INDENT(1) INDENT(1)
NAME
indent - changes the appearance of a C program by inserting or
deleting whitespace.
SYNOPSIS
indent [options] [input-files]
indent [options] [single-input-file] [-o output-file]
indent --version
DESCRIPTION
This man page is generated from the file indent.texinfo. This is
Edition of "The indent Manual", for Indent Version , last updated .
The indent program can be used to make code easier to read. It can
also convert from one style of writing C to another.
indent understands a substantial amount about 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.
OPTIONS
-as, --align-with-spaces
If using tabs for indentation, use spaces for alignment.
See INDENTATION.
-bad, --blank-lines-after-declarations
Force blank lines after the declarations.
See BLANK LINES.
-bap, --blank-lines-after-procedures
Force blank lines after procedure bodies.
See BLANK LINES.
-bbb, --blank-lines-before-block-comments
Force blank lines before block comments.
See BLANK LINES.
-bbo, --break-before-boolean-operator
Prefer to break long lines before boolean operators.
See BREAKING LONG LINES.
-bc, --blank-lines-after-commas
Force newline after comma in declaration.
See DECLARATIONS.
-bl, --braces-after-if-line
Put braces on line after if, etc.
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See STATEMENTS.
-blf, --braces-after-func-def-line
Put braces on line following function definition line.
See DECLARATIONS.
-blin, --brace-indentn
Indent braces n spaces.
See STATEMENTS.
-bls, --braces-after-struct-decl-line
Put braces on the line after struct declaration lines.
See DECLARATIONS.
-br, --braces-on-if-line
Put braces on line with if, etc.
See STATEMENTS.
-brf, --braces-on-func-def-line
Put braces on function definition line.
See DECLARATIONS.
-brs, --braces-on-struct-decl-line
Put braces on struct declaration line.
See DECLARATIONS.
-bs, --Bill-Shannon, --blank-before-sizeof
Put a space between sizeof and its argument.
See STATEMENTS.
-cn, --comment-indentationn
Put comments to the right of code in column n.
See COMMENTS.
-cbin, --case-brace-indentationn
Indent braces after a case label N spaces.
See STATEMENTS.
-cdn, --declaration-comment-columnn
Put comments to the right of the declarations in column n.
See COMMENTS.
-cdb, --comment-delimiters-on-blank-lines
Put comment delimiters on blank lines.
See COMMENTS.
-cdw, --cuddle-do-while
Cuddle while of do {} while; and preceding }.
See COMMENTS.
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-ce, --cuddle-else
Cuddle else and preceding }.
See COMMENTS.
-cin, --continuation-indentationn
Continuation indent of n spaces.
See STATEMENTS.
-clin, --case-indentationn
Case label indent of n spaces.
See STATEMENTS.
-cpn, --else-endif-columnn
Put comments to the right of #else and #endif statements in column
n.
See COMMENTS.
-cs, --space-after-cast
Put a space after a cast operator.
See STATEMENTS.
-dn, --line-comments-indentationn
Set indentation of comments not to the right of code to n spaces.
See COMMENTS.
-bfda, --break-function-decl-args
Break the line before all arguments in a declaration.
See DECLARATIONS.
-bfde, --break-function-decl-args-end
Break the line after the last argument in a declaration.
See DECLARATIONS.
-dj, --left-justify-declarations
If -cd 0 is used then comments after declarations are left
justified behind the declaration.
See DECLARATIONS.
-din, --declaration-indentationn
Put variables in column n.
See DECLARATIONS.
-fc1, --format-first-column-comments
Format comments in the first column.
See COMMENTS.
-fca, --format-all-comments
Do not disable all formatting of comments.
See COMMENTS.
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-fnc, --fix-nested-comments
Fix nested comments.
See COMMENTS.
-gnu, --gnu-style
Use GNU coding style. This is the default.
See COMMON STYLES.
-gts, --gettext-strings
Treat gettext _("...") and N_("...") as strings rather than as
functions.
See BREAKING LONG LINES.
-hnl, --honour-newlines
Prefer to break long lines at the position of newlines in the
input.
See BREAKING LONG LINES.
-in, --indent-leveln
Set indentation level to n spaces.
See INDENTATION.
-iln, --indent-labeln
Set offset for labels to column n.
See INDENTATION.
-ipn, --parameter-indentationn
Indent parameter types in old-style function definitions by n
spaces.
See INDENTATION.
-kr, --k-and-r-style
Use Kernighan & Ritchie coding style.
See COMMON STYLES.
-ln, --line-lengthn
Set maximum line length for non-comment lines to n.
See BREAKING LONG LINES.
-lcn, --comment-line-lengthn
Set maximum line length for comment formatting to n.
See COMMENTS.
-linux, --linux-style
Use Linux coding style.
See COMMON STYLES.
-lp, --continue-at-parentheses
Line up continued lines at parentheses.
See INDENTATION.
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-lps, --leave-preprocessor-space
Leave space between # and preprocessor directive.
See INDENTATION.
-nlps, --remove-preprocessor-space
Remove space between # and preprocessor directive.
See INDENTATION.
-nbad, --no-blank-lines-after-declarations
Do not force blank lines after declarations.
See BLANK LINES.
-nbap, --no-blank-lines-after-procedures
Do not force blank lines after procedure bodies.
See BLANK LINES.
-nbbo, --break-after-boolean-operator
Do not prefer to break long lines before boolean operators.
See BREAKING LONG LINES.
-nbc, --no-blank-lines-after-commas
Do not force newlines after commas in declarations.
See DECLARATIONS.
-nbfda, --dont-break-function-decl-args
Dont put each argument in a function declaration on a separate
line.
See DECLARATIONS.
-ncdb, --no-comment-delimiters-on-blank-lines
Do not put comment delimiters on blank lines.
See COMMENTS.
-ncdw, --dont-cuddle-do-while
Do not cuddle } and the while of a do {} while;.
See STATEMENTS.
-nce, --dont-cuddle-else
Do not cuddle } and else.
See STATEMENTS.
-ncs, --no-space-after-casts
Do not put a space after cast operators.
See STATEMENTS.
-ndjn, --dont-left-justify-declarations
Comments after declarations are treated the same as comments after
other statements.
See DECLARATIONS.
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-nfc1, --dont-format-first-column-comments
Do not format comments in the first column as normal.
See COMMENTS.
-nfca, --dont-format-comments
Do not format any comments.
See COMMENTS.
-ngts, --no-gettext-strings
Treat gettext _("...") and N_("...") as normal functions. This is
the default.
See BREAKING LONG LINES.
-nhnl, --ignore-newlines
Do not prefer to break long lines at the position of newlines in
the input.
See BREAKING LONG LINES.
-nip, --no-parameter-indentation
Zero width indentation for parameters.
See INDENTATION.
-nlp, --dont-line-up-parentheses
Do not line up parentheses.
See STATEMENTS.
-npcs, --no-space-after-function-call-names
Do not put space after the function in function calls.
See STATEMENTS.
-nprs, --no-space-after-parentheses
Do not put a space after every ( and before every ).
See STATEMENTS.
-npsl, --dont-break-procedure-type
Put the type of a procedure on the same line as its name.
See DECLARATIONS.
-nsaf, --no-space-after-for
Do not put a space after every for.
See STATEMENTS.
-nsai, --no-space-after-if
Do not put a space after every if.
See STATEMENTS.
-nsaw, --no-space-after-while
Do not put a space after every while.
See STATEMENTS.
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-nsc, --dont-star-comments
Do not put the * character at the left of comments.
See COMMENTS.
-nsob, --leave-optional-blank-lines
Do not swallow optional blank lines.
See BLANK LINES.
-nss, --dont-space-special-semicolon
Do not force a space before the semicolon after certain
statements. Disables -ss.
See STATEMENTS.
-ntac, --dont-tab-align-comments
Do not pad comments out to the nearest tabstop.
See COMMENTS.
-nut, --no-tabs
Use spaces instead of tabs.
See INDENTATION.
-nv, --no-verbosity
Disable verbose mode.
See MISCELLANEOUS OPTIONS.
-orig, --original
Use the original Berkeley coding style.
See COMMON STYLES.
-npro, --ignore-profile
Do not read .indent.pro files.
See INVOKING INDENT.
-pal, --pointer-align-left
Put asterisks in pointer declarations on the left of spaces, next
to types: char* p.
-par, --pointer-align-right
Put asterisks in pointer declarations on the right of spaces, next
to variable names: char *p. This is the default behavior.
-pcs, --space-after-procedure-calls
Insert a space between the name of the procedure being called and
the (.
See STATEMENTS.
-pin, --paren-indentationn
Specify the extra indentation per open parentheses ( when a
statement is broken.See STATEMENTS.
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-pmt, --preserve-mtime
Preserve access and modification times on output files.See
MISCELLANEOUS OPTIONS.
-ppin, --preprocessor-indentationn
Specify the indentation for preprocessor conditional
statements.See INDENTATION.
-prs, --space-after-parentheses
Put a space after every ( and before every ).
See STATEMENTS.
-psl, --procnames-start-lines
Put the type of a procedure on the line before its name.
See DECLARATIONS.
-saf, --space-after-for
Put a space after each for.
See STATEMENTS.
-sai, --space-after-if
Put a space after each if.
See STATEMENTS.
-sar, --spaces-around-initializers
Put a space after the { and before the } in initializers.
See DECLARATIONS.
-saw, --space-after-while
Put a space after each while.
See STATEMENTS.
-sbin, --struct-brace-indentationn
Indent braces of a struct, union or enum N spaces.
See STATEMENTS.
-sc, --start-left-side-of-comments
Put the * character at the left of comments.
See COMMENTS.
-slc, --single-line-conditionals
Allow for unbraced conditionals (if, else, etc.) to have their
inner statement on the same line.
See STATEMENTS.
-sob, --swallow-optional-blank-lines
Swallow optional blank lines.
See BLANK LINES.
-ss, --space-special-semicolon
On one-line for and while statements, force a blank before the
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semicolon.
See STATEMENTS.
-st, --standard-output
Write to standard output.
See INVOKING INDENT.
-T Tell indent the name of typenames.
See DECLARATIONS.
-tsn, --tab-sizen
Set tab size to n spaces.
See INDENTATION.
-ut, --use-tabs
Use tabs. This is the default.
See INDENTATION.
-v, --verbose
Enable verbose mode.
See MISCELLANEOUS OPTIONS.
-version
Output the version number of indent.
See MISCELLANEOUS OPTIONS.
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. indent
makes a backup copy of each file, and the original file is replaced
with its indented version. See BACKUP FILES, for an explanation of
how backups are made.
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.
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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 +. [ + 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. See OPTION SUMMARY, for a list of options,
including both long and short names.
Here is another example:
indent -br test/metabolism.c -l85
This 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/metabolism.c to a backup file in the
directory test.
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.pro. indent will look for
a profile the environment variable INDENT_PROFILE. If that exists its
value is expected to name the file that is to be used. If the
environment variable does not exist, indent looks for .indent.pro in
the current directory
and use that if found. Finally indent will search your home
directory for .indent.pro and use that file if it is found. This
behaviour is different from that of other versions of indent, which
load both files if
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The format of .indent.pro is simply a list of options, just as they
would appear on the command line, separated by white space (tabs,
spaces, and newlines). Options in .indent.pro may be surrounded by C
or C++ comments, in which case they are ignored.
Command line switches are handled after processing
.indent.pro. Options specified later override arguments specified
earlier, with one exception: Explicitly specified options always
override background options (See COMMON STYLES). You can prevent
indent from reading an .indent.pro 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 this suffix is the one-character
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
setting the environment variable SIMPLE_BACKUP_SUFFIX to your
preferred suffix.
Numbered backup versions of a file momeraths.c look like
momeraths.c.~23~, where 23 is the version of this particular backup.
When making a numbered backup of the file src/momeraths.c, the backup
file will be named src/momeraths.c.~V~, where V is one greater than
the the directory src. The environment variable VERSION_WIDTH
controls the number of digits, using left zero padding when necessary.
For instance, setting this variable to "2" will lead to the backup
file being named momeraths.c.~04~.
The type of backup file made is controlled by the value of the
environment 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 there already
exist numbered backups for the file being indented; otherwise, a
simple backup is made. If VERSION_CONTROL is not set, then indent
assumes the behaviour of numbered-existing.
Other versions of indent use the suffix .BAK in naming backup files.
This behaviour can be emulated by setting SIMPLE_BACKUP_SUFFIX to
.BAK.
Note also that other versions of indent make backups in the current
directory, rather than in the directory of the source file as GNU
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indent now does.
COMMON STYLES
There are several common styles of C code, including 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
settings which correspond to the GNU style are:
-nbad -bap -nbc -bbo -bl -bli2 -bls -ncdb -nce -cp1 -cs -di2
-ndj -nfc1 -nfca -hnl -i2 -ip5 -lp -pcs -nprs -psl -saf -sai
-saw -nsc -nsob
The GNU coding style is that 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 -bbo -nbc -br -brs -c33 -cd33 -ncdb -ce -ci4 -cli0
-cp33 -cs -d0 -di1 -nfc1 -nfca -hnl -i4 -ip0 -l75 -lp -npcs
-nprs -npsl -saf -sai -saw -nsc -nsob -nss -par
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, using the long option
name). This style is equivalent to the following settings:
-nbad -nbap -bbo -bc -br -brs -c33 -cd33 -cdb -ce -ci4 -cli0
-cp33 -di16 -fc1 -fca -hnl -i4 -ip4 -l75 -lp -npcs -nprs -psl
-saf -sai -saw -sc -nsob -nss -ts8
The Linux style is used in the linux kernel code and drivers. Code
generally has to follow the Linux coding style to be accepted. This
style is equivalent to the following settings:
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-nbad -bap -nbc -bbo -hnl -br -brs -c33 -cd33 -ncdb -ce -ci4
-cli0 -d0 -di1 -nfc1 -i8 -ip0 -l80 -lp -npcs -nprs -npsl -sai
-saf -saw -ncs -nsc -sob -nfca -cp33 -ss -ts8 -il1
BLANK LINES
Various programming styles use blank lines in different places.
indent has a number of options 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
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 boxed comment (See
COMMENTS.) 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.
--blank-lines-after-declarations
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;
indent -bad produces
char *foo;
char *bar;
/* This separates blocks of declarations. */
int baz;
and indent -nbad produces
char *foo;
char *bar;
/* This separates blocks of declarations. */
int baz;
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--blank-lines-after-procedures
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");
}
indent -bap produces
int
foo ()
{
puts ("Hi");
}
/* The procedure bar is even less interesting. */
char *
bar ()
{
puts ("Hello");
}
and indent -nbap 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
indent formats both C and C++ /*, terminated with */ and may contain
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newline characters. C++ comments begin with the delimiter // and end
at the newline.
indent handles comments differently depending upon indent attempts to
distinguish between comments statements, comments which follow
declarations, comments following preprocessor directives, and comments
which are not preceded by code of any sort, i.e., they begin the text
of the line (although not necessarily in column 1).
indent further distinguishes between comments found procedures and
aggregates, and those found within them. In particular, comments
beginning a line found within a procedure will be indented to the
column at which code is currently indented. The exception to this is
a comment beginning in the leftmost column; such a comment is output
at that column.
indent attempts to leave boxed comments general idea of such a comment
is that it is enclosed in a rectangle or box of stars or dashes to
visually set it apart. More precisely, boxed comments are defined as
those in which the initial /* is followed immediately by the character
*, =, _, or -, or those in which the beginning comment delimiter (/*)
is on a line by itself, and the following line begins with a * in the
same column as the star of the opening delimiter.
Examples of boxed comments are:
/**********************
* Comment in a box!! *
**********************/
/*
* A different kind of scent,
* for a different kind of comment.
*/
indent attempts to leave boxed comments in the source file. Thus the
indentation of the comment is unchanged, and its length is not checked
in any way. The only alteration made is that an embedded tab
character may be converted into the appropriate number of spaces.
If the -bbb option is specified, all such boxed comments will be
preceded by a blank line, unless such a comment is preceded by code.
Comments which are not boxed comments may be formatted, which means
that the line is broken to fit within a right margin and left-filled
with whitespace. Single newlines are equivalent to a space, but blank
lines (two or more newlines in a row) are taken to mean a paragraph
break. Formatting of comments which begin after the first column is
enabled with the -fca option. To format those beginning in column
one, specify -fc1. Such formatting is disabled by default.
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The right margin for formatting defaults to 78, but may be changed
with the -lc option. If the margin specified does not allow the
comment to be printed, the margin will be automatically extended for
the duration of that comment. The margin is not respected if the
comment is not being formatted.
If the -fnc option is specified, all comments with /* embedded will
have that character sequence replaced by a space followed by the
character * thus eliminating nesting.
If the comment begins a line (i.e., there is no program text to its
left), it will be indented to the column it was found in unless the
comment is within a block of code. In that case, such a comment will
be aligned with the indented code of that block (unless the comment
began in the first column). This alignment may be affected by the -d
option, which specifies an amount by which such comments are moved to
the left, or unindented. For example, -d2 places comments two spaces
to the left of code. By default, comments are aligned with code,
unless they begin in the first column, in which case they are left
there by default --- to get them aligned with the code, specify -fc1.
Comments to the right of code will appear by default in column 33.
This may be changed with one of three options. -c will specify the
column for comments following code, -cd specifies the column for
comments following declarations, and -cp specifies the column for
comments following preprocessor directives #else and #endif. -dj
together with -cd0 can be used to suppress alignment of comments to
the right of declarations, causing the comment to follow one tabstop
from the end of the declaration. Normally -cd0 causes -c to become
effective.
If the code to the left of the comment exceeds the beginning column,
the comment column will be extended to the next tabstop column past
the end of the code, unless the -ntac option is specified. In the
case of preprocessor directives,comments are extended to to one space
past the end of the directive. This extension lasts only for the
output of that particular comment.
The -cdb option places the comment delimiters on blank lines. Thus, a
single line comment like /* Loving hug */ can be transformed into:
/*
Loving hug
*/
Stars can be placed at the beginning of multi-line comments with the
-sc option. Thus, the single-line comment above can be transformed
(with -cdb -sc) into:
/*
* Loving hug
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*/
STATEMENTS
The -br or -bl option specifies how to format braces.
The -br option formats statement 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. -
bli0 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 {
fprintf (stderr, "...something wrong?\n");
}
With -br -nce that code would appear as
if (x > 0) {
x--;
}
else {
fprintf (stderr, "...something wrong?\n");
}
An exception to the behavior occurs when there is a comment between
the right brace and the subsequent else statement. While the -br
- 17 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
option will cause a left brace to jump over the comment, the else does
not jump over the comment to cuddle because it has a strong likelihood
of changing the meaning of the comment.
The -cdw option causes the while in a do-while loop to cuddle up to
the immediately preceding }. For example, with -cdw you get the
following:
do {
x--;
} while (x);
With -ncdw that code would appear as
do {
x--;
}
while (x);
The -slc option allows for an unbraced conditional and its inner
statement to appear on the same line. For example:
if (x) x--;
else x++;
Without -slc that code would appear as
if (x)
x--;
else
x++;
The -cli option specifies the number of spaces that case labels should
be indented to the right of the containing switch statement.
The default gives code like:
switch (i)
{
case 0:
break;
case 1:
{
++i;
}
default:
break;
}
Using the -cli2 that would become:
- 18 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
switch (i)
{
case 0:
break;
case 1:
{
++i;
}
default:
break;
}
The indentation of the braces below a case statement can be controlled
with the -cbin option. For example, using -cli2 -cbi0 results in:
switch (i)
{
case 0:
break;
case 1:
{
++i;
}
default:
break;
}
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. -nss disables this feature.
The -pcs option causes a space to be placed between the name of the
procedure being called and the ( (for example, puts ("Hi");. The
-npcs option would give puts("Hi");).
If the -cs option is specified, indent puts a space between a cast
operator and the object to be cast. The -ncs ensures that there is no
space between the cast operator and the object. Remember that indent
only knows about the standard C data types and so cannot recognise
user-defined types in casts. Thus (mytype)thing is not treated as a
cast.
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.
The -saf option forces a space between a for and the following
parenthesis. This is the default.
- 19 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
The -sai option forces a space between a if and the following
parenthesis. This is the default.
The -saw option forces a space between a while and the following
parenthesis. This is the default.
The -prs option causes all parentheses to be separated with a space
from whatever is between them. For example, using -prs results in
code like:
while ( ( e_code - s_code ) < ( dec_ind - 1 ) )
{
set_buf_break ( bb_dec_ind );
*e_code++ = ;
}
DECLARATIONS
By default indent will line up identifiers, in the column specified by
the -di option. For example, -di16 makes things look like:
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 which
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 this would look like
int a, b, c;
The -bfda option causes a newline to be forced after the comma
separating the arguments of a function declaration. The arguments
- 20 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
will appear at one indention level deeper than the function
declaration. This is particularly helpful for functions with long
argument lists. The option -bfde causes a newline to be forced before
the closing bracket of the function declaration. For both options the
n setting is the default: -nbfda and -nbfde.
For example,
void foo (int arg1, char arg2, int *arg3, long arg4, char arg5);
With the -bfda option this would look like
void foo (
int arg1,
char arg2,
int *arg3,
long arg4,
char arg5);
With, in addition, the -bfde option this would look like
void foo (
int arg1,
char arg2,
int *arg3,
long arg4,
char arg5
);
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.
You must use the -T option to tell indent the name of all the
typenames in your program that are defined by typedef. -T can be
specified more than once, and all names specified are used. For
example, if your program contains
typedef unsigned long CODE_ADDR;
typedef enum {red, blue, green} COLOR;
you would use the options -T CODE_ADDR -T COLOR.
The -brs or -bls option specifies how to format braces in struct
declarations. The -brs option formats braces like this:
struct foo {
int x;
};
- 21 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
The -bls option formats them like this:
struct foo
{
int x;
};
Similarly to the structure brace -brs and -bls options,
the function brace options -brf or -blf specify how to format the
braces in function definitions. The -brf option formats braces like
this:
int one(void) {
return 1;
};
The -blf option formats them like this:
int one(void)
{
return 1;
};
The -sar option affects how indent will render initializer lists.
Without -sar they are formatted like this:
int a[] = {1, 2, 3, 4};
struct s {
const char *name;
int x;
} a[] = {
{"name", 0},
{"a", 1}
};
With -sar they are formatted like this, with spaces inside the braces:
int a[] = { 1, 2, 3, 4 };
struct s {
const char *name;
int x;
} a[] = {
{ "name", 0 },
{ "a", 1 }
};
- 22 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
INDENTATION
The most basic, and most controversial issues with regard to code
formatting is precisely how indentation should be acoomplished.
Fortunately, indent supports several different styles of identation.
The default is to use tabs for indentation, which is specified by the
-ut option. Assuming the default tab size of 8, the code would look
like this:
int a(int b)
{
return b;
|------|
1 tab
}
For those that prefer spaces to tabs, indent provides the -nut option.
The same code would look like this:
int a(int b)
{
return b;
|------|
8 spaces
}
Another 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
broken across two lines, the second line is indented by a number of
additional spaces specified by the -ci option. -ci defaults to 0.
However, if the -lp option is specified, and a line has a left
parenthesis which 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 initialization lists. For example, a piece of
continued code might look like this with -nlp -ci3 in effect:
p1 = first_procedure (second_procedure (p2, p3),
third_procedure (p4, p5));
With -lp in effect the code looks somewhat clearer:
p1 = first_procedure (second_procedure (p2, p3),
third_procedure (p4, p5));
When a statement is broken in between two or more paren pairs (...),
each extra pair causes the indentation level extra indentation:
if ((((i < 2 &&
- 23 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
k > 0) || p == 0) &&
q == 1) ||
n = 0)
The option -ipN can be used to set the extra offset per paren. For
instance, -ip0 would format the above as:
if ((((i < 2 &&
k > 0) || p == 0) &&
q == 1) ||
n = 0)
indent assumes that tabs are placed 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.
By default, indent will use tabs to indent as far as possible, and
then pad with spaces until the desired position is reached. However,
with the -as option, spaces will be used for alignment beyond the
current indentation level. By default, assuming -lp is enabled, the
code would be indented like so (t represents tabs, s represents
spaces):
unsigned long really_long_proc_name(unsigned long x, unsigned long y,
int a)
|------||-------||------||-------|__
t t t t ss
{
p1 = first_procedure (second_procedure (p2, p3),
third_procedure (p4, p5));
|------||------||------|_____
t t t sssss
}
This is fine, if you assume that whoever is reading the code will
honor your assumption of 8-space tabs. If the reader was using 4-space
tabs, it would look like this:
unsigned long really_long_proc_name(unsigned long x, unsigned long y,
int a)
|---||---||---||---|__
t t t t ss
{
p1 = first_procedure (second_procedure (p2, p3),
third_procedure (p4, p5));
|---||---||---|______
t t t ssssss
}
The -as option fixes this so that the code will appear consistent
- 24 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
regardless of what tab size the user users to read the code. This
looks like:
unsigned long really_long_proc_name(unsigned long x, unsigned long y,
int a)
____________________________________
ssssssssssssssssssssssssssssssssssss
{
p1 = first_procedure (second_procedure (p2, p3),
third_procedure (p4, p5));
|------|______________________
t ssssssssssssssssssssss
}
The indentation of type declarations in old-style function definitions
is controlled by the -ip parameter. This is a numeric parameter
specifying how many spaces to indent type declarations. 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.
ANSI C allows white space to be placed on preprocessor command lines
between the character # and the command name. By default, indent
removes this space, but specifying directs indent to leave this space
unmodified. The option -ppi overrides -nlps and -lps.
This option can be used to request that preprocessor conditional
statements can be indented by to given number of spaces, for example
with the option -ppi 3
#if X
#if Y
#define Z 1
#else
#define Z 0
#endif
#endif
becomes
#if X
# if Y
# define Z 1
- 25 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
# else
# define Z 0
# endif
#endif
This option sets the offset at which a label (except case labels) will
be positioned. If it is set to zero or a positive number, this
indicates how far from the left margin to indent a label. If it is
set to a negative number, this indicates how far back from the current
indent level to place the label. The default setting is -2 which
matches the behaviour of earlier versions of indent. Note that this
parameter does not affect the placing of case labels; see the -cli
parameter for that. For example with the option -il 1
group
function()
{
if (do_stuff1() == ERROR)
goto cleanup1;
if (do_stuff2() == ERROR)
goto cleanup2;
return SUCCESS;
cleanup2:
do_cleanup2();
cleanup1:
do_cleanup1();
return ERROR;
}
becomes
group
function()
{
if (do_stuff1() == ERROR)
goto cleanup1;
if (do_stuff2() == ERROR)
goto cleanup2;
return SUCCESS;
cleanup2:
do_cleanup2();
cleanup1:
do_cleanup1();
- 26 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
return ERROR;
}
BREAKING LONG LINES
With the option -ln, or --line-lengthn, it is possible to specify the
maximum length of a line of C code, not including possible comments
that follow it.
When lines become longer than the specified line length, GNU indent
tries to break the line at a logical place. This is new as of version
2.1 however and not very intelligent or flexible yet.
Currently there are three options that allow one to interfere with the
algorithm that determines where to break a line.
The -bbo option causes GNU indent to prefer to break long lines before
the boolean operators && and ||. The -nbbo option causes GNU indent
not have that preference. For example, the default option -bbo
(together with --line-length60 and --ignore-newlines) makes code look
like this:
if (mask
&& ((mask[0] == \0)
|| (mask[1] == \0
&& ((mask[0] == 0) || (mask[0] == *)))))
Using the option -nbbo will make it look like this:
if (mask &&
((mask[0] == \0) ||
(mask[1] == \0 &&
((mask[0] == 0) || (mask[0] == *)))))
The default -hnl, however, honours newlines in the input file by
giving them the highest possible priority to break lines at. For
example, when the input file looks like this:
if (mask
&& ((mask[0] == \0)
|| (mask[1] == \0 && ((mask[0] == 0) || (mask[0] == *)))))
then using the option -hnl, or --honour-newlines, together with the
previously mentioned -nbbo and --line-length60, will cause the output
not to be what is given in the last example but instead will prefer to
break at the positions where the code was broken in the input file:
if (mask
&& ((mask[0] == \0)
|| (mask[1] == \0 &&
((mask[0] == 0) || (mask[0] == *)))))
- 27 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
The idea behind this option is that lines which are too long, but are
already broken up, will not be touched by GNU indent. Really messy
code should be run through indent at least once using the --ignore-
newlines option though.
The -gts option affects how the gettext standard macros _() and N_()
are treated. The default behavior (or the use of -ngts) causes indent
to treat them as it does other functions, so that a long string is
broken like the following example.
if (mask)
{
warning (_
("This is a long string that stays together."));
}
With the -gts option, the underscore is treated as a part of the
string, keeping it tied to the string, and respecting the fact that
gettext is unobtrusively providing a localized string. This only
works if _(" is together as a unit at the beginning of the string and
") is together as a unit at the end.
if (mask)
{
warning
(_("This is a long string that stays together."));
}
DISABLING FORMATTING
Formatting of C code may be disabled for portions of a program by
embedding special control comments in the program. To turn off
formatting for a section of a program, place the disabling control
comment /* *INDENT-OFF* */ on a line by itself just before that
section. Program text scanned after this control comment is output
precisely as input with no modifications until the corresponding
enabling comment is scanned on a line by itself. The enabling control
comment is /* *INDENT-ON* */, and any text following the comment on
the line is also output unformatted. Formatting begins again with the
input line following the enabling control comment.
More precisely, indent does not attempt to verify the closing
delimiter (*/) for these C comments, and any whitespace on the line is
totally transparent.
These control comments also function in their C++ formats, namely //
*INDENT-OFF* and // *INDENT-ON*.
It should be noted that the internal state of indent remains unchanged
over the course of the unformatted section. Thus, for example,
turning off formatting in the middle of a function and continuing it
- 28 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
after the end of the function may lead to bizarre results. It is
therefore wise to be somewhat modular in selecting code to be left
unformatted.
As a historical note, some earlier versions of indent produced error
messages beginning with *INDENT**. These versions of indent were
written to ignore any with such error messages. I have removed this
incestuous feature from GNU indent.
MISCELLANEOUS OPTIONS
To find out what version of indent you have, use the command indent
-version. This will report the indent, without doing any of the
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
more lines of output, and gives some size statistics at completion.
The -pmt option causes indent to preserve the access and modification
times on the output files. Using this option has the advantage that
running indent on all source and header files in a project wont cause
make to rebuild all targets. This option is only available on
Operating Systems that have the POSIX utime(2) function.
BUGS
Please report any bugs to bug-indent@gnu.org.
When indent is run twice on a file, with the same profile, it should
never change that file the second time. With the current design of
indent, this can not be guaranteed, and it has not been extensively
tested.
indent does not understand C. In the inability to join lines. The
result is that running a file through indent is irreversible, even if
the used input file was the result of running indent with a given
profile (.indent.pro).
While an attempt was made to get indent working for C++, it will not
do a good job on any C++ source except the very simplest.
indent does not look at the when writing comments to the output file.
This results often in comments being put far to the right. In order
to prohibit indent from joining a broken line that has a comment at
the end, make sure that the comments start on the first line of the
break.
indent does not count lines and option) when indent is turned off with
/* *INDENT-OFF* */.
Comments of the form /*UPPERCASE*/ are not treated as comment but as
- 29 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
an identifier, causing them to be joined with the next line. This
renders comments of this type useless, unless they are embedded in the
code to begin with.
COPYRIGHT
The following copyright notice applies to the indent program. The
copyright and copying permissions for this manual appear near the
beginning of indent.texinfo and indent.info, and near the end of
indent.1.
Copyright (c) 2015 Tim Hentenaar.
Copyright (c) 2001 David Ingamells.
Copyright (c) 1999 Carlo Wood.
Copyright (c) 1995, 1996 Joseph Arceneaux.
Copyright (c) 1989, 1992, 1993, 1994, 1995, 1996, 2014 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
provided 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, Berkeley, 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
PURPOSE.
Options Cross Key
Here is a list of options alphabetized by long option, to help you
find the corresponding short option.
--align-with-spaces -as
--blank-lines-after-commas -bc
--blank-lines-after-declarations -bad
--blank-lines-after-procedures -bap
--blank-lines-before-block-comments -bbb
--braces-after-if-line -bl
--braces-after-func-def-line -blf
--brace-indent -bli
--braces-after-struct-decl-line -bls
--braces-on-if-line -br
- 30 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
--braces-on-func-def-line -brf
--braces-on-struct-decl-line -brs
--break-after-boolean-operator -nbbo
--break-before-boolean-operator -bbo
--break-function-decl-args -bfda
--break-function-decl-args-end -bfde
--case-indentation -clin
--case-brace-indentation -cbin
--comment-delimiters-on-blank-lines -cdb
--comment-indentation -cn
--continuation-indentation -cin
--continue-at-parentheses -lp
--cuddle-do-while -cdw
--cuddle-else -ce
--declaration-comment-column -cdn
--declaration-indentation -din
--dont-break-function-decl-args -nbfda
--dont-break-function-decl-args-end -nbfde
--dont-break-procedure-type -npsl
--dont-cuddle-do-while -ncdw
--dont-cuddle-else -nce
--dont-format-comments -nfca
--dont-format-first-column-comments -nfc1
--dont-line-up-parentheses -nlp
--dont-left-justify-declarations -ndj
--dont-space-special-semicolon -nss
--dont-star-comments -nsc
--dont-tab-align-comments -ntac
--else-endif-column -cpn
--format-all-comments -fca
--format-first-column-comments -fc1
--gnu-style -gnu
--honour-newlines -hnl
--ignore-newlines -nhnl
--ignore-profile -npro
--indent-label -iln
--indent-level -in
--k-and-r-style -kr
--leave-optional-blank-lines -nsob
--leave-preprocessor-space -lps
--left-justify-declarations -dj
--line-comments-indentation -dn
--line-length -ln
--linux-style -linux
--no-blank-lines-after-commas -nbc
--no-blank-lines-after-declarations -nbad
--no-blank-lines-after-procedures -nbap
--no-blank-lines-before-block-comments -nbbb
--no-comment-delimiters-on-blank-lines -ncdb
--no-space-after-casts -ncs
--no-parameter-indentation -nip
- 31 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
--no-space-after-for -nsaf
--no-space-after-function-call-names -npcs
--no-space-after-if -nsai
--no-space-after-parentheses -nprs
--no-space-after-while -nsaw
--no-tabs -nut
--no-verbosity -nv
--original -orig
--parameter-indentation -ipn
--paren-indentation -pin
--preserve-mtime -pmt
--preprocessor-indentation -ppin
--procnames-start-lines -psl
--remove-preprocessor-space -nlps
--single-line-conditionals -slc
--space-after-cast -cs
--space-after-for -saf
--space-after-if -sai
--space-after-parentheses -prs
--space-after-procedure-calls -pcs
--space-after-while -saw
--space-special-semicolon -ss
--spaces-around-initializers -sar
--standard-output -st
--start-left-side-of-comments -sc
--struct-brace-indentation -sbin
--swallow-optional-blank-lines -sob
--tab-size -tsn
--use-tabs -ut
--verbose -v
RETURN VALUE
+ 0 means no errors or warnings were found during a successful
invocation of the program.
+ 2 is returned if errors occur during formatting which do not prevent
completion of the formatting, but which appear to be manifested by
incorrect code (i.e. code which wouldn't compile).
+ 3 is returned if formatting of a file is halted because of an error
with the file which prevents completion of formatting. If more than
one input file was specified, indent continues to the next file.
+ 4 is returned if a serious internal problem occurs and the entire
indent process is terminated, even if all specified files have not
been processed.
+ 64 is returned if an invocation problem (like an incorrect option)
prevents any formatting to occur.
- 32 - Formatted: November 2, 2025
INDENT(1) INDENT(1)
FILES
$HOME/.indent.pro holds default options for indent.
AUTHORS
Tim Hentenaar
Carlo Wood
Joseph Arceneaux
Jim Kingdon
David Ingamells
HISTORY
Derived from the UCB program "indent".
COPYING
Copyright (C) 1989, 1992, 1993, 1994, 1995, 1996, 2014, 2015 Free
Software Foundation, Inc. Copyright (C) 1995, 1996 Joseph Arceneaux.
Copyright (C) 1999 Carlo Wood. Copyright (C) 2001 David Ingamells.
Copyright (C) 2013 ukasz Stelmach. Copyright (C) 2015 Tim
Hentenaar.
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.
- 33 - Formatted: November 2, 2025
