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       man-pages - conventions for writing Linux man pages


       man [section] title


       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, as well
       as many of the pages that appear in Sections 3, 4, 5, and 7 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 Commands (Programs)
                 Those commands that can be executed by the user from within a shell.

       2 System calls
                 Those functions which must be performed by the kernel.

       3 Library calls
                 Most of the libc functions.

       4 Special files (devices)
                 Files found in /dev.

       5 File formats and conventions
                 The format for /etc/passwd and other human-readable files.

       6 Games

       7 Overview, conventions, and miscellaneous
                 Overviews of various topics, conventions and protocols, character set standards,
                 and miscellaneous other things.

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

   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 macros.

   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

       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 revision—remember to change this every time a change
                        is  made  to  the  man  page, since this is the most general way of doing
                        version control.  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 list.

            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]
            ATTRIBUTES         [Normally only in Sections 2, 3]
            VERSIONS           [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 sections.

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

       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

       SYNOPSIS      briefly  describes  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   gives an explanation of what the program, function, or format does.  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 section.

                     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

                             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       describes 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

       EXIT STATUS   lists  the  possible exit status values of a program and the conditions that
                     cause these values to be returned.  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 returned.

       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 errors.  The error list should be in alphabetical order.

       ENVIRONMENT   lists  all environment variables that affect the program or function and how
                     they affect it.

       FILES         lists 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,
                     broken into subsections.  The following subsections are defined:

                     Multithreading (see pthreads(7))
                            This  subsection   notes   attributes   relating   to   multithreaded

                            *  Whether the function is thread-safe.

                            *  Whether the function is a cancellation point.

                            *  Whether the function is async-cancel-safe.

                            Details of these attributes can be found in pthreads(7).

       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 2.0).

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

       CONFORMING TO describes  any  standards  or  conventions  that  relate  to the function or
                     command described by the manual page.  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 POSIX.1.)  (See standards(7).)

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

       BUGS          lists limitations, known defects or inconveniences, and  other  questionable

       EXAMPLE       provides  one or more examples describing how this function, file or command
                     is used.  For details on writing  example  programs,  see  Example  Programs

       AUTHORS       lists 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      provides a comma-separated list of related man  pages,  ordered  by  section
                     number  and  then alphabetically by name, possibly followed by other related
                     pages or documents.  Do not terminate this 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

   Font conventions
       For functions, the arguments are always specified using  italics,  even  in  the  SYNOPSIS
       section, where the rest of the function is specified in bold:

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

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

       Filenames  (whether  pathnames,  or references to files in the /usr/include directory) 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 include file under
       /usr/include, specify the header file surrounded by angle brackets, in  the  usual  C  way
       (e.g., <stdio.h>).

       Special  macros,  which are usually in upper case, 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 in an indented line on their own, 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.,

       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.

       Any reference to the subject of the current manual page should be written with the name in
       bold.  If the subject is a function (i.e., this is a Section 2 or 3 page), then  the  name
       should  be  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.)

       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.)

       Starting  with release 2.59, man-pages follows American spelling conventions; please write
       all new pages and patches according to these conventions.

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

   Example programs and shell sessions
       Manual pages can 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 purpose.

       *  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

       *  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!)

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

       If you include a shell session demonstrating the use of a program or other system feature,
       boldface the user input text, to distinguish it from output produced by the system.

   Indentation of structure definitions, shell session logs, etc.
       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).


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


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


       This page is part of release 3.54 of the Linux man-pages project.  A  description  of  the
       project,     and    information    about    reporting    bugs,    can    be    found    at