man-pages


SYNOPSIS
       man [section] title

DESCRIPTION
       This  page describes the conventions that should be employed when writ-
       ing 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, char-
                 acter 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  charac-
       ters  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 individ-
              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 prac-
                        tice  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.

            NAME
            SYNOPSIS
            CONFIGURATION      [Normally only in Section 4]
            DESCRIPTION
            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]
            ENVIRONMENT
            FILES
            ATTRIBUTES         [Normally only in Sections 2, 3]
            VERSIONS           [Normally only in Sections 2, 3]
            CONFORMING TO
            NOTES
            BUGS
            EXAMPLE
            SEE ALSO

       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  conven-
                     tion 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  nor-
                     mally 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 sec-
                     tion.

                     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
                     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  pro-
                     grams,   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) docu-
                     mented on this page, broken into subsections.   The  fol-
                     lowing subsections are defined:


                     Multithreading (see pthreads(7))
                            This  subsection notes attributes relating to mul-
                            tithreaded 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
                            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  sec-
                     tion  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
                     (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 func-
                     tion, 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  sig-
                     nificantly amend a page, add a copyright notice as a com-
                     ment in the source file.  If you  are  the  author  of  a
                     device  driver and want to include an address for report-
                     ing 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  docu-
                     ments.  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  indi-
                     vidual  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.


       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 writ-
       ten 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  eas-
       ier 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  (nor-
       mal)  font,  without  any separating spaces (e.g., intro(2)).  The pre-
       ferred 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.)

   Spelling
       Starting with release 2.59, man-pages follows American spelling conven-
       tions; please write all new pages and patches according to  these  con-
       ventions.

   Capitalization
       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  descrip-
          tion  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.

       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).

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

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

COLOPHON
       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 http://www.kernel.org/doc/man-pages/.



Linux                             2013-07-24                      MAN-PAGES(7)
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