indent(1) General Commands Manual indent(1)
NAME
indent - changes the appearance of a C program by inserting or deleting whitespace
SYNOPSIS
indent [-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 delimiters 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 operator.
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 column 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 parentheses.
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 cuddle } 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 parentheses.
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 * character 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 typenames. 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 Makeinfo-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 syn-
tax.
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 stan-
dard 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 stan-
dard. 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/metabolism.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 exception: 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 setting 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 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 numbered backups *already exist* for the file being indented; otherwise, a simple backup is made. If
VERSION_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 settings 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
comments 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 col-
umn comments. When comment formatting is disabled, overall comment indentation 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
comments 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 state-
ments 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 { fprintf (stderr, "...something wrong?
");
}
With -br -nce, that code would appear as follows:
if (x > 0) {
x--;
}
else { fprintf (stderr, "...something wrong?
");
}
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 operator.
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 posi-
tion. 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 follows:
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 continued from a previous line, it is indented by a number of additional
spaces 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 parenthe-
sis. This processing also applies to [ and applies to { when it occurs in initialization 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
specifying 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 copyright and copying permissions for this manual appear near the begin-
ning 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 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 spe-
cific prior written permission. THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITA-
TION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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)