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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

       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

   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.,

              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

   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

       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      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

                     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       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 pages.

       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

       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 applications:

                            *  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

       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

       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 activities.

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

       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

           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 example

           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.

       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

       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 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

       *  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