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Updated: June 2017
 
 

indent(1)

Name

indent - indent and format a C program source file

Synopsis

indent input-file [ output-file ] [ [ -bap | -nbap ]
     [ -bacc | -nbacc ] [ -bad | -nbad ] [ -bbb | -nbbb ]
     [ -bc | -nbc ] [ -bl ] [ -br ] [ -bs | -nbs ] [ -cn ]
     [ -cdn ] [ -cdb | -ncdb ] [ -ce | -nce ] [ -cin ] [ -clin ]
     [ -dn ] [ -din ] [ -dj | -ndj ] [ -eei | -neei ]
     [ -ei | -nei ] [ -fc1 | -nfc1 ] [ -in ] [ -ip | -nip ]
     [ -ln ] [ -lcn ] [ -lp | -nlp ] [ -pcs | -npcs ] [ -npro ]
     [ -psl | -npsl ] [ -sc | -nsc ] [ -sob | -nsob ] [ -st ]
     [ -T typename ] [ -troff ] [ -v | -nv ]

Description

indent is a C program formatter. It reformats the C program in the input-file according to the switches. The switches which can be specified are described below. They may appear before or after the file names.

Note: if you only specify an input-file, the formatting is done "in-place", that is, the formatted file is written back into input-file and a backup copy of input-file is written in the current directory. If input-file is named /blah/blah/file, the backup file is named file.BAK.

If output-file is specified, indent checks to make sure it is different from input-file.

Options

The options listed below control the formatting style imposed by indent.

-bacc,-nbacc

If -bacc is specified, a blank line is forced around every conditional compilation block. For example, in front of every #ifdef and after every #endif. Other blank lines surrounding these will be swallowed. Default: -nbacc.

-bad,-nbad

If -bad is specified, a blank line is forced after every block of declarations. Default: -nbad.

-bap,-nbap

If -bap is specified, a blank line is forced after every procedure body. Default: -nbap.

-bbb,-nbbb

If -bbb is specified, a blank line is forced before every block comment. Default: -nbbb.

-bc,-nbc

If -bc is specified, then a NEWLINE is forced after each comma in a declaration. -nbc turns off this option. Default: -bc.

-br,-bl

Specifying -bl lines up compound statements like this:

 
if (...)
{
               code
}

Specifying -br (the default) makes them look like this:

 
if (...) {
               code
}
-bs,-nbs

Enable (disable) the forcing of a blank after sizeof. Some people believe that sizeof should appear as though it were a procedure call (-nbs, the default) and some people believe that since sizeof is an operator, it should always be treated that way and should always have a blank after it.

-cn

The column in which comments on code start. The default is -c33.

-cdn

The column in which comments on declarations start. The default is for these comments to start in the same column as those on code.

-cdb,-ncdb

Enable (disable) the placement of comment delimiters on blank lines. With this option enabled, comments look like this:

 
/*
* this is a comment
*/

Rather than like this:

/* this is a comment */

This only affects block comments, not comments to the right of code. Default: -cdb.

-ce,-nce

Enables (disables) forcing else's to cuddle up to the immediately preceding `}'. Default: -ce.

-cin

Sets the continuation indent to be the value of n. Continuation lines will be indented the value of n from the beginning of the first line of the statement. Parenthesized expressions have extra indentation added to indicate the nesting, unless -lp is in effect. -ci defaults to the same value as -i.

-clin

Cause case labels to be indented n tab stops to the right of the containing switch statement. -cli0.5 causes case labels to be indented half a tab stop. Default: -cli0.

-dn

Control the placement of comments which are not to the right of code. Default: -d1 means that such comments are placed one indentation level to the left of code. Specifying -d0 lines up these comments with the code. See the section on comment indentation below.

-din

Specify the indentation, in character positions, from a declaration keyword to the following identifier. Default: -di16.

-dj,-ndj

-dj left justifies declarations. -ndj indents declarations the same as code. Default: -ndj.

-ei,-nei

If -ei is enabled, ifs following elses will have the same indentation as the preceding if statement. If it is disabled, ifs following elses will be indented one extra level. Default: -ei.

-eei,-neei

If -eei is specified, an extra expression indent is applied on continuation lines of the expression part of if() and while(). These continuation lines will be indented one extra level -- twice instead of just once. This is to avoid the confusion between the continued expression and the statement that follows the if() or while(). Default: -neei.

-fc1,-nfc1

Enables (disables) the formatting of comments that start in column 1. Often, comments whose leading `/' is in column 1 have been carefully hand formatted by the programmer. In such cases, -nfc1 should be used. Default: -fc1.

-in

The number of spaces for one indentation level. The default is one tab stop, -i8.

-ip,-nip

Enables (disables) the indentation of parameter declarations from the left margin. Default: -ip .

-ln

Maximum length of an output line with a trailing comment. Default: -l78.

-lcn

Sets the line length for block comments to n. It defaults to being the same as the usual line length as specified with -l.

-lp,-nlp

Lines up code surrounded by parenthesis in continuation lines. If 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. For example, here is how a piece of continued code looks with -nlp in effect:

 
p1 = first_procedure(second_procedure(p2, p3),
               third_procedure(p4, p5));

With -lp in effect (the default) the code looks somewhat clearer:

 
p1 = first_procedure(second_procedure(p2, p3),
                       third_procedure(p4, p5));

Inserting a couple more NEWLINE characters we get:

 
p1 = first_procedure(second_procedure(p2, p3),         
                       third_procedure(p4, p5));

This example was generated with -lp.

-npro

Ignore the profile files, ./.indent.pro and ~/.indent.pro.

-pcs , -npcs

If true (-pcs) all procedure calls and declarations in the source code will have a space inserted between the name and the '('. Default: -npcs.

-psl , -npsl

If true (-psl) the names of procedures being defined are placed in column 1 -- their types, if any, will be left on the previous lines. Default: -psl.

-sc,-nsc

Enables (disables) the placement of asterisks (`*'s) at the left edge of all comments. Default: -sc.

-sob,-nsob

If -sob is specified, indent will swallow optional blank lines. You can use this to get rid of blank lines after declarations. Default: -nsob.

-st

indent takes its input from the standard input, and put its output to the standard output.

-T typename

Add typename to the list of type keywords. Names accumulate: -T can be specified more than once. You need to specify all the typenames that appear in your program that are defined by typedefs -- nothing will be harmed if you miss a few, but the program won't be formatted as nicely as it should. This sounds like a painful thing to have to do, but it is really a symptom of a problem in C: typedef causes a syntactic change in the language and indent cannot find all typedefs.

-troff

Causes indent to format the program for processing by troff. It will produce a fancy listing in much the same spirit as vgrind. If the output file is not specified, the default is standard output, rather than formatting in place. The usual way to get a troffed listing is with the command

indent -troff program.c | troff -mindent
-v,-nv

-v turns on "verbose" mode, -nv turns it off. When in verbose mode, indent reports when it splits one line of input into two or more lines of output, and gives some size statistics at completion. Default: -nv.

Usage

You may set up your own "profile" of defaults to indent by creating a file called .indent.pro in either your login directory or the current directory and including whatever switches you like. An .indent.pro in the current directory takes precedence over the one in your login directory. If indent is run and a profile file exists, then it is read to set up the program's defaults. Switches on the command line, though, always override profile switches. The switches should be separated by SPACE, TAB, or NEWLINE characters.

Comments

Boxed

indent assumes that any comment with a dash or star immediately after the start of comment (that is, `/*-'or`/**') is a comment surrounded by a box of stars. Each line of such a comment is left unchanged, except that its indentation may be adjusted to account for the change in indentation of the first line of the comment.

Straight text

All other comments are treated as straight text. indent fits as many words (separated by SPACE, TAB, or NEWLINE characters) on a line as possible. Blank lines break paragraphs.

Comment indentation

If a comment is on a line with code it is started in the comment column, which is set by the -cn command line parameter. Otherwise, the comment is started at n indentation levels less than where code is currently being placed, where n is specified by the -dn command line parameter. 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.

Preprocessor lines

In general, indent leaves preprocessor lines alone. The only reformatting that it will do is to straighten up trailing comments. It leaves imbedded comments alone. Conditional compilation (#ifdef...#endif) is recognized and indent attempts to correctly compensate for the syntactic peculiarities introduced.

C syntax

indent understands a substantial amount about the syntax of C, but it has a "forgiving" parser. It attempts to cope with the usual sorts of incomplete and misformed syntax. In particular, the use of macros like:

#define forever for(;;)

is handled properly.

/*INDENT OFF*/ /*INDENT ON*/

All text between these two comments gets left alone. Therefore, when you put source code between these comments, it will not be affected by the reformatting.

Files

./.indent.pro

profile file

~/.indent.pro

profile file

See Also

troff(1)

Bugs

A common mistake that often causes grief is typing:

indent *.c

to the shell in an attempt to indent all the C programs in a directory.