MAN-PAGES(7)              Linux Programmer's Manual             MAN-PAGES(7)

NAME         top

       man-pages - conventions for writing Linux man pages

SYNOPSIS         top

       man [section] title

DESCRIPTION         top

       This page describes the conventions that should be employed when
       writing man pages for the Linux man-pages project, which documents
       the user-space API provided by the Linux kernel and the GNU C
       library.  The project thus provides most of the pages in Section 2,
       many of the pages that appear in Sections 3, 4, and 7, and a few of
       the pages that appear in Sections 1, 5, and 8 of the man pages on a
       Linux system.  The conventions described on this page may also be
       useful for authors writing man pages for other projects.

   Sections of the manual pages
       The manual Sections are traditionally defined as follows:

       1 User commands (Programs)
                 Those commands that can be executed by the user from within
                 a shell.

       2 System calls
                 Those functions which wrap operations performed by the

       3 Library calls
                 All library functions excluding the system call wrappers
                 (Most of the libc functions).

       4 Special files (devices)
                 Files found in /dev which allow to access to devices
                 through the kernel.

       5 File formats and configuration files
                 Describes various human-readable file formats and
                 configuration files.

       6 Games   Games and funny little programs available on the system.

       7 Overview, conventions, and miscellaneous
                 Overviews or descriptions of various topics, conventions
                 and protocols, character set standards, the standard
                 filesystem layout, and miscellaneous other things.

       8 System management commands
                 Commands like mount(8), many of which only root can

   Macro package
       New manual pages should be marked up using the groff an.tmac package
       described in man(7).  This choice is mainly for consistency: the vast
       majority of existing Linux manual pages are marked up using these

   Conventions for source file layout
       Please limit source code line length to no more than about 75
       characters wherever possible.  This helps avoid line-wrapping in some
       mail clients when patches are submitted inline.

       New sentences should be started on new lines.  This makes it easier
       to see the effect of patches, which often operate at the level of
       individual sentences.

   Title line
       The first command in a man page should be a TH command:

              .TH title section date source manual


              title     The title of the man page, written in all caps
                        (e.g., MAN-PAGES).

              section   The section number in which the man page should be
                        placed (e.g., 7).

              date      The date of the last nontrivial change that was made
                        to the man page.  (Within the man-pages project, the
                        necessary updates to these timestamps are handled
                        automatically by scripts, so there is no need to
                        manually update them as part of a patch.)  Dates
                        should be written in the form YYYY-MM-DD.

              source    The source of the command, function, or system call.

                        For those few man-pages pages in Sections 1 and 8,
                        probably you just want to write GNU.

                        For system calls, just write Linux.  (An earlier
                        practice was to write the version number of the
                        kernel from which the manual page was being
                        written/checked.  However, this was never done
                        consistently, and so was probably worse than
                        including no version number.  Henceforth, avoid
                        including a version number.)

                        For library calls that are part of glibc or one of
                        the other common GNU libraries, just use GNU C
                        Library, GNU, or an empty string.

                        For Section 4 pages, use Linux.

                        In cases of doubt, just write Linux, or GNU.

              manual    The title of the manual (e.g., for Section 2 and 3
                        pages in the man-pages package, use Linux
                        Programmer's Manual).

   Sections within a manual page
       The list below shows conventional or suggested sections.  Most manual
       pages should include at least the highlighted sections.  Arrange a
       new manual page so that sections are placed in the order shown in the

            CONFIGURATION      [Normally only in Section 4]
            OPTIONS            [Normally only in Sections 1, 8]
            EXIT STATUS        [Normally only in Sections 1, 8]
            RETURN VALUE       [Normally only in Sections 2, 3]
            ERRORS             [Typically only in Sections 2, 3]
            VERSIONS           [Normally only in Sections 2, 3]
            ATTRIBUTES         [Normally only in Sections 2, 3]
            CONFORMING TO
            SEE ALSO

       Where a traditional heading would apply, please use it; this kind of
       consistency can make the information easier to understand.  If you
       must, you can create your own headings if they make things easier to
       understand (this can be especially useful for pages in Sections 4 and
       5).  However, before doing this, consider whether you could use the
       traditional headings, with some subsections (.SS) within those

       The following list elaborates on the contents of each of the above

       NAME          The name of this manual page.

                     See man(7) for important details of the line(s) that
                     should follow the .SH NAME command.  All words in this
                     line (including the word immediately following the
                     "\-") should be in lowercase, except where English or
                     technical terminological convention dictates otherwise.

       SYNOPSIS      A brief summary of the command or function's interface.

                     For commands, this shows the syntax of the command and
                     its arguments (including options); boldface is used for
                     as-is text and italics are used to indicate replaceable
                     arguments.  Brackets ([]) surround optional arguments,
                     vertical bars (|) separate choices, and ellipses (...)
                     can be repeated.  For functions, it shows any required
                     data declarations or #include directives, followed by
                     the function declaration.

                     Where a feature test macro must be defined in order to
                     obtain the declaration of a function (or a variable)
                     from a header file, then the SYNOPSIS should indicate
                     this, as described in feature_test_macros(7).

       CONFIGURATION Configuration details for a device.

                     This section normally appears only in Section 4 pages.

       DESCRIPTION   An explanation of what the program, function, or format

                     Discuss how it interacts with files and standard input,
                     and what it produces on standard output or standard
                     error.  Omit internals and implementation details
                     unless they're critical for understanding the
                     interface.  Describe the usual case; for information on
                     command-line options of a program use the OPTIONS

                     When describing new behavior or new flags for a system
                     call or library function, be careful to note the kernel
                     or C library version that introduced the change.  The
                     preferred method of noting this information for flags
                     is as part of a .TP list, in the following form (here,
                     for a new system call flag):

                             XYZ_FLAG (since Linux 3.7)
                                    Description of flag...

                     Including version information is especially useful to
                     users who are constrained to using older kernel or C
                     library versions (which is typical in embedded systems,
                     for example).

       OPTIONS       A description of the command-line options accepted by a
                     program and how they change its behavior.

                     This section should appear only for Section 1 and 8
                     manual pages.

       EXIT STATUS   A list of the possible exit status values of a program
                     and the conditions that cause these values to be

                     This section should appear only for Section 1 and 8
                     manual pages.

       RETURN VALUE  For Section 2 and 3 pages, this section gives a list of
                     the values the library routine will return to the
                     caller and the conditions that cause these values to be

       ERRORS        For Section 2 and 3 manual pages, this is a list of the
                     values that may be placed in errno in the event of an
                     error, along with information about the cause of the

                     The error list should be in alphabetical order.

       ENVIRONMENT   A list of all environment variables that affect the
                     program or function and how they affect it.

       FILES         A list of the files the program or function uses, such
                     as configuration files, startup files, and files the
                     program directly operates on.

                     Give the full pathname of these files, and use the
                     installation process to modify the directory part to
                     match user preferences.  For many programs, the default
                     installation location is in /usr/local, so your base
                     manual page should use /usr/local as the base.

       ATTRIBUTES    A summary of various attributes of the function(s)
                     documented on this page.  See attributes(7) for further

       VERSIONS      A brief summary of the Linux kernel or glibc versions
                     where a system call or library function appeared, or
                     changed significantly in its operation.

                     As a general rule, every new interface should include a
                     VERSIONS section in its manual page.  Unfortunately,
                     many existing manual pages don't include this
                     information (since there was no policy to do so when
                     they were written).  Patches to remedy this are
                     welcome, but, from the perspective of programmers
                     writing new code, this information probably matters
                     only in the case of kernel interfaces that have been
                     added in Linux 2.4 or later (i.e., changes since kernel
                     2.2), and library functions that have been added to
                     glibc since version 2.1 (i.e., changes since glibc

                     The syscalls(2) manual page also provides information
                     about kernel versions in which various system calls
                     first appeared.

       CONFORMING TO A description of any standards or conventions that
                     relate to the function or command described by the
                     manual page.

                     The preferred terms to use for the various standards
                     are listed as headings in standards(7).

                     For a page in Section 2 or 3, this section should note
                     the POSIX.1 version(s) that the call conforms to, and
                     also whether the call is specified in C99.  (Don't
                     worry too much about other standards like SUS, SUSv2,
                     and XPG, or the SVr4 and 4.xBSD implementation
                     standards, unless the call was specified in those
                     standards, but isn't in the current version of

                     If the call is not governed by any standards but
                     commonly exists on other systems, note them.  If the
                     call is Linux-specific, note this.

                     If this section consists of just a list of standards
                     (which it commonly does), terminate the list with a
                     period ('.').

       NOTES         Miscellaneous notes.

                     For Section 2 and 3 man pages you may find it useful to
                     include subsections (SS) named Linux Notes and Glibc

                     In Section 2, use the heading C library/kernel
                     differences to mark off notes that describe the
                     differences (if any) between the C library wrapper
                     function for a system call and the raw system call
                     interface provided by the kernel.

       BUGS          A list of limitations, known defects or inconveniences,
                     and other questionable activities.

       EXAMPLE       One or more examples demonstrating how this function,
                     file or command is used.

                     For details on writing example programs, see Example
                     Programs below.

       AUTHORS       A list of authors of the documentation or program.

                     Use of an AUTHORS section is strongly discouraged.
                     Generally, it is better not to clutter every page with
                     a list of (over time potentially numerous) authors; if
                     you write or significantly amend a page, add a
                     copyright notice as a comment in the source file.  If
                     you are the author of a device driver and want to
                     include an address for reporting bugs, place this under
                     the BUGS section.

       SEE ALSO      A comma-separated list of related man pages, possibly
                     followed by other related pages or documents.

                     The list should be ordered by section number and then
                     alphabetically by name.  Do not terminate this list
                     with a period.

                     Where the SEE ALSO list contains many long manual page
                     names, to improve the visual result of the output, it
                     may be useful to employ the .ad l (don't right justify)
                     and .nh (don't hyphenate) directives.  Hyphenation of
                     individual page names can be prevented by preceding
                     words with the string "\%".

                     Given the distributed, autonomous nature of FOSS
                     projects and their documentation, it is sometimes
                     necessary—and in many cases desirable—that the SEE ALSO
                     section includes references to manual pages provided by
                     other projects.

STYLE GUIDE         top

       The following subsections describe the preferred style for the man-
       pages project.  For details not covered below, the Chicago Manual of
       Style is usually a good source; try also grepping for preexisting
       usage in the project source tree.

   Use of gender-neutral language
       As far as possible, use gender-neutral language in the text of man
       pages.  Use of "they" ("them", "themself", "their") as a gender-
       neutral singular pronoun is acceptable.

   Formatting conventions for manual pages describing functions
       For manual pages that describe command (typically in Sections 1 and
       8), the arguments are always specified using italics, even in the
       SYNOPSIS section.

       The name of the command, and its options, should always be formatted
       in bold.

   Formatting conventions for manual pages describing functions
       For manual pages that describe functions (typically in Sections 2 and
       3), the arguments are always specified using italics, even in the
       SYNOPSIS section, where the rest of the function is specified in

           int myfunction(int argc, char **argv);

       Variable names should, like argument names, be specified in italics.

       Any reference to the subject of the current manual page should be
       written with the name in bold followed by a pair of parentheses in
       Roman (normal) font.  For example, in the fcntl(2) man page,
       references to the subject of the page would be written as: fcntl().
       The preferred way to write this in the source file is:

           .BR fcntl ()

       (Using this format, rather than the use of "\fB...\fP()" makes it
       easier to write tools that parse man page source files.)

   Formatting conventions (general)
       Filenames (whether pathnames, or references to header files) are
       always in italics (e.g., <stdio.h>), except in the SYNOPSIS section,
       where included files are in bold (e.g., #include <stdio.h>).  When
       referring to a standard header file include, specify the header file
       surrounded by angle brackets, in the usual C way (e.g., <stdio.h>).

       Special macros, which are usually in uppercase, are in bold (e.g.,
       MAXINT).  Exception: don't boldface NULL.

       When enumerating a list of error codes, the codes are in bold (this
       list usually uses the .TP macro).

       Complete commands should, if long, be written as an indented line on
       their own, with a blank line before and after the command, for

           man 7 man-pages

       If the command is short, then it can be included inline in the text,
       in italic format, for example, man 7 man-pages.  In this case, it may
       be worth using nonbreaking spaces ("\ ") at suitable places in the
       command.  Command options should be written in italics (e.g., -l).

       Expressions, if not written on a separate indented line, should be
       specified in italics.  Again, the use of nonbreaking spaces may be
       appropriate if the expression is inlined with normal text.

       When showing example shell sessions, user input should be formatted
       in bold, for example

               $ date
               Thu Jul  7 13:01:27 CEST 2016

       Any reference to another man page should be written with the name in
       bold, always followed by the section number, formatted in Roman
       (normal) font, without any separating spaces (e.g., intro(2)).  The
       preferred way to write this in the source file is:

           .BR intro (2)

       (Including the section number in cross references lets tools like
       man2html(1) create properly hyperlinked pages.)

       Control characters should be written in bold face, with no quotes;
       for example, ^X.

       Starting with release 2.59, man-pages follows American spelling
       conventions (previously, there was a random mix of British and
       American spellings); please write all new pages and patches according
       to these conventions.

       Aside from the well-known spelling differences, there are a few other
       subtleties to watch for:

       *  American English tends to use the forms "backward", "upward",
          "toward", and so on rather than the British forms "backwards",
          "upwards", "towards", and so on.

   BSD version numbers
       The classical scheme for writing BSD version numbers is x.yBSD, where
       x.y is the version number (e.g., 4.2BSD).  Avoid forms such as BSD

       In subsection ("SS") headings, capitalize the first word in the
       heading, but otherwise use lowercase, except where English usage
       (e.g., proper nouns) or programming language requirements (e.g.,
       identifier names) dictate otherwise.  For example:

           .SS Unicode under Linux

   Indentation of structure definitions, shell session logs, and so on
       When structure definitions, shell session logs, and so on are
       included in running text, indent them by 4 spaces (i.e., a block
       enclosed by .in +4n and .in).

   Preferred terms
       The following table lists some preferred terms to use in man pages,
       mainly to ensure consistency across pages.

       Term                 Avoid using              Notes

       bit mask             bitmask
       built-in             builtin
       Epoch                epoch                    For the UNIX Epoch
                                                     (00:00:00, 1 Jan
                                                     1970 UTC)
       filename             file name
       filesystem           file system
       hostname             host name
       inode                i-node
       lowercase            lower case, lower-case
       pathname             path name
       pseudoterminal       pseudo-terminal
       privileged port      reserved port, system
       real-time            realtime, real time
       run time             runtime
       saved set-group-ID   saved group ID, saved
       saved set-user-ID    saved user ID, saved
       set-group-ID         set-GID, setgid
       set-user-ID          set-UID, setuid
       superuser            super user, super-user
       superblock           super block, super-
       timestamp            time stamp
       timezone             time zone
       uppercase            upper case, upper-case
       usable               useable
       user space           userspace
       username             user name
       zeros                zeroes

       See also the discussion Hyphenation of attributive compounds below.

   Terms to avoid
       The following table lists some terms to avoid using in man pages,
       along with some suggested alternatives, mainly to ensure consistency
       across pages.

       Avoid             Use instead         Notes

       32bit             32-bit              same for 8-bit,
                                             16-bit, etc.
       current process   calling process     A common mistake
                                             made by kernel
                                             programmers when
                                             writing man pages
       manpage           man page, manual
       minus infinity    negative infinity
       non-root          unprivileged user
       non-superuser     unprivileged user
       nonprivileged     unprivileged
       OS                operating system
       plus infinity     positive infinity
       pty               pseudoterminal
       tty               terminal
       Unices            UNIX systems
       Unixes            UNIX systems

       Use the correct spelling and case for trademarks.  The following is a
       list of the correct spellings of various relevant trademarks that are
       sometimes misspelled:


   NULL, NUL, null pointer, and null character
       A null pointer is a pointer that points to nothing, and is normally
       indicated by the constant NULL.  On the other hand, NUL is the null
       byte, a byte with the value 0, represented in C via the character
       constant '\0'.

       The preferred term for the pointer is "null pointer" or simply
       "NULL"; avoid writing "NULL pointer".

       The preferred term for the byte is "null byte".  Avoid writing "NUL",
       since it is too easily confused with "NULL".  Avoid also the terms
       "zero byte" and "null character".  The byte that terminates a C
       string should be described as "the terminating null byte"; strings
       may be described as "null-terminated", but avoid the use of "NUL-

       For hyperlinks, use the .UR/.UE macro pair (see groff_man(7)).  This
       produces proper hyperlinks that can be used in a web browser, when
       rendering a page with, say:

            BROWSER=firefox man -H pagename

   Use of e.g., i.e., etc., a.k.a., and similar
       In general, the use of abbreviations such as "e.g.", "i.e.", "etc.",
       "a.k.a."  should be avoided, in favor of suitable full wordings ("for
       example", "that is", "and so on", "also known as").

       The only place where such abbreviations may be acceptable is in short
       parenthetical asides (e.g., like this one).

       Always include periods in such abbreviations, as shown here.  In
       addition, "e.g." and "i.e." should always be followed by a comma.

       The way to write an em-dash—the glyph that appears at either end of
       this subphrase—in *roff is with the macro "\(em".  (On an ASCII
       terminal, an em-dash typically renders as two hyphens, but in other
       typographical contexts it renders as a long dash.)  Em-dashes should
       be written without surrounding spaces.

   Hyphenation of attributive compounds
       Compound terms should be hyphenated when used attributively (i.e., to
       qualify a following noun). Some examples:

           32-bit value
           command-line argument
           floating-point number
           run-time check
           user-space function
           wide-character string

   Hyphenation with multi, non, pre, re, sub, and so on
       The general tendency in modern English is not to hyphenate after
       prefixes such as "multi", "non", "pre", "re", "sub", and so on.
       Manual pages should generally follow this rule when these prefixes
       are used in natural English constructions with simple suffixes.  The
       following list gives some examples of the preferred forms:


       Hyphens should be retained when the prefixes are used in nonstandard
       English words, with trademarks, proper nouns, acronyms, or compound
       terms.  Some examples:


       Finally, note that "re-create" and "recreate" are two different
       verbs, and the former is probably what you want.

   Real minus character
       Where a real minus character is required (e.g., for numbers such as
       -1, or when writing options that have a leading dash, such as in
       ls -l), use the following form in the man page source:


       This guideline applies also to code examples.

   Character constants
       To produce single quotes that render well in both ASCII and UTF-8,
       use the following form for character constants in the man page


       where C is the quoted character.  This guideline applies also to
       character constants used in code examples.

   Example programs and shell sessions
       Manual pages may include example programs demonstrating how to use a
       system call or library function.  However, note the following:

       *  Example programs should be written in C.

       *  An example program is necessary and useful only if it demonstrates
          something beyond what can easily be provided in a textual
          description of the interface.  An example program that does
          nothing other than call an interface usually serves little

       *  Example programs should be fairly short (preferably less than 100
          lines; ideally less than 50 lines).

       *  Example programs should do error checking after system calls and
          library function calls.

       *  Example programs should be complete, and compile without warnings
          when compiled with cc -Wall.

       *  Where possible and appropriate, example programs should allow
          experimentation, by varying their behavior based on inputs
          (ideally from command-line arguments, or alternatively, via input
          read by the program).

       *  Example programs should be laid out according to Kernighan and
          Ritchie style, with 4-space indents.  (Avoid the use of TAB
          characters in source code!)  The following command can be used to
          format your source code to something close to the preferred style:

              indent -npro -kr -i4 -ts4 -sob -l72 -ss -nut -psl prog.c

       *  For consistency, all example programs should terminate using
          either of:


          Avoid using the following forms to terminate a program:

              return n;

       *  If there is extensive explanatory text before the program source
          code, mark off the source code with a subsection heading Program
          source, as in:

              .SS Program source

          Always do this if the explanatory text includes a shell session

       If you include a shell session log demonstrating the use of a program
       or other system feature:

       *  Place the session log above the source code listing

       *  Indent the session log by four spaces.

       *  Boldface the user input text, to distinguish it from output
          produced by the system.

       For some examples of what example programs should look like, see
       wait(2) and pipe(2).

EXAMPLE         top

       For canonical examples of how man pages in the man-pages package
       should look, see pipe(2) and fcntl(2).

SEE ALSO         top

       man(1), man2html(1), attributes(7), groff(7), groff_man(7), man(7),

COLOPHON         top

       This page is part of release 4.07 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                            2016-07-17                     MAN-PAGES(7)