an open parenthesis:

	1. Set a counter to 1.

	2. Search forwards until a parenthesis is found or the end of the edit
	   buffer is reached.

	3. If the end of the edit buffer is reached, it shall be an error.

	4. If an open parenthesis is found, increment the counter by 1.

	5. If a close parenthesis is found, decrement the counter by 1.

	6. If the counter is zero, the current character is the matching char‐
	   acter.

       Matching for a close parenthesis shall be equivalent, except  that  the
       search shall be backwards, from the starting character to the beginning
       of the buffer, a close parenthesis shall increment the  counter	by  1,
       and an open parenthesis shall decrement the counter by 1.

       Matching for brackets and curly braces shall be equivalent, except that
       searching shall be done for open and close brackets or open  and	 close
       curly braces. It is implementation-defined whether other characters are
       searched for and matched as well.

       If used as a motion command:

	1. If the matching cursor was after the starting cursor	 in  the  edit
	   buffer, and the starting cursor position was at or before the first
	   non- <blank> non- <newline> in the starting line, and the  matching
	   cursor  position  was  at or after the last non- <blank> non- <new‐
	   line> in the matching line, the text region shall  consist  of  the
	   current  line  to the matching line, inclusive, and any text copied
	   to a buffer shall be in line mode.

	2. If the matching cursor was before the starting cursor in  the  edit
	   buffer,  and	 the starting cursor position was at or after the last
	   non- <blank> non- <newline> in the starting line, and the  matching
	   cursor  position was at or before the first non- <blank> non- <new‐
	   line> in the matching line, the text region shall  consist  of  the
	   current  line  to the matching line, inclusive, and any text copied
	   to a buffer shall be in line mode.

	3. Otherwise, the text region shall consist of the starting  character
	   to the matching character, inclusive, and any text copied to a buf‐
	   fer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the line where the matching character is located.

       Current column: Set to the last column where any portion of the	match‐
       ing character is displayed.

   Repeat Substitution
       Synopsis:

	      &

       Repeat the previous substitution command. This command shall be equiva‐
       lent to the ex & command with the current line as  its  addresses,  and
       without options, count, or flags.

   Return to Previous Context at Beginning of Line
       Synopsis:

	      ' character

       It  shall  be an error if there is no line in the edit buffer marked by
       character.

       If used as a motion command:

	1. If the starting cursor is after the marked cursor, then  the	 loca‐
	   tions of the starting cursor and the marked cursor in the edit buf‐
	   fer shall be logically swapped.

	2. The text region shall consist  of  the  starting  line  up  to  and
	   including the marked line, and any text copied to a buffer shall be
	   in line mode.

       If not used as a motion command:

       Current line: Set to the line referenced by the mark.

       Current column: Set to non- <blank>.

   Return to Previous Context
       Synopsis:

	      ` character

       It shall be an error if the marked line is no longer in the  edit  buf‐
       fer.   If  the  marked line no longer contains a character in the saved
       numbered character position, it shall be as if the marked  position  is
       the first non- <blank>.

       If used as a motion command:

	1. It shall be an error if the marked cursor references the same char‐
	   acter in the edit buffer as the starting cursor.

	2. If the starting cursor is after the marked cursor, then  the	 loca‐
	   tions of the starting cursor and the marked cursor in the edit buf‐
	   fer shall be logically swapped.

	3. If the starting line is empty or  the  starting  cursor  is	at  or
	   before  the first non- <blank> non- <newline> of the starting line,
	   and the marked cursor line is empty or the marked cursor references
	   the	first  character  of  the  marked cursor line, the text region
	   shall consist of all lines containing characters from the  starting
	   cursor  to  the  line before the marked cursor line, inclusive, and
	   any text copied to a buffer shall be in line mode.

	4. Otherwise, if the marked cursor line is empty or the marked	cursor
	   references  a  character  at	 or before the first non- <blank> non-
	   <newline> of the marked cursor line, the region of  text  shall  be
	   from	 the  starting	cursor	to the last non- <newline> of the line
	   before the marked cursor line, inclusive, and any text copied to  a
	   buffer shall be in character mode.

	5. Otherwise,  the  region  of	text shall be from the starting cursor
	   (inclusive), to the marked cursor (exclusive), and any text	copied
	   to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the line referenced by the mark.

       Current	column:	 Set  to  the  last column in which any portion of the
       character referenced by the mark is displayed.

   Return to Previous Section
       Synopsis:

	      [count] [[

       Move the cursor backward through the edit buffer to the first character
       of the previous section boundary, count times.

       If used as a motion command:

	1. If  the  starting cursor was at the first character of the starting
	   line or the starting line was empty, and the first character of the
	   boundary  was  the  first  character of the boundary line, the text
	   region shall consist of the current line up to  and	including  the
	   line where the countth next boundary starts, and any text copied to
	   a buffer shall be in line mode.

	2. If the boundary was the last line of the edit buffer	 or  the  last
	   non- <newline> of the last line of the edit buffer, the text region
	   shall consist of the last character in the edit buffer  up  to  and
	   including  the  starting  character, and any text saved to a buffer
	   shall be in character mode.

	3. Otherwise, the text region shall consist of the starting  character
	   up  to  but	not  including the first character in the countth next
	   boundary, and any text copied to a buffer  shall  be	 in  character
	   mode.

       If not used as a motion command:

       Current	line:  Set  to the line where the countth next boundary in the
       edit buffer starts.

       Current column: Set to the last column in  which	 any  portion  of  the
       first  character	 of  the countth next boundary is displayed, or column
       position 1 if the line is empty.

   Move to Next Section
       Synopsis:

	      [count] ]]

       Move the cursor forward through the edit buffer to the first  character
       of the next section boundary, count times.

       If used as a motion command:

	1. If  the  starting cursor was at the first character of the starting
	   line or the starting line was empty, and the first character of the
	   boundary  was  the  first  character of the boundary line, the text
	   region shall consist of the current line up to  and	including  the
	   line	 where	the  countth  previous	boundary  starts, and any text
	   copied to a buffer shall be in line mode.

	2. If the boundary was the first line of the  edit  buffer,  the  text
	   region  shall  consist of the first character in the edit buffer up
	   to but not including the starting character, and any text copied to
	   a buffer shall be in character mode.

	3. Otherwise,  the text region shall consist of the first character in
	   the countth previous section boundary up to but not	including  the
	   starting  character,	 and  any  text copied to a buffer shall be in
	   character mode.

       If not used as a motion command:

       Current line: Set to the line where the countth	previous  boundary  in
       the edit buffer starts.

       Current	column:	 Set  to  the  last column in which any portion of the
       first character of the countth previous boundary is displayed, or  col‐
       umn position 1 if the line is empty.

   Move to First Non-<blank> Position on Current Line
       Synopsis:

	      ^

       If used as a motion command:

	1. If  the  line has no non- <blank> non- <newline>s, or if the cursor
	   is at the first non- <blank> non- <newline> of the line,  it	 shall
	   be an error.

	2. If  the  cursor  is before the first non- <blank> non- <newline> of
	   the line, the text region shall be comprised of the current charac‐
	   ter,	 up  to,  but not including, the first non- <blank> non- <new‐
	   line> of the line.

	3. If the cursor is after the first non- <blank> non- <newline> of the
	   line, the text region shall be from the character before the start‐
	   ing cursor up to and including the first non-  <blank>  non-	 <new‐
	   line> of the line.

	4. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to non- <blank>.

   Current and Line Above
       Synopsis:

	      [count] _

       If  there  are  less  than count -1 lines after the current line in the
       edit buffer, it shall be an error.

       If used as a motion command:

	1. If count is less than 2, the text region shall be the current line.

	2. Otherwise, the text region shall include the starting line and  the
	   next count -1 lines.

	3. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       Current line: Set to current line + count -1.

       Current column: Set to non- <blank>.

   Move Back to Beginning of Sentence
       Synopsis:

	      [count] (

       Move  backward  to  the	beginning of a sentence. This command shall be
       equivalent to the [[ command, with the exception that  sentence	bound‐
       aries shall be used instead of section boundaries.

   Move Forward to Beginning of Sentence
       Synopsis:

	      [count] )

       Move  forward  to  the  beginning  of a sentence. This command shall be
       equivalent to the ]] command, with the exception that  sentence	bound‐
       aries shall be used instead of section boundaries.

   Move Back to Preceding Paragraph
       Synopsis:

	      [count] {

       Move  back  to  the  beginning of the preceding paragraph. This command
       shall be equivalent to the [[ command, with the	exception  that	 para‐
       graph boundaries shall be used instead of section boundaries.

   Move Forward to Next Paragraph
       Synopsis:

	      [count] }

       Move forward to the beginning of the next paragraph. This command shall
       be equivalent to the ]] command,	 with  the  exception  that  paragraph
       boundaries shall be used instead of section boundaries.

   Move to Specific Column Position
       Synopsis:

	      [count] |

       For  the purposes of this command, lines that are too long for the cur‐
       rent display and that have been folded shall be	treated	 as  having  a
       single, 1-based, number of columns.

       If  there are less than count columns in which characters from the cur‐
       rent line are displayed on the screen, count shall be  adjusted	to  be
       the  last  column  in which any portion of the line is displayed on the
       screen.

       If used as a motion command:

	1. If the line is empty, or the cursor character is the	 same  as  the
	   character on the countth column of the line, it shall be an error.

	2. If  the  cursor  is before the countth column of the line, the text
	   region shall be comprised of the current character, up to  but  not
	   including the character on the countth column of the line.

	3. If  the  cursor  is	after the countth column of the line, the text
	   region shall be from the character before the starting cursor up to
	   and including the character on the countth column of the line.

	4. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current	column:	 Set  to  the  last column in which any portion of the
       character that is displayed in the count column of  the	line  is  dis‐
       played.

   Reverse Find Character
       Synopsis:

	      [count] ,

       If the last F, f, T, or t command was F, f, T, or t, this command shall
       be equivalent to an f, F, t, or T command, respectively, with the spec‐
       ified count and the same search character.

       If there was no previous F, f, T, or t command, it shall be an error.

   Repeat
       Synopsis:

	      [count] .

       Repeat  the  last !, <, >, A, C, D, I, J, O, P, R, S, X, Y, a, c, d, i,
       o, p, r, s, x, y, or ~ command. It shall be an error if none  of	 these
       commands	 have  been executed. Commands (other than commands that enter
       text input mode) executed as a result  of  map  expansions,  shall  not
       change the value of the last repeatable command.

       Repeated	 commands  with	 associated  motion  commands shall repeat the
       motion command as well; however, any specified count shall replace  the
       count(s)	 that were originally specified to the repeated command or its
       associated motion command.

       If the motion component of the repeated command is f, F, t, or  T,  the
       repeated	 command shall not set the remembered search character for the
       ; and , commands.

       If the repeated command is p or P, and the buffer associated with  that
       command	was a numeric buffer named with a number less than 9, the buf‐
       fer associated with the repeated command shall be set to be the	buffer
       named by the name of the previous buffer logically incremented by 1.

       If the repeated character is a text input command, the input text asso‐
       ciated with that command is repeated literally:

	* Input characters are neither macro or abbreviation-expanded.

	* Input characters are not interpreted in any  special	way  with  the
	  exception  that <newline>, <carriage-return>, and <control>-T behave
	  as described in Input Mode Commands in vi .

       Current line: Set as described for the repeated command.

       Current column: Set as described for the repeated command.

   Find Regular Expression
       Synopsis:

	      /

       If the input line contains no non- <newline>s, it shall	be  equivalent
       to  a line containing only the last regular expression encountered. The
       enhanced regular expressions supported by vi are described  in  Regular
       Expressions in ex .

       Otherwise, the line shall be interpreted as one or more regular expres‐
       sions, optionally followed by an address offset or a vi z command.

       If the regular expression is not the last  regular  expression  on  the
       line,  or  if  a	 line  offset  or  z command is specified, the regular
       expression shall be terminated by an  unescaped	'/'  character,	 which
       shall  not  be  used  as part of the regular expression. If the regular
       expression is not the first regular expression on the line, it shall be
       preceded	 by zero or more <blank>s, a semicolon, zero or more <blank>s,
       and a leading '/' character, which shall not be interpreted as part  of
       the  regular  expression.  It  shall be an error to precede any regular
       expression with any characters other than these.

       Each search shall begin from the character after the first character of
       the  last  match	 (or, if it is the first search, after the cursor). If
       the wrapscan edit option is set, the search shall continue to the char‐
       acter  before  the  starting cursor character; otherwise, to the end of
       the edit buffer. It shall be an error if any search  fails  to  find  a
       match, and an informational message to this effect shall be displayed.

       An  optional  address  offset  (see Addressing in ex ) can be specified
       after the last regular expression by including a trailing '/' character
       after  the  regular expression and specifying the address offset.  This
       offset will be from the line containing the match for the last  regular
       expression  specified.  It  shall  be an error if the line offset would
       indicate a line address less than 1 or greater than the	last  line  in
       the edit buffer. An address offset of zero shall be supported. It shall
       be an error to follow the address offset with any other characters than
       <blank>s.

       If not used as a motion command, an optional z command (see Redraw Win‐
       dow ) can be specified after the last regular expression by including a
       trailing	 '/'  character	 after	the  regular  expression, zero or more
       <blank>s, a 'z', zero or more <blank>s, an  optional  new  window  edit
       option  value,  zero  or	 more  <blank>s, and a location character. The
       effect shall be as if the z command was executed after the  /  command.
       It  shall be an error to follow the z command with any other characters
       than <blank>s.

       The remembered search direction shall be set to forward.

       If used as a motion command:

	1. It shall be an error if the last match references the same  charac‐
	   ter in the edit buffer as the starting cursor.

	2. If  any  address  offset  is	 specified,  the  last	match shall be
	   adjusted by the specified offset as described previously.

	3. If the starting cursor is after the last match, then the  locations
	   of  the starting cursor and the last match in the edit buffer shall
	   be logically swapped.

	4. If any address offset is specified, the text region	shall  consist
	   of  all lines containing characters from the starting cursor to the
	   last match line, inclusive, and any text copied to a	 buffer	 shall
	   be in line mode.

	5. Otherwise,  if the starting line is empty or the starting cursor is
	   at or before the first non- <blank> non- <newline> of the  starting
	   line,  and the last match line is empty or the last match starts at
	   the first character of the last match line, the text	 region	 shall
	   consist of all lines containing characters from the starting cursor
	   to the line before the last match line,  inclusive,	and  any  text
	   copied to a buffer shall be in line mode.

	6. Otherwise, if the last match line is empty or the last match begins
	   at a character at or before the first non- <blank>  non-  <newline>
	   of  the  last match line, the region of text shall be from the cur‐
	   rent cursor to the last non- <newline> of the line before the  last
	   match  line, inclusive, and any text copied to a buffer shall be in
	   character mode.

	7. Otherwise, the region of text shall	be  from  the  current	cursor
	   (inclusive),	 to the first character of the last match (exclusive),
	   and any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: If a match is found, set to the last  matched  line  plus
       the address offset, if any; otherwise, unchanged.

       Current	column:	 Set  to  the  last column on which any portion of the
       first character in the last matched string is displayed, if a match  is
       found; otherwise, unchanged.

   Move to First Character in Line
       Synopsis:

	      0	 (zero)

       Move  to	 the  first  character	on the current line. The character '0'
       shall not be interpreted as a command if it is immediately preceded  by
       a digit.

       If used as a motion command:

	1. If  the  cursor  character  is  the first character in the line, it
	   shall be an error.

	2. The text region shall be from the character before the cursor char‐
	   acter up to and including the first character in the line.

	3. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: The last column in which any portion of the first char‐
       acter in the line is displayed, or if the line is empty, unchanged.

   Execute an ex Command
       Synopsis:

	      :

       Execute one or more ex commands.

       If any portion of the screen other than the last line of the screen was
       overwritten  by	any ex command (except shell), vi shall display a mes‐
       sage indicating that it is waiting for an  input	 from  the  user,  and
       shall  then  read a character. This action may also be taken for other,
       unspecified reasons.

       If the next character entered is a ':', another	ex  command  shall  be
       accepted and executed. Any other character shall cause the screen to be
       refreshed and vi shall return to command mode.

       Current line: As specified for the ex command.

       Current column: As specified for the ex command.

   Repeat Find
       Synopsis:

	      [count] ;

       This command shall be equivalent to the last F, f,  T,  or  t  command,
       with  the  specified count, and with the same search character used for
       the last F, f, T, or t command. If there was no previous F, f, T, or  t
       command, it shall be an error.

   Shift Left
       Synopsis:

	      [count] < motion

       If the motion command is the < command repeated:

	1. If there are less than count -1 lines after the current line in the
	   edit buffer, it shall be an error.

	2. The text region shall be from the current line, up to and including
	   the next count -1 lines.

       Shift  any  line	 in  the text region specified by the count and motion
       command one shiftwidth (see the ex shiftwidth option) toward the	 start
       of  the	line,  as  described  by the ex < command. The unshifted lines
       shall be copied to the unnamed buffer in line mode.

       Current line: If the motion was from the current cursor position toward
       the end of the edit buffer, unchanged. Otherwise, set to the first line
       in the edit buffer that is part of the text  region  specified  by  the
       motion command.

       Current column: Set to non- <blank>.

   Shift Right
       Synopsis:

	      [count] > motion

       If the motion command is the > command repeated:

	1. If there are less than count -1 lines after the current line in the
	   edit buffer, it shall be an error.

	2. The text region shall be from the current line, up to and including
	   the next count -1 lines.

       Shift  any  line	 with  characters  in the text region specified by the
       count and motion command one shiftwidth (see the ex shiftwidth  option)
       away  from the start of the line, as described by the ex > command. The
       unshifted lines shall be copied into the unnamed buffer in line mode.

       Current line: If the motion was from the current cursor position toward
       the end of the edit buffer, unchanged. Otherwise, set to the first line
       in the edit buffer that is part of the text  region  specified  by  the
       motion command.

       Current column: Set to non- <blank>.

   Scan Backwards for Regular Expression
       Synopsis:

	      ?

       Scan backwards; the ? command shall be equivalent to the / command (see
       Find Regular Expression ) with the following exceptions:

	1. The input prompt shall be a '?' .

	2. Each search shall begin from the character before the first charac‐
	   ter of the last match (or, if it is the first search, the character
	   before the cursor character).

	3. The search direction shall be from the cursor toward the  beginning
	   of  the  edit  buffer,  and	the  wrapscan edit option shall affect
	   whether the search wraps to the end of the edit buffer and  contin‐
	   ues.

	4. The remembered search direction shall be set to backward.

   Execute
       Synopsis:

	      @buffer

       If  the	buffer	is  specified  as @, the last buffer executed shall be
       used. If no previous buffer has been executed, it shall be an error.

       Behave as if the contents of the named buffer were entered as  standard
       input. After each line of a line-mode buffer, and all but the last line
       of a character mode buffer, behave as if a <newline>  were  entered  as
       standard input.

       If an error occurs during this process, an error message shall be writ‐
       ten, and no more characters resulting from the execution of  this  com‐
       mand shall be processed.

       If  a  count is specified, behave as if that count were entered as user
       input before the characters from the @ buffer were entered.

       Current line: As specified for the individual commands.

       Current column: As specified for the individual commands.

   Reverse Case
       Synopsis:

	      [count] ~

       Reverse the case of the current character and the next count -1 charac‐
       ters,  such  that lowercase characters that have uppercase counterparts
       shall be changed to uppercase characters, and uppercase characters that
       have  lowercase	counterparts shall be changed to lowercase characters,
       as prescribed by the current locale.   No  other	 characters  shall  be
       affected by this command.

       If there are less than count -1 characters after the cursor in the edit
       buffer, count shall be adjusted to the number of characters  after  the
       cursor in the edit buffer minus 1.

       For  the	 purposes  of  this command, the next character after the last
       non- <newline> on the line shall be the next character in the edit buf‐
       fer.

       Current	line:  Set  to	the  line including the ( count-1)th character
       after the cursor.

       Current column: Set to the last column in which any portion  of	the  (
       count-1)th character after the cursor is displayed.

   Append
       Synopsis:

	      [count] a

       Enter  text input mode after the current cursor position. No characters
       already in the edit buffer shall be affected by this command.  A	 count
       shall  cause  the  input text to be appended count -1 more times to the
       end of the input.

       Current line/column: As specified for  the  text	 input	commands  (see
       Input Mode Commands in vi ).

   Append at End-of-Line
       Synopsis:

	      [count] A

       This command shall be equivalent to the vi command:

	      $ [ count ] a

       (see Append ).

   Move Backward to Preceding Word
       Synopsis:

	      [count] b

       With the exception that words are used as the delimiter instead of big‐
       words, this command shall be equivalent to the B command.

   Move Backward to Preceding Bigword
       Synopsis:

	      [count] B

       If the edit buffer is empty or the cursor is on the first character  of
       the  edit  buffer,  it  shall  be an error. If less than count bigwords
       begin between the cursor and the start of the edit buffer, count	 shall
       be  adjusted to the number of bigword beginnings between the cursor and
       the start of the edit buffer.

       If used as a motion command:

	1. The text region shall be from the first character  of  the  countth
	   previous bigword beginning up to but not including the cursor char‐
	   acter.

	2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the line containing the current column.

       Current column: Set to the last column upon which any part of the first
       character of the countth previous bigword is displayed.

   Change
       Synopsis:

	      [buffer][count] c motion

       If the motion command is the c command repeated:

	1. The buffer text shall be in line mode.

	2. If there are less than count -1 lines after the current line in the
	   edit buffer, it shall be an error.

	3. The text region shall be from the current line up to and  including
	   the next count -1 lines.

       Otherwise,  the	buffer text mode and text region shall be as specified
       by the motion command.

       The replaced text shall be copied into buffer, if specified,  and  into
       the unnamed buffer. If the text to be replaced contains characters from
       more than a single line, or the	buffer	text  is  in  line  mode,  the
       replaced text shall be copied into the numeric buffers as well.

       If the buffer text is in line mode:

	1. Any	lines  that contain characters in the region shall be deleted,
	   and the editor shall enter text input mode at the  beginning	 of  a
	   new line which shall replace the first line deleted.

	2. If  the  autoindent edit option is set, autoindent characters equal
	   to the autoindent characters on the first  line  deleted  shall  be
	   inserted as if entered by the user.

       Otherwise,  if  characters from more than one line are in the region of
       text:

	1. The text shall be deleted.

	2. Any text remaining in the last line in the  text  region  shall  be
	   appended  to the first line in the region, and the last line in the
	   region shall be deleted.

	3. The editor shall enter text input mode after the last character not
	   deleted  from the first line in the text region, if any; otherwise,
	   on the first column of the first line in the region.

       Otherwise:

	1. If the glyph for '$' is smaller than the region,  the  end  of  the
	   region shall be marked with a '$' .

	2. The	editor	shall enter text input mode, overwriting the region of
	   text.

       Current line/column: As specified for  the  text	 input	commands  (see
       Input Mode Commands in vi ).

   Change to End-of-Line
       Synopsis:

	      [buffer][count] C

       This command shall be equivalent to the vi command:

	      [buffer][count] c$

       See the c command.

   Delete
       Synopsis:

	      [buffer][count] d motion

       If the motion command is the d command repeated:

	1. The buffer text shall be in line mode.

	2. If there are less than count -1 lines after the current line in the
	   edit buffer, it shall be an error.

	3. The text region shall be from the current line up to and  including
	   the next count -1 lines.

       Otherwise,  the	buffer text mode and text region shall be as specified
       by the motion command.

       If in open mode, and the current line is deleted, and the line  remains
       on  the display, an '@' character shall be displayed as the first glyph
       of that line.

       Delete the region of text into  buffer,	if  specified,	and  into  the
       unnamed buffer. If the text to be deleted contains characters from more
       than a single line, or the buffer text is in  line  mode,  the  deleted
       text shall be copied into the numeric buffers, as well.

       Current	line:  Set  to	the first text region line that appears in the
       edit buffer, unless that line has been deleted, in which case it	 shall
       be  set to the last line in the edit buffer, or line 1 if the edit buf‐
       fer is empty.

       Current column:

	1. If the line is empty, set to column position 1.

	2. Otherwise, if the buffer text is in line mode  or  the  motion  was
	   from the cursor toward the end of the edit buffer:

	    a. If  a  character from the current line is displayed in the cur‐
	       rent column, set to the last column that displays  any  portion
	       of that character.

	    b. Otherwise,  set	to the last column in which any portion of any
	       character in the line is displayed.

	3. Otherwise, if a character is displayed in the column that began the
	   text	 region,  set  to the last column that displays any portion of
	   that character.

	4. Otherwise, set to the last column in which any portion of any char‐
	   acter in the line is displayed.

   Delete to End-of-Line
       Synopsis:

	      [buffer] D

       Delete  the  text  from	the current position to the end of the current
       line; equivalent to the vi command:

	      [buffer] d$

   Move to End-of-Word
       Synopsis:

	      [count] e

       With the exception that words are  used	instead	 of  bigwords  as  the
       delimiter, this command shall be equivalent to the E command.

   Move to End-of-Bigword
       Synopsis:

	      [count] E

       If  the	edit  buffer is empty it shall be an error. If less than count
       bigwords end between the cursor and the end of the edit	buffer,	 count
       shall  be  adjusted to the number of bigword endings between the cursor
       and the end of the edit buffer.

       If used as a motion command:

	1. The text region shall be from the last  character  of  the  countth
	   next bigword up to and including the cursor character.

	2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the line containing the current column.

       Current	column: Set to the last column upon which any part of the last
       character of the countth next bigword is displayed.

   Find Character in Current Line (Forward)
       Synopsis:

	      [count] f character

       It shall be an error if count occurrences of the character do not occur
       after the cursor in the line.

       If used as a motion command:

	1. The text range shall be from the cursor character up to and includ‐
	   ing the countth occurrence of the  specified	 character  after  the
	   cursor.

	2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current	column:	 Set  to  the  last column in which any portion of the
       countth occurrence of the specified character after the cursor  appears
       in the line.

   Find Character in Current Line (Reverse)
       Synopsis:

	      [count] F character

       It shall be an error if count occurrences of the character do not occur
       before the cursor in the line.

       If used as a motion command:

	1. The text region shall be from the countth occurrence of the	speci‐
	   fied character before the cursor, up to, but not including the cur‐
	   sor character.

	2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to the last column in  which	 any  portion  of  the
       countth occurrence of the specified character before the cursor appears
       in the line.

   Move to Line
       Synopsis:

	      [count] G

       If count is not specified, it shall default to the  last	 line  of  the
       edit buffer. If count is greater than the last line of the edit buffer,
       it shall be an error.

       If used as a motion command:

	1. The text region shall be from the cursor line up to	and  including
	   the specified line.

	2. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       Current	line:  Set to count if count is specified; otherwise, the last
       line.

       Current column: Set to non- <blank>.

   Move to Top of Screen
       Synopsis:

	      [count] H

       If the beginning of the line count greater than the first line of which
       any  portion  appears  on  the  display	does not exist, it shall be an
       error.

       If used as a motion command:

	1. If in open mode, the text region shall be the current line.

	2. Otherwise, the text region shall be from the starting  line	up  to
	   and including (the first line of the display + count -1).

	3. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       If  in  open  mode,  this  command shall set the current column to non-
       <blank> and do nothing else.

       Otherwise, it shall set the current line and current column as follows.

       Current line: Set to (the first line of the display + count -1).

       Current column: Set to non- <blank>.

   Insert Before Cursor
       Synopsis:

	      [count] i

       Enter text input mode before the current cursor position. No characters
       already	in  the edit buffer shall be affected by this command. A count
       shall cause the input text to be appended count -1 more	times  to  the
       end of the input.

       Current	line/column:  As  specified  for  the text input commands (see
       Input Mode Commands in vi ).

   Insert at Beginning of Line
       Synopsis:

	      [count] I

       This command shall be equivalent to the vi command ^[ count] i.

   Join
       Synopsis:

	      [count] J

       If the current line is the last line in the edit buffer, it shall be an
       error.

       This  command  shall  be	 equivalent  to	 the  ex  join command with no
       addresses, and an ex command count value of 1 if count was  not	speci‐
       fied or if a count of 1 was specified, and an ex command count value of
       count -1 for any other value of count, except that the current line and
       column shall be set as follows.

       Current line: Unchanged.

       Current	column:	 The last column in which any portion of the character
       following the last character in the initial line is displayed,  or  the
       last non- <newline> in the line if no characters were appended.

   Move to Bottom of Screen
       Synopsis:

	      [count] L

       If the beginning of the line count less than the last line of which any
       portion appears on the display does not exist, it shall be an error.

       If used as a motion command:

	1. If in open mode, the text region shall be the current line.

	2. Otherwise, the text region shall include all lines from the	start‐
	   ing cursor line to (the last line of the display -( count -1)).

	3. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

	1. If  in open mode, this command shall set the current column to non-
	   <blank> and do nothing else.

	2. Otherwise, it shall set the current line and current column as fol‐
	   lows.

       Current line: Set to (the last line of the display -( count -1)).

       Current column: Set to non- <blank>.

   Mark Position
       Synopsis:

	      m letter

       This command shall be equivalent to the ex mark command with the speci‐
       fied character as an argument.

   Move to Middle of Screen
       Synopsis:

	      M

       The middle line of the display shall be calculated as follows:

	      (the top line of the display) + (((number of lines displayed) +1) /2) -1

       If used as a motion command:

	1. If in open mode, the text region shall be the current line.

	2. Otherwise, the text region shall include all lines from the	start‐
	   ing cursor line up to and including the middle line of the display.

	3. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       If  in  open  mode,  this  command shall set the current column to non-
       <blank> and do nothing else.

       Otherwise, it shall set the current line and current column as follows.

       Current line: Set to the middle line of the display.

       Current column: Set to non- <blank>.

   Repeat Regular Expression Find (Forward)
       Synopsis:

	      n

       If the remembered search direction was forward, the n command shall  be
       equivalent  to the vi / command with no characters entered by the user.
       Otherwise, it shall be equivalent to the vi ? command with  no  charac‐
       ters entered by the user.

       If  the	n  command is used as a motion command for the !  command, the
       editor shall not enter text input mode on the last line on the  screen,
       and  shall  behave as if the user entered a single '!' character as the
       text input.

   Repeat Regular Expression Find (Reverse)
       Synopsis:

	      N

       Scan for the next match of the last pattern given to / or ?, but in the
       reverse direction; this is the reverse of n.

       If  the remembered search direction was forward, the N command shall be
       equivalent to the vi ? command with no characters entered by the	 user.
       Otherwise,  it  shall be equivalent to the vi / command with no charac‐
       ters entered by the user. If the N command is used as a motion  command
       for  the	 !  command, the editor shall not enter text input mode on the
       last line on the screen, and shall behave as if the user entered a sin‐
       gle ! character as the text input.

   Insert Empty Line Below
       Synopsis:

	      o

       Enter text input mode in a new line appended after the current line.  A
       count shall cause the input text to be appended count -1 more times  to
       the  end	 of  the  already  added  text,	 each  time starting on a new,
       appended line.

       Current line/column: As specified for  the  text	 input	commands  (see
       Input Mode Commands in vi ).

   Insert Empty Line Above
       Synopsis:

	      O

       Enter  text  input mode in a new line inserted before the current line.
       A count shall cause the input text to be appended count -1  more	 times
       to  the	end  of	 the  already added text, each time starting on a new,
       appended line.

       Current line/column: As specified for  the  text	 input	commands  (see
       Input Mode Commands in vi ).

   Put from Buffer Following
       Synopsis:

	      [buffer] p

       If no buffer is specified, the unnamed buffer shall be used.

       If  the	buffer	text is in line mode, the text shall be appended below
       the current line, and each line of the buffer shall become a  new  line
       in  the edit buffer. A count shall cause the buffer text to be appended
       count -1 more times to the end of the already  added  text,  each  time
       starting on a new, appended line.

       If  the	buffer	text  is in character mode, the text shall be appended
       into the current line after the cursor, and each	 line  of  the	buffer
       other  than the first and last shall become a new line in the edit buf‐
       fer. A count shall cause the buffer text to be appended count  -1  more
       times  to  the  end of the already added text, each time starting after
       the last added character.

       Current line: If the buffer text is in line mode, set the line to  line
       +1; otherwise, unchanged.

       Current column: If the buffer text is in line mode:

	1. If  there is a non- <blank> in the first line of the buffer, set to
	   the last column on which any portion of the first non-  <blank>  in
	   the line is displayed.

	2. If there is no non- <blank> in the first line of the buffer, set to
	   the last column on which any portion of the last non- <newline>  in
	   the first line of the buffer is displayed.

       If the buffer text is in character mode:

	1. If the text in the buffer is from more than a single line, then set
	   to the last column on which any portion of the first character from
	   the buffer is displayed.

	2. Otherwise,  if  the	buffer	is the unnamed buffer, set to the last
	   column on which any portion of the last character from  the	buffer
	   is displayed.

	3. Otherwise,  set  to	the  first  column on which any portion of the
	   first character from the buffer is displayed.

   Put from Buffer Before
       Synopsis:

	      [buffer] P

       If no buffer is specified, the unnamed buffer shall be used.

       If the buffer text is in line mode, the text shall  be  inserted	 above
       the  current  line, and each line of the buffer shall become a new line
       in the edit buffer. A count shall cause the buffer text to be  appended
       count  -1  more	times  to the end of the already added text, each time
       starting on a new, appended line.

       If the buffer text is in character mode, the  text  shall  be  inserted
       into  the  current  line before the cursor, and each line of the buffer
       other than the first and last shall become a new line in the edit  buf‐
       fer.  A	count shall cause the buffer text to be appended count -1 more
       times to the end of the already added text, each	 time  starting	 after
       the last added character.

       Current line: Unchanged.

       Current column: If the buffer text is in line mode:

	1. If  there is a non- <blank> in the first line of the buffer, set to
	   the last column on which any portion	 of  that  character  is  dis‐
	   played.

	2. If there is no non- <blank> in the first line of the buffer, set to
	   the last column on which any portion of the last non- <newline>  in
	   the first line of the buffer is displayed.

       If the buffer text is in character mode:

	1. If  the  buffer  is	the  unnamed buffer, set to the last column on
	   which any portion of the last character from	 the  buffer  is  dis‐
	   played.

	2. Otherwise,  set  to	the  first  column on which any portion of the
	   first character from the buffer is displayed.

   Enter ex Mode
       Synopsis:

	      Q

       Leave visual or open mode and enter ex command mode.

       Current line: Unchanged.

       Current column: Unchanged.

   Replace Character
       Synopsis:

	      [count] r character

       Replace the count characters at and after the cursor with the specified
       character.  If  there  are less than count non- <newline>s at and after
       the cursor on the line, it shall be an error.

       If character is <control>-V, any next character other  than  the	 <new‐
       line>  shall  be	 stripped of any special meaning and used as a literal
       character.

       If character is <ESC>, no replacement shall be  made  and  the  current
       line and current column shall be unchanged.

       If  character  is <carriage-return> or <newline>, count new lines shall
       be appended to the current line. All but the last of these lines	 shall
       be  empty. count characters at and after the cursor shall be discarded,
       and any remaining characters after the cursor in the current line shall
       be moved to the last of the new lines. If the autoindent edit option is
       set, they shall be preceded by the same number of autoindent characters
       found on the line from which the command was executed.

       Current	line:  Unchanged  unless  the replacement character is a <car‐
       riage-return> or <newline>, in which case it shall be  set  to  line  +
       count.

       Current	column:	 Set to the last column position on which a portion of
       the last replaced character is displayed, or if the replacement charac‐
       ter caused new lines to be created, set to non- <blank>.

   Replace Characters
       Synopsis:

	      R

       Enter text input mode at the current cursor position possibly replacing
       text on the current line. A count shall cause  the  input  text	to  be
       appended count -1 more times to the end of the input.

       Current	line/column:  As  specified  for  the text input commands (see
       Input Mode Commands in vi ).

   Substitute Character
       Synopsis:

	      [buffer][count] s

       This command shall be equivalent to the vi command:

	      [buffer][count] c<space>

   Substitute Lines
       Synopsis:

	      [buffer][count] S

       This command shall be equivalent to the vi command:

	      [buffer][count] c_

   Move Cursor to Before Character (Forward)
       Synopsis:

	      [count] t character

       It shall be an error if count occurrences of the character do not occur
       after the cursor in the line.

       If used as a motion command:

	1. The	text  region  shall be from the cursor up to but not including
	   the countth occurrence of the specified character after the cursor.

	2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to the last column in  which	 any  portion  of  the
       character  before  the  countth	occurrence  of the specified character
       after the cursor appears in the line.

   Move Cursor to After Character (Reverse)
       Synopsis:

	      [count] T character

       It shall be an error if count occurrences of the character do not occur
       before the cursor in the line.

       If used as a motion command:

	1. If  the  character before the cursor is the specified character, it
	   shall be an error.

	2. The text region shall be from the character before the cursor up to
	   but not including the countth occurrence of the specified character
	   before the cursor.

	3. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to the last column in  which	 any  portion  of  the
       character  after	 the  countth  occurrence  of  the specified character
       before the cursor appears in the line.

   Undo
       Synopsis:

	      u

       This command shall be equivalent to the ex undo command except that the
       current line and current column shall be set as follows:

       Current line: Set to the first line added or changed if any; otherwise,
       move to the line preceding any deleted text if one  exists;  otherwise,
       move to line 1.

       Current	column:	 If  undoing  an  ex  command,	set  to the first non-
       <blank>.

       Otherwise, if undoing a text input command:

	1. If the command was a C, c, O, o, R, S, or s	command,  the  current
	   column  shall  be set to the value it held when the text input com‐
	   mand was entered.

	2. Otherwise, set to the last column in which any portion of the first
	   character after the deleted text is displayed, or, if no non- <new‐
	   line>s follow the text deleted from this line, set to the last col‐
	   umn	in which any portion of the last non- <newline> in the line is
	   displayed, or 1 if the line is empty.

       Otherwise, if a single  line  was  modified  (that  is,	not  added  or
       deleted) by the u command:

	1. If  text  was added or changed, set to the last column in which any
	   portion of the first character added or changed is displayed.

	2. If text was deleted, set to the last column in which any portion of
	   the	first character after the deleted text is displayed, or, if no
	   non- <newline>s follow the deleted text, set to the last column  in
	   which  any  portion	of the last non- <newline> in the line is dis‐
	   played, or 1 if the line is empty.

       Otherwise, set to non- <blank>.

   Undo Current Line
       Synopsis:

	      U

       Restore the current line to  its	 state	immediately  before  the  most
       recent time that it became the current line.

       Current line: Unchanged.

       Current	column:	 Set to the first column in the line in which any por‐
       tion of the first character in the line is displayed.

   Move to Beginning of Word
       Synopsis:

	      [count] w

       With the exception that words are used as the delimiter instead of big‐
       words, this command shall be equivalent to the W command.

   Move to Beginning of Bigword
       Synopsis:

	      [count] W

       If  the	edit  buffer is empty, it shall be an error. If there are less
       than count bigwords between the cursor and the end of the edit  buffer,
       count  shall  be adjusted to move the cursor to the last bigword in the
       edit buffer.

       If used as a motion command:

	1. If the associated command is c, count is 1, and the cursor is on  a
	   <blank>,  the  region of text shall be the current character and no
	   further action shall be taken.

	2. If there are less than count bigwords between the  cursor  and  the
	   end	of  the	 edit  buffer, then the command shall succeed, and the
	   region of text shall include the last character of the edit buffer.

	3. If there are <blank>s or an end-of-line that	 precede  the  countth
	   bigword,  and the associated command is c, the region of text shall
	   be up to and including the  last  character	before	the  preceding
	   <blank>s or end-of-line.

	4. If  there  are <blank>s or an end-of-line that precede the bigword,
	   and the associated command is d or y, the region of text  shall  be
	   up  to  and including the last <blank> before the start of the big‐
	   word or end-of-line.

	5. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

	1. If the cursor is on the last character of the edit buffer, it shall
	   be an error.

       Current line: Set to the line containing the current column.

       Current	column:	 Set to the last column in which any part of the first
       character of the countth next bigword is displayed.

   Delete Character at Cursor
       Synopsis:

	      [buffer][count] x

       Delete the count characters at and after	 the  current  character  into
       buffer, if specified, and into the unnamed buffer.

       If  the	line  is  empty,  it shall be an error. If there are less than
       count non- <newline>s at and after the  cursor  on  the	current	 line,
       count  shall  be adjusted to the number of non- <newline>s at and after
       the cursor.

       Current line: Unchanged.

       Current column: If the line is empty, set to column position 1.	Other‐
       wise, if there were count or less non- <newline>s at and after the cur‐
       sor on the current line, set to the last column that displays any  part
       of the last non- <newline> of the line. Otherwise, unchanged.

   Delete Character Before Cursor
       Synopsis:

	      [buffer][count] X

       Delete  the  count characters before the current character into buffer,
       if specified, and into the unnamed buffer.

       If there are no characters before the current character on the  current
       line, it shall be an error. If there are less than count previous char‐
       acters on the current line, count shall be adjusted to  the  number  of
       previous characters on the line.

       Current line: Unchanged.

       Current column: Set to (current column - the width of the deleted char‐
       acters).

   Yank
       Synopsis:

	      [buffer][count] y motion

       Copy (yank) the region of text into buffer, if specified, and into  the
       unnamed buffer.

       If the motion command is the y command repeated:

	1. The buffer shall be in line mode.

	2. If there are less than count -1 lines after the current line in the
	   edit buffer, it shall be an error.

	3. The text region shall be from the current line up to and  including
	   the next count -1 lines.

       Otherwise,  the	buffer text mode and text region shall be as specified
       by the motion command.

       Current line: If the motion was from the current cursor position toward
       the end of the edit buffer, unchanged. Otherwise, set to the first line
       in the edit buffer that is part of the text  region  specified  by  the
       motion command.

       Current column:

	1. If  the  motion was from the current cursor position toward the end
	   of the edit buffer, unchanged.

	2. Otherwise, if the current line is empty, set to column position 1.

	3. Otherwise, set to the last column that displays  any	 part  of  the
	   first  character in the file that is part of the text region speci‐
	   fied by the motion command.

   Yank Current Line
       Synopsis:

	      [buffer][count] Y

       This command shall be equivalent to the vi command:

	      [buffer][count] y_

   Redraw Window
       If in open mode, the z command shall have the Synopsis:

       Synopsis:

	      [count] z

       If count is not specified, it shall default to the window  edit	option
       -1.  The z command shall be equivalent to the ex z command, with a type
       character of = and a count of count -2, except that  the	 current  line
       and  current column shall be set as follows, and the window edit option
       shall not be affected. If the calculation for the count argument	 would
       result  in  a  negative	number, the count argument to the ex z command
       shall be zero. A blank line shall be written after  the	last  line  is
       written.

       Current line: Unchanged.

       Current column: Unchanged.

       If not in open mode, the z command shall have the following Synopsis:

       Synopsis:

	      [line] z [count] character

       If  line	 is  not  specified, it shall default to the current line.  If
       line is specified, but is greater than the number of lines in the  edit
       buffer, it shall default to the number of lines in the edit buffer.

       If count is specified, the value of the window edit option shall be set
       to count (as described in the ex window command), and the screen	 shall
       be redrawn.

       line shall be placed as specified by the following characters:

       <newline>, <carriage-return>

	      Place  the  beginning  of the line on the first line of the dis‐
	      play.

       .      Place the beginning of the line in the center  of	 the  display.
	      The  middle line of the display shall be calculated as described
	      for the M command.

       -      Place an unspecified portion of the line on the last line of the
	      display.

       +      If line was specified, equivalent to the <newline> case. If line
	      was not specified, display a screen where the first line of  the
	      display  shall  be (current last line) +1. If there are no lines
	      after the last line in the display, it shall be an error.

       ^      If line was specified, display a screen where the last  line  of
	      the  display  shall  contain an unspecified portion of the first
	      line of a display that had an unspecified portion of the	speci‐
	      fied  line  on the last line of the display. If this calculation
	      results in a line before the beginning of the edit buffer,  dis‐
	      play the first screen of the edit buffer.

       Otherwise,  display  a  screen where the last line of the display shall
       contain an unspecified portion of (current first	 line  -1).   If  this
       calculation  results in a line before the beginning of the edit buffer,
       it shall be an error.

       Current line: If line and the '^' character were specified:

	1. If the first screen was  displayed  as  a  result  of  the  command
	   attempting  to  display lines before the beginning of the edit buf‐
	   fer: if the first screen was already displayed,  unchanged;	other‐
	   wise, set to (current first line -1).

	2. Otherwise, set to the last line of the display.

       If  line and the '+' character were specified, set to the first line of
       the display.

       Otherwise, if line was specified, set to line.

       Otherwise, unchanged.

       Current column: Set to non- <blank>.

   Exit
       Synopsis:

	      ZZ

       This command shall  be  equivalent  to  the  ex	xit  command  with  no
       addresses, trailing !, or filename (see the ex xit command).

   Input Mode Commands in vi
       In  text	 input mode, the current line shall consist of zero or more of
       the following categories, plus the terminating <newline>:

	1. Characters preceding the text input entry point

       Characters in this category shall not be	 modified  during  text	 input
       mode.

	2. autoindent characters

       autoindent  characters  shall  be automatically inserted into each line
       that is created in text input mode, either as a result  of  entering  a
       <newline>  or  <carriage-return>	 while	in  text  input mode, or as an
       effect of the command itself; for example, O or o (see the  ex  autoin‐
       dent command), as if entered by the user.

       It  shall  be  possible	to  erase autoindent characters with the <con‐
       trol>-D command; it is unspecified whether they can be erased by	 <con‐
       trol>-H,	 <control>-U, and <control>-W characters.  Erasing any autoin‐
       dent character turns the glyph into erase-columns and deletes the char‐
       acter  from  the edit buffer, but does not change its representation on
       the screen.

	3. Text input characters

       Text input characters are the characters entered by the	user.  Erasing
       any text input character turns the glyph into erase-columns and deletes
       the character from the edit buffer, but does not change its representa‐
       tion on the screen.

       Each  text  input  character  entered by the user (that does not have a
       special meaning) shall be treated as follows:

	       a. The text input character shall be appended to the last char‐
		  acter	 in  the  edit buffer from the first, second, or third
		  categories.

	       b. If there are no erase-columns on the screen, the text	 input
		  command was the R command, and characters in the fifth cate‐
		  gory from the original line follow the cursor, the next such
		  character  shall  be	deleted	 from  the edit buffer. If the
		  slowopen edit option is not set, the corresponding glyph  on
		  the screen shall become erase-columns.

	       c. If there are erase-columns on the screen, as many columns as
		  they occupy, or as are necessary, shall  be  overwritten  to
		  display  the text input character. (If only part of a multi-
		  column glyph is overwritten, the remainder shall be left  on
		  the  screen, and continue to be treated as erase-columns; it
		  is unspecified whether the remainder of the glyph  is	 modi‐
		  fied in any way.)

	       d. If additional display line columns are needed to display the
		  text input character:

		   1. If the slowopen edit option is set, the text input char‐
		      acters  shall  be	 displayed  on subsequent display line
		      columns, overwriting any characters displayed  in	 those
		      columns.

		   2. Otherwise,  any  characters  currently  displayed	 on or
		      after the column on the  display	line  where  the  text
		      input character is to be displayed shall be pushed ahead
		      the number of display line columns necessary to  display
		      the rest of the text input character.

	4. Erase-columns

       Erase-columns are not logically part of the edit buffer, appearing only
       on the screen, and may be overwritten on the screen by subsequent  text
       input characters. When text input mode ends, all erase-columns shall no
       longer appear on the screen.

       Erase-columns are initially the region of text specified by the c  com‐
       mand  (see  Change ); however, erasing autoindent or text input charac‐
       ters causes the glyphs of the erased characters to be treated as erase-
       columns.

	5. Characters following the text region for the c command, or the text
	   input entry point for all other commands

       Characters in this category shall not be	 modified  during  text	 input
       mode,  except  as  specified in category 3.b. for the R text input com‐
       mand, or as <blank>s deleted when a <newline> or	 <carriage-return>  is
       entered.

       It  is  unspecified whether it is an error to attempt to erase past the
       beginning of a line that was created by the entry  of  a	 <newline>  or
       <carriage-return>  during  text	input mode. If it is not an error, the
       editor shall behave as if the erasing character was entered immediately
       after  the  last text input character entered on the previous line, and
       all of the non- <newline>s on the current  line	shall  be  treated  as
       erase-columns.

       When  text  input mode is entered, or after a text input mode character
       is entered (except as specified for the special characters below),  the
       cursor shall be positioned as follows:

	1. On  the first column that displays any part of the first erase-col‐
	   umn, if one exists

	2. Otherwise, if the slowopen edit option is set, on the first display
	   line column after the last character in the first, second, or third
	   categories, if one exists

	3. Otherwise, the first column that displays any  part	of  the	 first
	   character in the fifth category, if one exists

	4. Otherwise,  the display line column after the last character in the
	   first, second, or third categories, if one exists

	5. Otherwise, on column position 1

       The characters that are updated on the screen during  text  input  mode
       are  unspecified,  other	 than that the last text input character shall
       always be updated, and, if the slowopen edit option  is	not  set,  the
       current cursor character shall always be updated.

       The  following specifications are for command characters entered during
       text input mode.

   NUL
       Synopsis:

	      NUL

       If the first character of the text input is a NUL,  the	most  recently
       input  text  shall  be  input  as if entered by the user, and then text
       input mode shall be exited. The text shall be input literally; that is,
       characters  are	neither	 macro	or  abbreviation expanded, nor are any
       characters interpreted  in  any	special	 manner.   It  is  unspecified
       whether implementations shall support more than 256 bytes of remembered
       input text.

   <control>-D
       Synopsis:

	      <control>-D

       The <control>-D character shall have no special meaning	when  in  text
       input  mode for a line-oriented command (see Command Descriptions in vi
       ).

       This command need not be supported on block-mode terminals.

       If the cursor does not follow an autoindent character, or an autoindent
       character and a '0' or '^' character:

	1. If  the  cursor  is in column position 1, the <control>-D character
	   shall be discarded and no further action taken.

	2. Otherwise, the <control>-D character shall have no special meaning.

       If the last input character was a '0', the cursor  shall	 be  moved  to
       column position 1.

       Otherwise,  if  the last input character was a '^', the cursor shall be
       moved to column position 1. In addition, the autoindent level  for  the
       next  input  line  shall	 be  derived from the same line from which the
       autoindent level for the current input line was derived.

       Otherwise, the cursor shall be moved back to the column after the  pre‐
       vious shiftwidth (see the ex shiftwidth command) boundary.

       All  of	the glyphs on columns between the starting cursor position and
       (inclusively) the ending cursor position shall become erase-columns  as
       described in Input Mode Commands in vi .

       Current line: Unchanged.

       Current	column:	 Set  to 1 if the <control>-D was preceded by a '^' or
       '0' ; otherwise, set to (column -1) -((column -2) % shiftwidth).

   <control>-H
       Synopsis:

	      <control>-H

       If in text input mode for a line-oriented command,  and	there  are  no
       characters  to  erase,  text input mode shall be terminated, no further
       action shall be done for this command, and the current line and	column
       shall be unchanged.

       If there are characters other than autoindent characters that have been
       input on the current line before the cursor, the cursor shall move back
       one character.

       Otherwise,  if  there  are  autoindent  characters  on the current line
       before the cursor, it is implementation-defined whether the <control>-H
       command	is an error or if the cursor moves back one autoindent charac‐
       ter.

       Otherwise, if the cursor is in column position 1 and there are previous
       lines  that  have  been input, it is implementation-defined whether the
       <control>-H command is an error or if  it  is  equivalent  to  entering
       <control>-H after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All  of	the glyphs on columns between the starting cursor position and
       (inclusively) the ending cursor position shall become erase-columns  as
       described in Input Mode Commands in vi .

       The current erase character (see stty) shall cause an equivalent action
       to the <control>-H command, unless the  previously  inserted  character
       was  a  backslash,  in which case it shall be as if the literal current
       erase character had been inserted instead of the backslash.

       Current line: Unchanged, unless previously input lines are  erased,  in
       which case it shall be set to line -1.

       Current	column:	 Set  to the first column that displays any portion of
       the character backed up over.

   <newline>
       Synopsis:

	      <newline>

	      <carriage-return>

	      <control>-J

	      <control>-M

       If input was part of a line-oriented command, text input mode shall  be
       terminated and the command shall continue execution with the input pro‐
       vided.

       Otherwise, terminate the current line. If there are no characters other
       than  autoindent	 characters  on	 the  line, all characters on the line
       shall be discarded. Otherwise, it is unspecified whether the autoindent
       characters in the line are modified by entering these characters.

       Continue text input mode on a new line appended after the current line.
       If the slowopen edit option is set, the lines on the screen  below  the
       current	line  shall not be pushed down, but the first of them shall be
       cleared and shall appear to be overwritten. Otherwise, the lines of the
       screen below the current line shall be pushed down.

       If  the autoindent edit option is set, an appropriate number of autoin‐
       dent characters shall be added as a prefix to the line as described  by
       the ex autoindent edit option.

       All  columns  after  the cursor that are erase-columns (as described in
       Input Mode Commands in vi ) shall be discarded.

       If the autoindent edit option is set, all <blank>s immediately  follow‐
       ing the cursor shall be discarded.

       All  remaining  characters after the cursor shall be transferred to the
       new line, positioned after any autoindent characters.

       Current line: Set to current line +1.

       Current column: Set to the first column that displays  any  portion  of
       the first character after the autoindent characters on the new line, if
       any, or the first column position after the last autoindent  character,
       if any, or column position 1.

   <control>-T
       Synopsis:

	      <control>-T

       The  <control>-T	 character  shall have no special meaning when in text
       input mode for a line-oriented command (see Command Descriptions in  vi
       ).

       This command need not be supported on block-mode terminals.

       Behave  as if the user entered the minimum number of <blank>s necessary
       to move the cursor forward  to  the  column  position  after  the  next
       shiftwidth (see the ex shiftwidth command) boundary.

       Current line: Unchanged.

       Current	 column:   Set	to  column  +  shiftwidth  -  ((column	-1)  %
       shiftwidth).

   <control>-U
       Synopsis:

	      <control>-U

       If there are characters other than autoindent characters that have been
       input  on  the current line before the cursor, the cursor shall move to
       the first character input after the autoindent characters.

       Otherwise, if there are	autoindent  characters	on  the	 current  line
       before the cursor, it is implementation-defined whether the <control>-U
       command is an error or if the cursor moves to the first column position
       on the line.

       Otherwise, if the cursor is in column position 1 and there are previous
       lines that have been input, it is  implementation-defined  whether  the
       <control>-U  command  is	 an  error  or if it is equivalent to entering
       <control>-U after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All of the glyphs on columns between the starting cursor	 position  and
       (inclusively)  the ending cursor position shall become erase-columns as
       described in Input Mode Commands in vi .

       The current kill character (see stty) shall cause an equivalent	action
       to  the	<control>-U  command, unless the previously inserted character
       was a backslash, in which case it shall be as if	 the  literal  current
       kill character had been inserted instead of the backslash.

       Current	line:  Unchanged, unless previously input lines are erased, in
       which case it shall be set to line -1.

       Current column: Set to the first column that displays  any  portion  of
       the last character backed up over.

   <control>-V
       Synopsis:

	      <control>-V

	      <control>-Q

       Allow  the entry of any subsequent character, other than <control>-J or
       the <newline>, as a literal character,  removing	 any  special  meaning
       that  it may have to the editor in text input mode. If a <control>-V or
       <control>-Q is entered before a <control>-J  or	<newline>,  the	 <con‐
       trol>-V	or  <control>-Q	 character  shall  be discarded, and the <con‐
       trol>-J or <newline> shall behave as described in the <newline> command
       character during input mode.

       For  purposes  of the display only, the editor shall behave as if a '^'
       character was entered, and the cursor shall be positioned as  if	 over‐
       writing	the '^' character. When a subsequent character is entered, the
       editor shall behave as if that character was  entered  instead  of  the
       original <control>-V or <control>-Q character.

       Current line: Unchanged.

       Current column: Unchanged.

   <control>-W
       Synopsis:

	      <control>-W

       If there are characters other than autoindent characters that have been
       input on the current line before the cursor, the cursor shall move back
       over the last word preceding the cursor (including any <blank>s between
       the end of the last word and the current cursor); the cursor shall  not
       move  to	 before	 the  first  character after the end of any autoindent
       characters.

       Otherwise, if there are	autoindent  characters	on  the	 current  line
       before the cursor, it is implementation-defined whether the <control>-W
       command is an error or if the cursor moves to the first column position
       on the line.

       Otherwise, if the cursor is in column position 1 and there are previous
       lines that have been input, it is  implementation-defined  whether  the
       <control>-W  command  is	 an  error  or if it is equivalent to entering
       <control>-W after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All of the glyphs on columns between the starting cursor	 position  and
       (inclusively)  the ending cursor position shall become erase-columns as
       described in Input Mode Commands in vi .

       Current line: Unchanged, unless previously input lines are  erased,  in
       which case it shall be set to line -1.

       Current	column:	 Set  to the first column that displays any portion of
       the last character backed up over.

   <ESC>
       Synopsis:

	      <ESC>

       If input was part of a line-oriented command:

	1. If interrupt was entered, text input mode shall be  terminated  and
	   the	editor	shall  return  to  command mode. The terminal shall be
	   alerted.

	2. If <ESC> was entered, text input mode shall be terminated  and  the
	   command shall continue execution with the input provided.

       Otherwise, terminate text input mode and return to command mode.

       Any  autoindent	characters entered on newly created lines that have no
       other non- <newline>s shall be deleted.

       Any leading autoindent and <blank>s on newly  created  lines  shall  be
       rewritten to be the minimum number of <blank>s possible.

       The  screen  shall be redisplayed as necessary to match the contents of
       the edit buffer.

       Current line: Unchanged.

       Current column:

	1. If there are text input characters on the current line, the	column
	   shall  be set to the last column where any portion of the last text
	   input character is displayed.

	2. Otherwise, if a character  is  displayed  in	 the  current  column,
	   unchanged.

	3. Otherwise, set to column position 1.

EXIT STATUS
       The following exit values shall be returned:

	0     Successful completion.

       >0     An error occurred.

CONSEQUENCES OF ERRORS
       When  any error is encountered and the standard input is not a terminal
       device file, vi shall not write the file or return to command  or  text
       input mode, and shall terminate with a non-zero exit status.

       Otherwise,  when	 an  unrecoverable  error  is  encountered it shall be
       equivalent to a SIGHUP asynchronous event.

       Otherwise, when an error is encountered, the  editor  shall  behave  as
       specified in Command Descriptions in vi .

       The following sections are informative.

APPLICATION USAGE
       None.

EXAMPLES
       None.

RATIONALE
       See  the RATIONALE for ex for more information on vi. Major portions of
       the vi utility specification point to ex to  avoid  inadvertent	diver‐
       gence.  While  ex and vi have historically been implemented as a single
       utility, this is not required by IEEE Std 1003.1-2001.

       It is recognized that portions of vi would be difficult, if not	impos‐
       sible,  to implement satisfactorily on a block-mode terminal, or a ter‐
       minal without any form of cursor addressing, thus it is not a mandatory
       requirement  that such features should work on all terminals. It is the
       intention, however, that a vi implementation should  provide  the  full
       set of capabilities on all terminals capable of supporting them.

       Historically,  vi  exited  immediately  if the standard input was not a
       terminal. IEEE Std 1003.1-2001 permits,	but  does  not	require,  this
       behavior.  An end-of-file condition is not equivalent to an end-of-file
       character. A common end-of-file character, <control>-D, is historically
       a vi command.

       The  text  in the STDOUT section reflects the usage of the verb display
       in this section; some implementations of	 vi  use  standard  output  to
       write  to  the terminal, but IEEE Std 1003.1-2001 does not require that
       to be the case.

       Historically, implementations reverted to open mode if the terminal was
       incapable   of	supporting  full  visual  mode.	  IEEE Std 1003.1-2001
       requires this behavior. Historically,  the  open	 mode  of  vi  behaved
       roughly equivalently to the visual mode, with the exception that only a
       single line from the edit buffer (one "buffer line") was	 kept  current
       at any time.  This line was normally displayed on the next-to-last line
       of a terminal with cursor addressing (and the last line	performed  its
       normal  visual  functions for line-oriented commands and messages).  In
       addition, some few commands behaved differently in open	mode  than  in
       visual  mode.  IEEE Std 1003.1-2001  requires conformance to historical
       practice.

       Historically, ex and vi implementations have expected text  to  proceed
       in  the	usual  European/Latin  order  of left to right, top to bottom.
       There is no requirement in IEEE Std 1003.1-2001 that this be the	 case.
       The  specification  was deliberately written using words like "before",
       "after", "first", and "last" in order to permit implementations to sup‐
       port the natural text order of the language.

       Historically,  lines  past  the end of the edit buffer were marked with
       single tilde ( '~' ) characters; that is, if the one-based display  was
       20 lines in length, and the last line of the file was on line one, then
       lines 2-20 would contain only a single '~' character.

       Historically, the vi editor attempted to display only complete lines at
       the  bottom  of	the screen (it did display partial lines at the top of
       the screen). If a line was too long to fit in its entirety at the  bot‐
       tom of the screen, the screen lines where the line would have been dis‐
       played were displayed as single '@' characters, instead	of  displaying
       part  of the line.  IEEE Std 1003.1-2001 permits, but does not require,
       this behavior.  Implementations are encouraged  to  attempt  always  to
       display	a  complete  line  at  the  bottom  of	the  screen when doing
       scrolling or screen positioning by buffer lines.

       Historically, lines marked with '@' were also used to  minimize	output
       to dumb terminals over slow lines; that is, changes local to the cursor
       were updated, but changes to lines on the screen that were not close to
       the cursor were simply marked with an '@' sign instead of being updated
       to match the current text. IEEE Std 1003.1-2001 permits, but  does  not
       require	this feature because it is used ever less frequently as termi‐
       nals become smarter and connections are faster.

   Initialization in ex and vi
       Historically, vi always had a line in the edit buffer, even if the edit
       buffer was "empty". For example:

	1. The	ex command = executed from visual mode wrote "1" when the buf‐
	   fer was empty.

	2. Writes from visual mode of an empty edit buffer wrote  files	 of  a
	   single  character  (a  <newline>),  while writes from ex mode of an
	   empty edit buffer wrote empty files.

	3. Put and read commands into an empty edit buffer left an empty  line
	   at the top of the edit buffer.

       For  consistency,  IEEE Std 1003.1-2001	does  not  permit any of these
       behaviors.

       Historically, vi did not always return the  terminal  to	 its  original
       modes;  for  example,  ICRNL was modified if it was not originally set.
       IEEE Std 1003.1-2001 does not permit this behavior.

   Command Descriptions in vi
       Motion commands are  among  the	most  complicated  aspects  of	vi  to
       describe.  With some exceptions, the text region and buffer type effect
       of a motion command on a vi command are	described  on  a  case-by-case
       basis. The descriptions of text regions in IEEE Std 1003.1-2001 are not
       intended to imply direction; that is, an inclusive region from  line  n
       to  line	 n+5 is identical to a region from line n+5 to line n. This is
       of more than academic interest-movements to  marks  can	be  in	either
       direction,  and,	 if  the  wrapscan  option is set, so can movements to
       search points. Historically, lines are always stored  into  buffers  in
       text  order;  that  is,	from  the start of the edit buffer to the end.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

       Historically, command counts were applied to any associated motion, and
       were  multiplicative  to any supplied motion count. For example, 2cw is
       the same as c2w, and 2c3w is  the  same	as  c6w.  IEEE Std 1003.1-2001
       requires	 this  behavior. Historically, vi commands that used bigwords,
       words, paragraphs, and sentences as objects  treated  groups  of	 empty
       lines,  or  lines  that	contained only <blank>s, inconsistently.  Some
       commands treated them as a single entity,  while	 others	 treated  each
       line  separately.  For example, the w, W, and B commands treated groups
       of empty lines as individual words; that is, the command would move the
       cursor  to  each new empty line. The e and E commands treated groups of
       empty lines as a single word; that is, the first use  would  move  past
       the  group  of  lines. The b command would just beep at the user, or if
       done from the start of the line as a motion command, fail in unexpected
       ways. If the lines contained only (or ended with) <blank>s, the w and W
       commands would just beep at the user, the E and e commands would	 treat
       the  group  as  a single word, and the B and b commands would treat the
       lines as individual words. For consistency and simplicity of specifica‐
       tion,  IEEE Std 1003.1-2001  requires that all vi commands treat groups
       of empty or blank lines as a single entity, and that  movement  through
       lines ending with <blank>s be consistent with other movements.

       Historically,  vi  documentation	 indicated  that  any number of double
       quotes were skipped after punctuation  marks  at	 sentence  boundaries;
       however,	    implementations	only	 skipped     single    quotes.
       IEEE Std 1003.1-2001 requires both to be skipped.

       Historically, the first and last characters in  the  edit  buffer  were
       word    boundaries.   This   historical	 practice   is	 required   by
       IEEE Std 1003.1-2001.

       Historically, vi attempted to update the minimum number of  columns  on
       the  screen  possible, which could lead to misleading information being
       displayed. IEEE Std 1003.1-2001 makes no requirements other  than  that
       the current character being entered is displayed correctly, leaving all
       other decisions in this area up to the implementation.

       Historically, lines were arbitrarily  folded  between  columns  of  any
       characters  that required multiple column positions on the screen, with
       the exception of tabs,  which  terminated  at  the  right-hand  margin.
       IEEE Std 1003.1-2001 permits the former and requires the latter. Imple‐
       mentations that do not arbitrarily break lines between columns of char‐
       acters that occupy multiple column positions should not permit the cur‐
       sor to rest on a column that does not contain any part of a character.

       The historical vi had a problem in that all movements  were  by	buffer
       lines, not by display or screen lines. This is often the right thing to
       do; for example, single line movements, such as j or k, should work  on
       buffer  lines.  Commands	 like  dj, or j., where . is a change command,
       only make sense for buffer lines. It is not, however, the  right	 thing
       to  do  for screen motion or scrolling commands like <control>-D, <con‐
       trol>-F, and H. If the window is fairly small, using  buffer  lines  in
       these  cases  can  result  in  completely random motion; for example, 1
       <control>-D can result in a  completely	changed	 screen,  without  any
       overlap.	 This is clearly not what the user wanted. The problem is even
       worse in the case of the H, L, and M commands-as they position the cur‐
       sor  at	the  first non- <blank> of the line, they may all refer to the
       same location in large lines, and will result in no movement at all.

       In addition, if the line is larger than the screen, using buffer	 lines
       can  make  it impossible to display parts of the line-there are not any
       commands that do not display the beginning of the  line	in  historical
       vi,  and	 if  both  the	beginning and end of the line cannot be on the
       screen at the same time, the user suffers.  Finally, the page and half-
       page scrolling commands historically moved to the first non- <blank> in
       the new line. If the line is approximately the same size as the screen,
       this  is	 inadequate  because the cursor before and after a <control>-D
       command will refer to the same location on the screen.

       Implementations of ex and vi exist that	do  not	 have  these  problems
       because	the relevant commands ( <control>-B, <control>-D, <control>-F,
       <control>-U, <control>-Y, <control>-E, H, L, and M) operate on  display
       (screen) lines, not (edit) buffer lines.

       IEEE Std 1003.1-2001  does  not permit this behavior by default because
       the standard developers believed that users would find it  too  confus‐
       ing. However, historical practice has been relaxed. For example, ex and
       vi historically attempted, albeit sometimes  unsuccessfully,  to	 never
       put  part  of  a	 line on the last lines of a screen; for example, if a
       line would not fit in its entirety, no part of the line was  displayed,
       and  the	 screen	 lines	corresponding to the line contained single '@'
       characters.  This  behavior  is	permitted,   but   not	 required   by
       IEEE Std 1003.1-2001,  so  that	it  is possible for implementations to
       support long lines in small screens more	 reasonably  without  changing
       the  commands to be oriented to the display (instead of oriented to the
       buffer).	 IEEE Std 1003.1-2001 also permits implementations  to	refuse
       to  edit	 any  edit  buffer  containing a line that will not fit on the
       screen in its entirety.

       The display area (for example, the value of the window edit option) has
       historically  been "grown", or expanded, to display new text when local
       movements are done in displays where the number of lines	 displayed  is
       less  than  the	maximum possible.  Expansion has historically been the
       first choice, when the target line is less than	the  maximum  possible
       expansion value away.  Scrolling has historically been the next choice,
       done when the target line is less than half a display away, and	other‐
       wise,  the  screen was redrawn. There were exceptions, however, in that
       ex  commands  generally	always	caused	the  screen  to	 be   redrawn.
       IEEE Std 1003.1-2001 does not specify a standard behavior because there
       may be external issues, such as connection speed, the number of charac‐
       ters necessary to redraw as opposed to scroll, or terminal capabilities
       that implementations will have to accommodate.

       The current line in IEEE Std 1003.1-2001 maps one-to-one	 to  a	buffer
       line in the file. The current column does not.  There are two different
       column values that are described by IEEE Std 1003.1-2001.  The first is
       the  current column value as set by many of the vi commands. This value
       is remembered for the lifetime of the editor. The second	 column	 value
       is  the	actual	position on the screen where the cursor rests. The two
       are not always the same. For example, when the cursor is	 backed	 by  a
       multi-column  character,	 the  actual cursor position on the screen has
       historically been the last column of the character in command mode, and
       the first column of the character in input mode.

       Commands	 that  set  the	 current line, but that do not set the current
       cursor value (for example, j and k) attempt to get as close as possible
       to the remembered column position, so that the cursor tends to restrict
       itself to a vertical column as the user moves around in the  edit  buf‐
       fer.  IEEE Std 1003.1-2001 requires conformance to historical practice,
       requiring that the display location of the cursor on the	 display  line
       be  adjusted from the current column value as necessary to support this
       historical behavior.

       Historically, only a single line (and for some terminals, a single line
       minus  1	 column)  of  characters  could be entered by the user for the
       line-oriented commands; that is, :, !, /,  or  ?.  IEEE Std 1003.1-2001
       permits, but does not require, this limitation.

       Historically,  "soft"  errors  in vi caused the terminal to be alerted,
       but no error message was displayed. As a general rule, no error message
       was  displayed  for  errors  in command execution in vi, when the error
       resulted from the user attempting an invalid or impossible  action,  or
       when  a	searched-for  object  was  not	found. Examples of soft errors
       included h at the left margin, <control>-B or [[ at  the	 beginning  of
       the  file,  2G  at  the end of the file, and so on. In addition, errors
       such as %, ]], }, ), N, n, f, F, t, and T failing to find the searched-
       for  object  were soft as well. Less consistently, / and ? displayed an
       error message if the pattern was not found, /, ?, N, and n displayed an
       error message if no previous regular expression had been specified, and
       ; did not display an error message if no previous f, F, t, or T command
       had  occurred. Also, behavior in this area might reasonably be based on
       a runtime evaluation of the speed of a  network	connection.   Finally,
       some  implementations  have  provided error messages for soft errors in
       order to assist naive users, based on  the  value  of  a	 verbose  edit
       option. IEEE Std 1003.1-2001 does not list specific errors for which an
       error message shall be displayed.  Implementations  should  conform  to
       historical practice in the absence of any strong reason to diverge.

   Page Backwards
       The  <control>-B and <control>-F commands historically considered it an
       error to attempt to page past the beginning or end of the file, whereas
       the  <control>-D and <control>-U commands simply moved to the beginning
       or end of the file.  For consistency, IEEE Std 1003.1-2001 requires the
       latter behavior for all four commands. All four commands still consider
       it an error if the current line is  at  the  beginning  (  <control>-B,
       <control>-U)  or	 end ( <control>-F, <control>-D) of the file. Histori‐
       cally, the <control>-B and <control>-F commands skip two lines in order
       to  include  overlapping	 lines	when a single command is entered. This
       makes less sense in the presence of a count, as there will be, by defi‐
       nition, no overlapping lines. The actual calculation used by historical
       implementations of the vi editor for <control>-B was:

	      ((current first line) - count x (window edit option)) +2

       and for <control>-F was:

	      ((current first line) + count x (window edit option)) -2

       This calculation does not work well when intermixing commands with  and
       without	counts; for example, 3 <control>-F is not equivalent to enter‐
       ing the <control>-F command three  times,  and  is  not	reversible  by
       entering	 the  <control>-B  command  three  times. For consistency with
       other vi commands that take  counts,  IEEE Std 1003.1-2001  requires  a
       different calculation.

   Scroll Forward
       The  4BSD  and  System  V implementations of vi differed on the initial
       value used by the scroll command. 4BSD used:

	      ((window edit option) +1) /2

       while System V used the value of the scroll edit option. The  System  V
       version	is  specified  by  IEEE Std 1003.1-2001	 because  the standard
       developers believed that it was more intuitive and permitted the user a
       method  of  setting the scroll value initially without also setting the
       number of lines that are displayed.

   Scroll Forward by Line
       Historically, the <control>-E and <control>-Y commands considered it an
       error  if  the  last and first lines, respectively, were already on the
       screen. IEEE Std 1003.1-2001 requires conformance to  historical	 prac‐
       tice.  Historically,  the  <control>-E  and <control>-Y commands had no
       effect in open mode.  For simplicity and consistency of	specification,
       IEEE Std 1003.1-2001  requires that they behave as usual, albeit with a
       single line screen.

   Clear and Redisplay
       The historical <control>-L command refreshed the screen exactly	as  it
       was  supposed  to  be currently displayed, replacing any '@' characters
       for lines that had been deleted but not	updated	 on  the  screen  with
       refreshed  '@' characters.  The intent of the <control>-L command is to
       refresh when the screen has been accidentally overwritten; for example,
       by a write command from another user, or modem noise.

   Redraw Screen
       The  historical	<control>-R command redisplayed only when necessary to
       update lines that had been deleted but not updated on  the  screen  and
       that were flagged with '@' characters. There is no requirement that the
       screen be in any way refreshed if no lines of this form	are  currently
       displayed.  IEEE Std 1003.1-2001 permits implementations to extend this
       command to refresh lines on the	screen	flagged	 with  '@'  characters
       because	they  are  too	long to be displayed in the current framework;
       however, the current line and column need not be modified.

   Search for tagstring
       Historically, the first non- <blank> at or after	 the  cursor  was  the
       first  character,  and all subsequent characters that were word charac‐
       ters, up to the end of the line, were included. For example,  with  the
       cursor  on  the	leading	 space	or  on	the  '#' character in the text
       "#bar@", the tag was "#bar" . On the character 'b' it was "bar", and on
       the 'a' it was "ar" . IEEE Std 1003.1-2001 requires this behavior.

   Replace Text with Results from Shell Command
       Historically,  the  <, >, and ! commands considered most cursor motions
       other than line-oriented motions an error;  for	example,  the  command
       >/foo<CR>  succeeded, while the command >l failed, even though the text
       region described by the two commands might be identical.	  For  consis‐
       tency,  all  three  commands only consider entire lines and not partial
       lines, and the region is defined as any line that contains a  character
       that was specified by the motion.

   Move to Matching Character
       Other  matching	characters  have  been	left implementation-defined in
       order to allow extensions such as matching '<' and  '>'	for  searching
       HTML, or #ifdef, #else, and #endif for searching C source.

   Repeat Substitution
       IEEE Std 1003.1-2001  requires  that any c and g flags specified to the
       previous substitute command be ignored; however, the r flag  may	 still
       apply, if supported by the implementation.

   Return to Previous (Context or Section)
       The [[, ]], (, ), {, and } commands are all affected by "section bound‐
       aries", but in some historical implementations not all of the  commands
       recognize  the  same  section boundaries. This is a bug, not a feature,
       and a unique section-boundary algorithm was not described for each com‐
       mand.   One special case that is preserved is that the sentence command
       moves to the end of the last line of the edit buffer  while  the	 other
       commands	 go  to	 the  beginning,  in order to preserve the traditional
       character cut semantics of the sentence command. Historically, vi  sec‐
       tion  boundaries	 at  the beginning and end of the edit buffer were the
       first non- <blank> on the first and last lines of the  edit  buffer  if
       one  exists;  otherwise, the last character of the first and last lines
       of the edit buffer if one exists.  To increase consistency  with	 other
       section	locations, this has been simplified by IEEE Std 1003.1-2001 to
       the first character of the first and last lines of the edit buffer,  or
       the first and the last lines of the edit buffer if they are empty.

       Sentence	 boundaries  were  problematic in the historical vi. They were
       not only the boundaries as defined for the section and  paragraph  com‐
       mands,  but  they were the first non- <blank> that occurred after those
       boundaries, as well. Historically, the vi section commands  were	 docu‐
       mented  as taking an optional window size as a count preceding the com‐
       mand.  This  was	  not	implemented   in   historical	versions,   so
       IEEE Std 1003.1-2001  requires  that  the count repeat the command, for
       consistency with other vi commands.

   Repeat
       Historically, mapped commands other than text input commands could  not
       be  repeated  using  the period command.	 IEEE Std 1003.1-2001 requires
       conformance to historical practice.

       The restrictions on the interpretation of special characters (for exam‐
       ple,  <control>-H)  in  the  repetition	of text input mode commands is
       intended to match historical practice. For  example,  given  the	 input
       sequence:

	      iab<control>-H<control>-H<control>-Hdef<escape>

       the  user  should  be  informed	of an error when the sequence is first
       entered, but not during a command repetition. The character <control>-T
       is  specifically exempted from this restriction. Historical implementa‐
       tions of vi ignored <control>-T characters that were input in the orig‐
       inal  command during command repetition. IEEE Std 1003.1-2001 prohibits
       this behavior.

   Find Regular Expression
       Historically, commands did not affect the line searched to or  from  if
       the  motion  command  was a search ( /, ?, N, n) and the final position
       was the start/end of the line. There were some special cases and vi was
       not consistent. IEEE Std 1003.1-2001 does not permit this behavior, for
       consistency. Historical implementations permitted but  were  unable  to
       handle  searches	 as  motion commands that wrapped (that is, due to the
       edit option wrapscan) to the  original  location.  IEEE Std 1003.1-2001
       requires that this behavior be treated as an error.

       Historically,  the  syntax "/RE/0" was used to force the command to cut
       text in line mode. IEEE Std 1003.1-2001 requires conformance to histor‐
       ical practice.

       Historically,  in  open	mode, a z specified to a search command redis‐
       played the current line instead of displaying the current  screen  with
       the  current line highlighted. For consistency and simplicity of speci‐
       fication, IEEE Std 1003.1-2001 does not permit this behavior.

       Historically, trailing z commands were permitted and ignored if entered
       as  part of a search used as a motion command. For consistency and sim‐
       plicity of specification, IEEE Std 1003.1-2001  does  not  permit  this
       behavior.

   Execute an ex Command
       Historically,  vi implementations restricted the commands that could be
       entered on the colon command line (for example, append and change), and
       some  other commands were known to cause them to fail catastrophically.
       For consistency, IEEE Std 1003.1-2001 does not  permit  these  restric‐
       tions.  When  executing an ex command by entering :, it is not possible
       to enter a <newline> as part of the command because  it	is  considered
       the  end	 of  the  command. A different approach is to enter ex command
       mode by using the vi Q command (and later resuming visual mode with the
       ex vi command). In ex command mode, the single-line limitation does not
       exist. So, for example, the following is valid:

	      Q
	      s/break here/break\
	      here/
	      vi

       IEEE Std 1003.1-2001 requires that, if the ex  command  overwrites  any
       part  of	 the screen that would be erased by a refresh, vi pauses for a
       character from the user. Historically,  this  character	could  be  any
       character;  for	example, a character input by the user before the mes‐
       sage appeared, or even a mapped character. This is probably a bug,  but
       implementations	that  have tried to be more rigorous by requiring that
       the user enter a specific character, or that the user enter a character
       after  the  message was displayed, have been forced by user indignation
       back into historical behavior.  IEEE Std 1003.1-2001  requires  confor‐
       mance to historical practice.

   Shift Left (Right)
       Refer  to  the  Rationale for the ! and / commands. Historically, the <
       and > commands sometimes moved the cursor to  the  first	 non-  <blank>
       (for  example  if the command was repeated or with _ as the motion com‐
       mand), and sometimes left it unchanged. IEEE Std 1003.1-2001  does  not
       permit  this  inconsistency,  requiring	instead that the cursor always
       move to the first non- <blank>. Historically, the < and > commands  did
       not  support  buffer arguments, although some implementations allow the
       specification of an optional buffer. This behavior is neither  required
       nor disallowed by IEEE Std 1003.1-2001.

   Execute
       Historically,  buffers could execute other buffers, and loops, infinite
       and otherwise, were possible.   IEEE Std 1003.1-2001  requires  confor‐
       mance  to  historical  practice.	  The  *  buffer  syntax  of ex is not
       required in vi, because it is not historical practice and has been used
       in some vi implementations to support additional scripting languages.

   Reverse Case
       Historically,  the  ~  command  ignored any associated count, and acted
       only on the characters in the current line. For consistency with	 other
       vi commands, IEEE Std 1003.1-2001 requires that an associated count act
       on the next count characters, and that the command move	to  subsequent
       lines if warranted by count, to make it possible to modify large pieces
       of text in a reasonably efficient manner. There	exist  vi  implementa‐
       tions  that  optionally	require an associated motion command for the ~
       command. Implementations supporting this functionality  are  encouraged
       to  base it on the tildedop edit option and handle the text regions and
       cursor positioning identically to the yank command.

   Append
       Historically, counts specified to the A, a, I, and i commands  repeated
       the  input of the first line count times, and did not repeat the subse‐
       quent lines of the input text. IEEE Std 1003.1-2001 requires  that  the
       entire text input be repeated count times.

   Move Backward to Preceding Word
       Historically,  vi  became confused if word commands were used as motion
       commands in empty files.	 IEEE Std 1003.1-2001 requires that this be an
       error.  Historical  implementations of vi had a large number of bugs in
       the word movement commands, and they varied greatly in behavior in  the
       presence	 of  empty  lines,  "words" made up of a single character, and
       lines containing only <blank>s. For consistency and simplicity of spec‐
       ification, IEEE Std 1003.1-2001 does not permit this behavior.

   Change to End-of-Line
       Some  historical	 implementations  of  the  C command did not behave as
       described by IEEE Std 1003.1-2001 when the $ key was  remapped  because
       they  were  implemented	by  pushing the $ key onto the input queue and
       reprocessing it.	 IEEE Std 1003.1-2001 does not permit  this  behavior.
       Historically,  the C, S, and s commands did not copy replaced text into
       the numeric buffers. For consistency and simplicity  of	specification,
       IEEE Std 1003.1-2001  requires that they behave like their respective c
       commands in all respects.

   Delete
       Historically, lines in open mode that were deleted  were	 scrolled  up,
       and  an	@ glyph written over the beginning of the line. In the case of
       terminals that are incapable of the necessary cursor motions, the  edi‐
       tor  erased  the	 deleted  line	from  the screen. IEEE Std 1003.1-2001
       requires conformance to historical practice; that is, if	 the  terminal
       cannot display the '@' character, the line cannot remain on the screen.

   Delete to End-of-Line
       Some  historical	 implementations  of  the  D command did not behave as
       described by IEEE Std 1003.1-2001 when the $ key was  remapped  because
       they  were  implemented	by  pushing the $ key onto the input queue and
       reprocessing it.	 IEEE Std 1003.1-2001 does not permit this behavior.

   Join
       An historical oddity of vi is that the commands J, 1J, and 2J  are  all
       equivalent.   IEEE Std 1003.1-2001  requires  conformance to historical
       practice.  The vi J command is specified in terms of the ex  join  com‐
       mand with an ex command count value. The address correction for a count
       that is past the end of the edit buffer	is  necessary  for  historical
       compatibility for both ex and vi.

   Mark Position
       Historical  practice  is	 that only lowercase letters, plus '`' and '",
       could be used to mark a cursor position. IEEE Std 1003.1-2001  requires
       conformance  to	historical practice, but encourages implementations to
       support other characters as marks as well.

   Repeat Regular Expression Find (Forward and Reverse)
       Historically, the N and n commands could not be used as	motion	compo‐
       nents  for  the	c command. With the exception of the cN command, which
       worked if the search crossed a line boundary, the text region would  be
       discarded,  and	the  user would not be in text input mode. For consis‐
       tency and simplicity of specification,  IEEE Std 1003.1-2001  does  not
       permit this behavior.

   Insert Empty Line (Below and Above)
       Historically, counts to the O and o commands were used as the number of
       physical lines to open, if the  terminal	 was  dumb  and	 the  slowopen
       option  was  not	 set.  This was intended to minimize traffic over slow
       connections and repainting  for	dumb  terminals.  IEEE Std 1003.1-2001
       does  not permit this behavior, requiring that a count to the open com‐
       mand behave as for other text input commands. This change to historical
       practice	 was made for consistency, and because a superset of the func‐
       tionality is provided by the slowopen edit option.

   Put from Buffer (Following and Before)
       Historically, counts to the p and P commands were ignored if the buffer
       was  a  line mode buffer, but were (mostly) implemented as described in
       IEEE Std 1003.1-2001 if the buffer was a character mode buffer. Because
       implementations	exist  that  do	 not have this limitation, and because
       pasting lines multiple times is generally useful,  IEEE Std 1003.1-2001
       requires that count be supported for all p and P commands.

       Historical  implementations of vi were widely known to have major prob‐
       lems in the p and P commands, particularly when unusual regions of text
       were  copied into the edit buffer. The standard developers viewed these
       as bugs, and they are not permitted for consistency and	simplicity  of
       specification.

       Historically, a P or p command (or an ex put command executed from open
       or visual mode) executed in an empty file, left an empty	 line  as  the
       first  line  of	the file. For consistency and simplicity of specifica‐
       tion, IEEE Std 1003.1-2001 does not permit this behavior.

   Replace Character
       Historically, the r command did not correctly handle the erase and word
       erase  characters  as  arguments, nor did it handle an associated count
       greater than 1 with a <carriage-return> argument, for which it replaced
       count characters with a single <newline>. IEEE Std 1003.1-2001 does not
       permit these inconsistencies.

       Historically, the r  command  permitted	the  <control>-V  escaping  of
       entered	characters,  such as <ESC> and the <carriage-return>; however,
       it  required  two  leading  <control>-V	characters  instead  of	  one.
       IEEE Std 1003.1-2001 requires that this be changed for consistency with
       the other text input commands of vi.

       Historically, it is an error to enter the r command if there  are  less
       than  count characters at or after the cursor in the line. While a rea‐
       sonable and unambiguous extension would be to permit the r  command  on
       empty  lines,  it  would	 require that too large a count be adjusted to
       match the number of characters at or after the cursor for  consistency,
       which is sufficiently different from historical practice to be avoided.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

   Replace Characters
       Historically, if there were autoindent characters in the line on	 which
       the  R  command	was  run,  and autoindent was set, the first <newline>
       would be properly indented and no characters would be replaced  by  the
       <newline>.  Each additional <newline> would replace n characters, where
       n was the number of characters that were needed to indent the  rest  of
       the line to the proper indentation level. This behavior is a bug and is
       not permitted by IEEE Std 1003.1-2001.

   Undo
       Historical practice for cursor positioning after undoing	 commands  was
       mixed.  In  most	 cases,	 when  undoing commands that affected a single
       line, the cursor was moved to the start of added or  changed  text,  or
       immediately after deleted text. However, if the user had moved from the
       line being changed, the	column	was  either  set  to  the  first  non-
       <blank>,	 returned to the origin of the command, or remained unchanged.
       When undoing commands that affected multiple lines or entire lines, the
       cursor  was moved to the first character in the first line restored. As
       an example of how inconsistent this was, a search,  followed  by	 an  o
       text  input command, followed by an undo would return the cursor to the
       location where the o command was entered, but a cw command followed  by
       an  o  command followed by an undo would return the cursor to the first
       non- <blank> of the line. IEEE Std 1003.1-2001 requires the most useful
       of  these  behaviors, and discards the least useful, in the interest of
       consistency and simplicity of specification.

   Yank
       Historically, the yank command did not move to the end of the motion if
       the  motion  was	 in  the forward direction. It moved to the end of the
       motion if the motion was in the backward direction, except  for	the  _
       command,	 or for the G and ' commands when the end of the motion was on
       the current line.  This was further complicated by the fact that for  a
       number  of  motion  commands, the yank command moved the cursor but did
       not update the screen; for example, a subsequent command would move the
       cursor from the end of the motion, even though the cursor on the screen
       had  not	 reflected  the	 cursor	 movement  for	 the   yank   command.
       IEEE Std 1003.1-2001  requires  that  all yank commands associated with
       backward motions move the cursor to the end of the motion  for  consis‐
       tency,  and specifically, to make ' commands as motions consistent with
       search patterns as motions.

   Yank Current Line
       Some historical implementations of the Y	 command  did  not  behave  as
       described by IEEE Std 1003.1-2001 when the '_' key was remapped because
       they were implemented by pushing the '_' key onto the input  queue  and
       reprocessing it. IEEE Std 1003.1-2001 does not permit this behavior.

   Redraw Window
       Historically, the z command always redrew the screen. This is permitted
       but not required by IEEE Std 1003.1-2001, because of the	 frequent  use
       of  the	z  command in macros such as map n nz. for screen positioning,
       instead of its use to change the screen size. The  standard  developers
       believed that expanding or scrolling the screen offered a better inter‐
       face for users. The ability to redraw the screen is  preserved  if  the
       optional new window size is specified, and in the <control>-L and <con‐
       trol>-R commands.

       The semantics of z^ are confusing at best. Historical practice is  that
       the screen before the screen that ended with the specified line is dis‐
       played. IEEE Std 1003.1-2001 requires conformance to  historical	 prac‐
       tice.

       Historically, the z command would not display a partial line at the top
       or bottom of the screen. If the partial line would normally  have  been
       displayed at the bottom of the screen, the command worked, but the par‐
       tial line was replaced with '@' characters. If the partial  line	 would
       normally	 have  been  displayed	at  the top of the screen, the command
       would  fail.   For  consistency	and   simplicity   of	specification,
       IEEE Std 1003.1-2001 does not permit this behavior.

       Historically,  the z command with a line specification of 1 ignored the
       command.	  For	consistency   and   simplicity	  of	specification,
       IEEE Std 1003.1-2001 does not permit this behavior.

       Historically,  the z command did not set the cursor column to the first
       non- <blank> for the character if the first screen was to be displayed,
       and was already displayed. For consistency and simplicity of specifica‐
       tion, IEEE Std 1003.1-2001 does not permit this behavior.

   Input Mode Commands in vi
       Historical implementations of vi did not permit the user to erase  more
       than  a single line of input, or to use normal erase characters such as
       line erase, worderase, and erase to  erase  autoindent  characters.  As
       there  exist  implementations of vi that do not have these limitations,
       both behaviors are permitted, but only historical practice is required.
       In the case of these extensions, vi is required to pause at the autoin‐
       dent and previous line boundaries.

       Historical implementations of vi updated only the portion of the screen
       where  the  current  cursor character was displayed.  For example, con‐
       sider the vi input keystrokes:

	      iabcd<escape>0C<tab>

       Historically, the <tab> would overwrite the characters "abcd"  when  it
       was  displayed.	Other  implementations	replace only the 'a' character
       with the <tab>, and then push the rest of the characters ahead  of  the
       cursor.	Both implementations have problems. The historical implementa‐
       tion is probably visually nicer for the above example; however, for the
       keystrokes:

	      iabcd<ESC>0R<tab><ESC>

       the  historical implementation results in the string "bcd" disappearing
       and then magically reappearing when the	<ESC>  character  is  entered.
       IEEE Std 1003.1-2001  requires  the  former  behavior  when overwriting
       erase-columns-that is, overwriting characters that are no longer	 logi‐
       cally part of the edit buffer-and the latter behavior otherwise.

       Historical  implementations  of	vi discarded the <control>-D and <con‐
       trol>-T characters when they were entered at places where their command
       functionality  was  not appropriate. IEEE Std 1003.1-2001 requires that
       the <control>-T functionality always be available, and that <control>-D
       be  treated  as	any other key when not operating on autoindent charac‐
       ters.

   NUL
       Some historical implementations of vi limited the number of  characters
       entered	  using	   the	  NUL	 input	 character   to	  256	bytes.
       IEEE Std 1003.1-2001 permits this limitation; however,  implementations
       are encouraged to remove this limit.

   <control>-D
       See  also  Rationale  for  the input mode command <newline>. The hidden
       assumptions in the <control>-D command (and in the vi autoindent speci‐
       fication	 in  general)  is that <space>s take up a single column on the
       screen and that <tab>s are comprised of an integral number of <space>s.

   <newline>
       Implementations are permitted to rewrite autoindent characters  in  the
       line  when  <newline>,  <carriage-return>, <control>-D, and <control>-T
       are entered, or when the shift commands are  used,  because  historical
       implementations have both done so and found it necessary to do so.  For
       example, a <control>-D when the cursor is preceded by a	single	<tab>,
       with  tabstop  set  to  8,  and shiftwidth set to 3, will result in the
       <tab> being replaced by several <space>s.

   <control>-T
       See also the Rationale for the input mode command  <newline>.  Histori‐
       cally,  <control>-T  only worked if no non- <blank>s had yet been input
       in the current input line. In  addition,	 the  characters  inserted  by
       <control>-T  were  treated  as  autoindent characters, and could not be
       erased using normal  user  erase	 characters.  Because  implementations
       exist  that  do	not  have these limitations, and as moving to a column
       boundary is generally useful, IEEE Std 1003.1-2001 requires  that  both
       limitations be removed.

   <control>-V
       Historically,  vi  used ^V, regardless of the value of the literal-next
       character of the terminal.  IEEE Std 1003.1-2001	 requires  conformance
       to historical practice.

       The  uses described for <control>-V can also be accomplished with <con‐
       trol>-Q, which is useful on terminals  that  use	 <control>-V  for  the
       down-arrow function. However, most historical implementations use <con‐
       trol>-Q for the termios START character, so the editor  will  generally
       not  receive  the  <control>-Q unless stty ixon mode is set to off. (In
       addition, some historical implementations of  vi	 explicitly  set  ixon
       mode  to on, so it was difficult for the user to set it to off.) Any of
       the command characters described in IEEE Std 1003.1-2001	 can  be  made
       ineffective by their selection as termios control characters, using the
       stty utility or other methods described in the System Interfaces volume
       of IEEE Std 1003.1-2001.

   <ESC>
       Historically,  SIGINT alerted the terminal when used to end input mode.
       This behavior is permitted, but not required, by IEEE Std 1003.1-2001.

FUTURE DIRECTIONS
       None.

SEE ALSO
       ed, ex, stty

COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the	referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003				VI(1P)
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