indent(1)indent(1)NAMEindent - changes the appearance of a C program by inserting or deleting
whitespace
SYNOPSISindent [-bad] [-bap] [-bbb] [-bc] [-bl] [-bliN] [-br] [-cN] [-cdN]
[-cdb] [-ce] [-ciN] [-cliN] [-cpN] [-cs] [-bs] [-dN] [-diN] [-fc1]
[-fca] [-gnu] [-iN] [-ipN] [-kr] [-lN] [-lp] [-nbad] [-nbap] [-nbbb]
[-nbc] [-ncdb] [-nce] [-ncs] [-nfc1] [-nfca] [-nip] [-nlp] [-npcs]
[-npsl] [-nsc] [-nsob] [-nss] [-nv] [-orig] [-npro] [-pcs] [-psl] [-sc]
[-sob] [-ss] [-st] [-T] [-tsN] [-v] [-version] [file]
OPTIONS
Here is a list of all the options for indent, alphabetized by short
option. It is followed by a cross key alphabetized by long option.
Force blank lines after the declarations.
Long option: --blank-lines-after-declarations Force blank lines
after procedure bodies.
Long option: --blank-lines-after-procedures Force blank lines
after block comments.
Long option: --blank-lines-after-block-comments Force newline
after comma in declaration.
Long option: --blank-lines-after-commas Put braces on line after
if, etc.
Long option: --braces-after-if-line Indent braces N spaces.
Long option: --brace-indentN Put braces on line with if, etc.
Long option:--braces-on-if-line Put comments to the right of
code in column N.
Long option: --comment-indentationN Put comments to the right of
the declarations in column N.
Long option: --declaration-comment-columnN Put comment delim‐
iters on blank lines.
Long option: --comment-delimiters-on-blank-lines Cuddle else and
preceding }.
Long option: --cuddle-else Continuation indent of N spaces.
Long option: --continuation-indentationN Case label indent of N
spaces.
Long option: --case-indentationN Put comments to the right of
#else and #endif statements in column N.
Long option: --else-endif-columnN Put a space after a cast oper‐
ator.
Long option: --space-after-cast Put a space between sizeof and
its argument.
Long option: --blank-before-sizeof Set indentation of comments
not to the right of code to N spaces.
Long option: --line-comments-indentationN Put variables in col‐
umn N.
Long option: --declaration-indentationN Format comments in the
first column.
Long option: --format-first-column-comments Do not disable all
formatting of comments.
Long option: --format-all-comments Use GNU coding style. This
is the default.
Long option: --gnu-style Set indentation level to N spaces.
Long option: --indent-levelN Indent parameter types in old-style
function definitions by N spaces.
Long option: --parameter-indentationN Use Kernighan & Ritchie
coding style.
Long option: --k-and-r-style Set maximum line length to N.
Long option: --line-lengthN Line up continued lines at parenthe‐
ses.
Long option: --continue-at-parentheses Do not force blank lines
after declarations.
Long option: --no-blank-lines-after-declarations Do not force
blank lines after procedure bodies.
Long option: --no-blank-lines-after-procedures Do not force
blank-lines after block comments.
Long option: --no-blank-lines-after-block-comments Do not force
newlines after commas in declarations.
Long option: --no-blank-lines-after-commas Do not put comment
delimiters on blank lines.
Long option: --no-comment-delimiters-on-blank-lines Do not cud‐
dle } and else.
Long option: --dont-cuddle-else Do not put a space after cast
operators.
Long option: --no-space-after-casts Do not format comments in
the first column as normal.
Long option: --dont-format-first-column-comments Do not format
any comments.
Long option: --dont-format-comments Zero width indentation for
parameters.
Long option: --no-parameter-indentation Do not line up parenthe‐
ses.
Long option: --dont-line-up-parentheses Do not put space after
the function in function calls.
Long option: --no-space-after-function-call-names Put the type
of a procedure on the same line as its name.
Long option: --dont-break-procedure-type Do not put the * char‐
acter at the left of comments.
Long option: --dont-star-comments Do not swallow optional blank
lines.
Long option: --leave-optional-blank-lines Do not force a space
before the semicolon after certain statements. Disables -ss.
Long option: --dont-space-special-semicolon Long option: --no-
verbosity Use the original Berkeley coding style.
Long option: --original Do not read files.
Long option: --ignore-profile Insert a space between the name of
the procedure being called and the (.
Long option: --space-after-procedure-calls Put the type of a
procedure on the line before its name.
Long option: --procnames-start-lines Put the * character at the
left of comments.
Long option: --start-left-side-of-comments Swallow optional
blank lines.
Long option: --swallow-optional-blank-lines On one-line for and
while statements, force a blank before the semicolon.
Long option: --space-special-semicolon Write to standard output.
Long option: --standard-output Tell indent the name of type‐
names. Set tab size to N spaces.
Long option: --tab-sizeN Enable verbose mode.
Long option: --verbose Output the version number of indent.
OPTIONS CROSS-REFERENCE
Here is a list of options alphabetized by long option to help you find
the corresponding short option.
--blank-lines-after-block-comments-bbb
--blank-lines-after-commas-bc
--blank-lines-after-declarations-bad
--blank-lines-after-procedures-bap
--braces-after-if-line-bl
--brace-indent-bli
--braces-on-if-line-br
--case-indentation-cliN
--comment-delimiters-on-blank-lines-cdb
--comment-indentation-cN
--continuation-indentation-ciN
--continue-at-parentheses-lp
--cuddle-else-ce
--declaration-comment-column-cdN
--declaration-indentation-diN
--dont-break-procedure-type-npsl
--dont-cuddle-else-nce
--dont-format-comments-nfca
--dont-format-first-column-comments-nfc1
--dont-line-up-parentheses-nlp
--dont-space-special-semicolon-nss
--dont-star-comments-nsc
--else-endif-column-cpN
--format-all-comments-fca
--format-first-column-comments-fc1
--gnu-style-gnu
--ignore-profile-npro
--indent-level-iN
--k-and-r-style-kr
--leave-optional-blank-lines-nsob
--line-comments-indentation-dN
--line-length-lN
--no-blank-lines-after-block-comments-nbbb
--no-blank-lines-after-commas-nbc
--no-blank-lines-after-declarations-nbad
--no-blank-lines-after-procedures-nbap
--no-comment-delimiters-on-blank-lines-ncdb
--no-space-after-casts-ncs
--no-parameter-indentation-nip
--no-space-after-function-call-names-npcs
--no-verbosity-nv
--original-orig
--parameter-indentation-ipN
--procnames-start-lines-psl
--space-after-cast-cs
--space-after-procedure-calls-pcs
--space-special-semicolon-ss
--standard-output-st
--start-left-side-of-comments-sc
--swallow-optional-blank-lines-sob
--tab-size-tsN
--verbose-v
DESCRIPTION
This man page is based on the Info file indent.info, produced by Make‐
info-1.47 from the input file indent.texinfo. This is Edition 0.02, 5
May 1992, of The indent Manual (for indent Version 1.3).
Copyright (C) 1989, 1992 Free Software Foundation, Inc.
COPYING
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
INTRODUCTION
The indent program can be used to make code easier to read. It can
also convert from one style of writing C to another.
The indent program understands a substantial amount about the syntax of
C, but it also attempts to cope with incomplete and misformed syntax.
In version 1.2 and more recent versions, the GNU style of indenting is
the default.
INVOKING INDENT
As of version 1.3, the format of the indent command is:
indent [OPTIONS] [INPUT-FILES] indent [OPTIONS] [SINGLE-INPUT-FILE] [-o
OUTPUT-FILE]
This format is different from earlier versions and other versions of
indent.
In the first form, one or more input files are specified. The indent
program makes a backup copy of each file, and the original file is
replaced with its indented version. For an explanation of how backups
are made, see Backup Files.
In the second form, only one input file is specified. In this case, or
when the standard input is used, you may specify an output file after
the -o option.
To cause indent to write to standard output, use the -st option. This
is only allowed when there is only one input file, or when the standard
input is used.
If no input files are named, the standard input is read for input.
Also, if a filename named - is specified, then the standard input is
read.
As an example, each of the following commands will input the program
slithy_toves.c and write its indented text to slithy_toves.out:
indent slithy_toves.c -o slithy_toves.out indent-st slithy_toves.c >
slithy_toves.out cat slithy_toves.c | indent-o slithy_toves.out
Most other options to indent control how programs are formatted. As of
version 1.2, indent also recognizes a long name for each option name.
Long options are prefixed by either -- or +. The + prefix is being
superseded by -- to maintain consistency with the POSIX standard. In
most of this document, the traditional, short names are used for the
sake of brevity.
As another example, the following command will indent the program
test/metabolism.c using the -br and -l85 options, write the output back
to test/metabolism.c, and write the original contents of test/metabo‐
lism.c to a backup file in the directory test:
indent-br test/metabolism.c -l85
Equivalent invocations using long option names for this example would
be:
indent--braces-on-if-line--line-length185 test/metabolism.c indent
+braces-on-if-line +line-length185 test/metabolism.c
If you find that you often use indent with the same options, you may
put those options into a file named indent program will first look for
in the current directory and use that file if it is found. Otherwise,
indent will search your home directory for and use that file if it is
found. This behavior is different from that of other versions of
indent, which load both files if they both exist.
Command line switches are handled *after* processing with one excep‐
tion: Explicitly specified options always override background options
(see COMMON STYLES). You can prevent indent from reading an file by
specifying the -npro option.
BACKUP FILES
As of version 1.3, GNU indent makes GNU-style backup files, the same
way GNU Emacs does. This means that either “simple” or “numbered”
backup filenames may be made.
Simple backup file names are generated by appending a suffix to the
original file name. The default for the this suffix is the one-charac‐
ter string ~ (tilde). Thus, the backup file for python.c would be
python.c~.
Instead of the default, you may specify any string as a suffix by set‐
ting the environment variable SIMPLE_BACKUP_SUFFIX to your preferred
suffix.
Numbered backup versions of a file momewraths look like
momewraths.c.~23~, where 23 is the version of this particular backup.
When making a numbered backup of the file src/momewrath.c, the backup
file will be named src/momewrath.c.~V~, where V is one greater than the
highest version currently existing in the directory src.
The type of backup file made is controlled by the value of the environ‐
ment variable VERSION_CONTROL. If it is the string simple, then only
simple backups will be made. If its value is the string numbered, then
numbered backups will be made. If its value is numbered-existing, then
numbered backups will be made if numbered backups *already exist* for
the file being indented; otherwise, a simple backup is made. If VER‐
SION_CONTROL is not set, then indent assumes the behavior of numbered-
existing.
Other versions of indent use the suffix in naming backup files. This
behavior can be emulated by setting SIMPLE_BACKUP_SUFFIX to
Note also that other versions of indent make backups in the current
directory, rather than in the directory of the source file as GNU
indent now does.
COMMON STYLES
Common styles of C code include the GNU style, the Kernighan & Ritchie
style, and the original Berkeley style. A style may be selected with a
single “background” option, which specifies a set of values for all
other options. However, explicitly specified options always override
options implied by a background option.
As of version 1.2, the default style of GNU indent is the GNU style.
Thus, it is no longer necessary to specify the option -gnu to obtain
this format, although doing so will not cause an error. Option set‐
tings which correspond to the GNU style are:
-nbad-bap-nbbb -nbc -bl -bli2 -c33 -cd33 -ncdb -nce -cli0 -cp1 -di0
-nfc1 -nfca -i2 -ip5 -lp -pcs -psl -nsc -nsob -nss -ts8
The GNU coding style is the style that is preferred by the GNU project.
It is the style that the GNU Emacs C mode encourages and which is used
in the C portions of GNU Emacs. (People interested in writing programs
for Project GNU should get a copy of The GNU Coding Standards, which
also covers semantic and portability issues such as memory usage, the
size of integers, etc.)
The Kernighan & Ritchie style is used throughout their well-known book
The C Programming Language. It is enabled with the -kr option. The
Kernighan & Ritchie style corresponds to the following set of options:
-nbad-bap-nbbb-nbc-br -c33 -cd33 -ncdb -ce -ci4 -cli0 -cp33 -d0
-di1 -nfc1 -nfca -i4 -ip0 -l75 -lp -npcs -npsl -nsc -nsob -nss -ts8
Kernighan & Ritchie style does not put comments to the right of code in
the same column at all times (nor does it use only one space to the
right of the code), so for this style indent has arbitrarily chosen
column 33.
The style of the original Berkeley indent may be obtained by specifying
-orig (or by specifying --original, the long option name). This style
is equivalent to the following settings: -nbap -nbad -nbbb -bc -br -c33
-cd33 -cdb -ce -ci4 -cli0 -cp33 -d4 -di16 -fc1 -fca -i4 -ip4 -l75-lp
-npcs -psl -sc -nsob -nss -ts8
BLANK LINES
Various programming styles use blank lines in different places. The
indent program has a number of options to insert or delete blank lines
in specific places.
The -bad option causes indent to force a blank line after every block
of declarations. The -nbad option causes indent not to force such
blank lines.
The -bap option forces a blank line after every procedure body. The
-nbap option forces no such blank line.
The -bbb option forces a blank line before every block comment. A block
comment is one which starts in column one when formatting of such com‐
ments is disabled, or one with - or * immediately following the /*. The
-nbbb option does not force such blank lines.
The -sob option causes indent to swallow optional blank lines (that is,
any optional blank lines present in the input will be removed from the
output). If the -nsob is specified, any blank lines present in the
input file will be copied to the output file.
The -bad option forces a blank line after every block of declarations.
The -nbad option does not add any such blank lines.
For example, given the input:
char *foo;
char *bar;
/* This separates blocks of declarations. */
int baz;
The -bad option produces:
char *foo;
char *bar;
/* This separates blocks of declarations. */
int baz;
The -nbad option produces:
char *foo;
char *bar;
/* This separates blocks of declarations. */
int baz;
The -bap option forces a blank line after every procedure body. For
example, given the input:
int
foo ()
{
puts("Hi");
}
/* The procedure bar is even less interesting. */
char *
bar ()
{
puts("Hello");
}
The -bap option produces:
int
foo ()
{
puts ("Hi");
}
/* The procedure bar is even less interesting. */
char *
bar ()
{
puts ("Hello");
}
The -nbap option produces:
int
foo ()
{
puts ("Hi");
}
/* The procedure bar is even less interesting. */
char *
bar ()
{
puts ("Hello");
}
No blank line will be added after the procedure foo.
COMMENTS
Comments are no longer formatted by default as of version 1.2. This can
be enabled with the -fca option. Doing so will cause newlines in the
comment text to be ignored and the line will be filled up to the length
of a line (which can be modified with -l). When formatting is enabled,
blank lines indicate paragraph breaks.
The -fc1 option enables the formatting of comments which begin in the
first column. The -nfc1 option disables the formatting of first column
comments. When comment formatting is disabled, overall comment inden‐
tation may still be adjusted.
The indentation of comments which do not appear to the right of code is
set by the -d option, which specifies the number of spaces to the left
of the surrounding code that the comment appears. For example, -d2
places comments two spaces to the left of the code; -d0 lines up com‐
ments with the code. The -cdb option controls whether the /* and */ are
placed on blank lines. With -cdb, comments look like this:
/*
* this is a comment
*/
With -ncdb, comments look like this:
/* this is a comment */
The -cdb option affects only block comments, not comments to the right
of code. The default is -ncdb.
Comments that appear on the same line as code are placed to the right.
The column in which comments on code start is controlled by the -c
option. The column in which comments to the right of declarations
start is controlled by the -cd option. By default, they start in the
same column as comments to the right of code, which is column 33. The
column number for comments to the right of #else and #endif statements
is controlled by the -cp option. If the code on a line extends past
the comment column, the comment starts further to the right, and the
right margin may be automatically extended in extreme cases.
If the -sc option is specified, * is placed at the left edge of all
comments. For example:
/* This is a comment which extends from one line
* onto the next line, thus causing us to consider
* how it should continue. */
instead of:
/* This is a comment which extends from one line
onto the next line, thus causing us to consider
how it should continue. */
STATEMENTS
The -br or -bl option specifies how to format braces. The -br option
formats braces like this:
if (x > 0) {
x--;
}
The -bl option formats them like this:
if (x > 0)
{
x--;
}
If you use the -bl option, you may also want to specify the -bli
option. This option specifies the number of spaces by which braces are
indented. -bli2, the default, gives the result shown above. The -bli0
option results in the following:
if (x > 0)
{
x--;
}
If you are using the -br option, you probably want to also use the -ce
option. This causes the else in an if-then-else construct to cuddle up
to the immediately preceding }. For example, with -br -ce, you get the
following:
if (x > 0) {
x--;
} else { <!-- COMMENT follows --> fprintf (stderr, "...some‐
thing wrong?\n");
}
With -br -nce, that code would appear as follows:
if (x > 0) {
x--;
}
else { <!-- COMMENT follows --> fprintf (stderr, "...some‐
thing wrong?\n");
}
The -cli option specifies the number of spaces that case labels should
be indented to the right of the containing switch statement.
If a semicolon is on the same line as a for or while statement, the -ss
option will cause a space to be placed before the semicolon. This
emphasizes the semicolon, making it clear that the body of the for or
while statement is an empty statement. The -nss option disables this
feature.
The -pcs option causes a space to be placed between the name of the
procedure being called and the left parenthesis, for example, puts
("Hi");. The -npcs option would give puts("Hi");.
If the -cs option is specified, indent puts a space after a cast opera‐
tor.
The -bs option ensures that there is a space between the keyword sizeof
and its argument. In some versions, this is known as the Bill_Shannon
option.
DECLARATIONS
By default, indent will line up identifiers in the column specified by
the -di option. For example, -di16 makes things appear as follows:
int foo;
char *bar;
Using a small value (such as one or two) for the -di option can be used
to cause the identifiers to be placed in the first available position.
For example:
int foo;
char *bar;
The value given to the -di option will still affect variables that are
put on separate lines from their types; for example, -di2 will lead to:
int
foo;
If the -bc option is specified, a newline is forced after each comma in
a declaration. For example:
int a,
b,
c;
With the -nbc option, the preceding declaration would appear as fol‐
lows:
int a, b, c;
The -psl option causes the type of a procedure being defined to be
placed on the line before the name of the procedure. This style is
required for the etags program to work correctly, as well as some of
the c-mode functions of Emacs.
If you are not using the -di1 option to place variables being declared
immediately after their type, you need to use the -T option to tell
indent the name of all the typenames in your program that are defined
by typedef. The -T option can be specified more than once, and all
names specified are used. For example, you would use the options -T
CODE_ADDR -T COLOR if your program contains:
typedef unsigned long CODE_ADDR;
typedef enum {red, blue, green} COLOR;
INDENTATION
One issue in the formatting of code is how far each line should be
indented from the left margin. When the beginning of a statement such
as if or for is encountered, the indentation level is increased by the
value specified by the -i option. For example, use -i8 to specify an
eight-character indentation for each level. When a statement is contin‐
ued from a previous line, it is indented by a number of additional spa‐
ces specified by the -ci option. The -ci option defaults to 0. However,
if the -lp option is specified and a line has a left parenthesis that
is not closed on that line, then continuation lines will be lined up to
start at the character position just after the left parenthesis. This
processing also applies to [ and applies to { when it occurs in ini‐
tialization lists. For example, a piece of continued code might appear
as follows with -nlp -ci3 in effect:
p1 = first_procedure (second_procedure (p2, p3),
third_procedure (p4, p5));
With -lp in effect, the code is somewhat clearer:
p1 = first_procedure (second_procedure (p2, p3),
third_procedure (p4, p5));
The indent program assumes that tabs are placed at regular intervals of
both input and output character streams. These intervals are by default
8 columns wide, but (as of version 1.2) may be changed by the -ts
option. Tabs are treated as the equivalent number of spaces.
The indentation of type declarations in old-style function definitions
is controlled by the -ip parameter. This is a numeric parameter speci‐
fying how many spaces that type declarations are to be indented. For
example, the default -ip5 makes definitions look like this:
char *
create_world (x, y, scale)
int x;
int y;
float scale;
{
. . .
}
For compatibility with other versions of indent, the option -nip is
provided, which is equivalent to -ip0.
MISCELLANEOUS OPTIONS
To find out what version of indent you have, use the command indent-version. This will report the version number of indent, without doing
any of the normal processing.
The -v option can be used to turn on verbose mode. When in verbose
mode, indent reports when it splits one line of input into two more
lines of output, and gives some size statistics at completion.
COPYRIGHT
The following copyright notice applies to the indent program. The copy‐
right and copying permissions for this manual appear near the beginning
of this document.
Copyright (c) 1989, 1992 Free Software Foundation
Copyright (c) 1985 Sun Microsystems, Inc.
Copyright (c) 1980 The Regents of the University of California.
Copyright (c) 1976 Board of Trustees of the University of Illinois.
All rights reserved.
Redistribution and use in source and binary forms are permitted pro‐
vided that the above copyright notice and this paragraph are duplicated
in all such forms and that any documentation, advertising materials,
and other materials related to such distribution and use acknowledge
that the software was developed by the University of California, Berke‐
ley, the University of Illinois, Urbana, and Sun Microsystems, Inc.
The name of either University or Sun Microsystems may not be used to
endorse or promote products derived from this software without specific
prior written permission. THIS SOFTWARE IS PROVIDED “AS IS” AND WITHOUT
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE
IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PUR‐
POSE.
RETURN VALUE
Unknown
AUTHOR
The Free Software Foundation.
HISTORY
Derived from the UCB program “indent”.
FILES
Holds default options for the indent program.
indent(1)