pg(1)

pg -- file perusal filter for CRTs

Synopsis

pg [-number] [-p string] [-cefnrs] [+linenumber] [+/pattern/] [file . . .]

Description

The pg command is a filter that allows the examination of files one screenful at a time on a CRT. (If no file is specified or if it encounters the file name -, pg reads from standard input.) Each screenful is followed by a prompt. If the user types a carriage return, another page is displayed; other possibilities are listed below. pg processes supplementary code set characters in files, and recognizes supplementary code set characters in the string given to the -p option (see below) according to the locale specified in the LC_CTYPE environment variable (see LANG on environ(5)). In regular expressions, pattern searches are performed on characters, not bytes, as described on ed(1).

This command is different from previous paginators in that it allows you to back up and review something that has already passed. The method for doing this is explained below.

To determine terminal attributes, pg scans the terminfo data base for the terminal type specified by the environment variable TERM. If TERM is not defined, the terminal type dumb is assumed.

The command line options are:

-number: An integer specifying the size (in lines) of the window that pg is to use instead of the default. (On a terminal containing 24 lines, the default window size is 23).
-c: Home the cursor and clear the screen before displaying each page. This option is ignored if clear_screen is not defined for this terminal type in the terminfo data base.
-e: Causes pg not to pause at the end of each file.
-f: Normally, pg splits lines longer than the screen width at characters, but some sequences of characters in the text being displayed (for example, escape sequences for underlining) generate undesirable results. The -f option inhibits pg from splitting lines.
-n: Normally, commands must be terminated by a newline character. This option causes an automatic end of command as soon as a command letter is entered.
-p string: Causes pg to use string as the prompt. If the prompt string contains a %d, the first occurrence of %d in the prompt will be replaced by the current page number when the prompt is issued. The default prompt string is ``:''. string may contain supplementary code set characters.
-r: Restricted mode. The shell escape is disallowed. pg will print an error message but does not exit.
-s: Causes pg to print all messages and prompts in standout mode (usually inverse video).
+linenumber: Start up at linenumber. The display will begin at line n, ebven if the number of lines that remain in the file is less than what can be displayed on the screen.
+/pattern/: Start up at the first line containing the basic regular expression (BRE) pattern (see grep(1)).

The responses that may be typed when pg pauses can be divided into three categories: those causing further perusal, those that search, and those that modify the perusal environment.

Commands that cause further perusal normally take a preceding address, an optionally signed number indicating the point from which further text should be displayed. This address is interpreted in either pages or lines depending on the command. A signed address specifies a point relative to the current page or line, and an unsigned address specifies an address relative to the beginning of the file. Each command has a default address that is used if none is provided.

The perusal commands and their defaults are as follows:

(+1)<newline> or <blank>: This causes one page to be displayed. The address is specified in pages.
(+1) l: With a relative address this causes pg to simulate scrolling the screen, forward or backward, the number of lines specified. With an absolute address this command prints a screenful beginning at the specified line.
(+1) d or ^D: Simulates scrolling half a screen forward or backward.
if: Skip i screens of text.
iz: Same as newline except that i, if present, becomes the new default number of lines per screenful.

The following perusal commands take no address.

. or ^L: Typing a single period causes the current page of text to be redisplayed.
$: Displays the last windowful in the file. Use with caution when the input is a pipe.

The following commands are available for searching for text patterns in the text. The regular expressions described in ed(1) are available. They must always be terminated by a newline, even if the -n option is specified.

i/pattern/: Search forward for the ith (default i=1) occurrence of the BRE pattern. Searching begins immediately after the current page and continues to the end of the current file, without wrap-around.
i^pattern^ or i?pattern?: Search backwards for the ith (default i=1) occurrence of the BRE pattern. Searching begins immediately before the current page and continues to the beginning of the current file, without wrap-around. The ``^'' notation is useful for Adds 100 terminals which will not properly handle the ``?''.

After searching, pg will normally display the line found at the top of the screen. This can be modified by appending m or b to the search command to leave the line found in the middle or at the bottom of the window from now on. The suffix t can be used to restore the original situation.

The user of pg can modify the environment of perusal with the following commands:

in: Begin perusing the ith next file in the command line. The i is an unsigned number, default value is 1.
ip: Begin perusing the ith previous file in the command line. i is an unsigned number, default is 1.
iw: Display another window of text. If i is present, set the window size to i.
s filename: Save the input in the named file. Only the current file being perused is saved. The white space between the s and filename is optional. This command must always be terminated by a newline, even if the -n option is specified.
h: Help by displaying an abbreviated summary of available commands.
q or Q: Quit pg.
!command: Command is passed to the shell, whose name is taken from the SHELL environment variable. If this is not available, the default shell is used. This command must always be terminated by a newline, even if the -n option is specified.

At any time when output is being sent to the terminal, the user can press the quit key (normally <Ctrl>-\) or the interrupt (break) key. This causes pg to stop sending output, and display the prompt. The user may then enter one of the above commands in the normal manner. Unfortunately, some output is lost when this is done, because any characters waiting in the terminal's output queue are flushed when the quit signal occurs.

If the standard output is not a terminal, then pg acts just like cat except that a header is printed before each file (if there is more than one).

Files

/usr/share/lib/terminfo/?/: terminal information database
/tmp/pg*: temporary file when input is from a pipe If $TMPDIR is defined in the user's environment, use TMPDIR for temporary space rather than /tmp.
/usr/lib/locale/locale/LC_MESSAGES/uxcore.abi: language-specific message file (See LANG on environ(5).)

Examples

The following command line uses pg to read the system news:

news | pg -p "(Page %d):"

References

ed(1), grep(1), more(1), terminfo(4)

Notices

While waiting for terminal input, pg responds to BREAK, <Del>, and <Ctrl>-\ by terminating execution. Between prompts, however, these signals interrupt pg's current task and place the user in prompt mode. These should be used with caution when input is being read from a pipe, since an interrupt is likely to terminate the other commands in the pipeline.

The terminal /, ^, or ? may be omitted from the searching commands.

If terminal tabs are not set every eight positions, undesirable results may occur.

When using pg as a filter with another command that changes the terminal I/O options, terminal settings may not be restored correctly.