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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, 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)
              Commands that can be executed by the user from within a shell.

       2 System calls
              Functions which wrap operations performed by the kernel.

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

       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 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

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

              .TH title section date source manual

       The arguments of the command are as follows:

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

              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

              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]
              VERSIONS         [Normally only in Sections 2, 3]
              ATTRIBUTES       [Normally only in Sections 2, 3]
              CONFORMING TO
              AUTHORS          [Discouraged]
              REPORTING BUGS   [Not used in man-pages]
              COPYRIGHT        [Not used in man-pages]
              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 otherwise.

              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

              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 details for a device.

              This section normally appears only in Section 4 pages.

              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 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

              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.

              A list of 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.

              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

              Where  several  different conditions produce the same error, the preferred approach
              is to create separate list entries (with duplicate error names)  for  each  of  the
              conditions.   This makes the separate conditions clear, may make the list easier to
              read, and allows metainformation (e.g., kernel version number where  the  condition
              first became applicable) to be more easily marked for each condition.

              The error list should be in alphabetical order.

              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.

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

              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.

              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

              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.)

              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 Notes.

              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

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

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

              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.

              The man-pages project doesn't  use  a  REPORTING  BUGS  section  in  manual  pages.
              Information  on reporting bugs is instead supplied in the script-generated COLOPHON
              section.  However, various projects  do  use  a  REPORTING  BUGS  section.   it  is
              recommended to place it near the foot of the page.

              The  man-pages  project doesn't use a COPYRIGHT section in manual pages.  Copyright
              information is instead maintained in the page source.  In pages where this  section
              is present, it is recommended to place it near the foot of the page, just above SEE

       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.


       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 commands
       For manual pages that describe a 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 bold:

           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.)

   Use semantic newlines
       In  the  source  of  a manual page, new sentences should be started on new lines, and long
       sentences should split into lines at clause breaks (commas,  semicolons,  colons,  and  so
       on).   This convention, sometimes known as "semantic newlines", makes it easier to see the
       effect of patches, which often operate at the level of individual  sentences  or  sentence

   Formatting conventions (general)
       Paragraphs  should  be  separated by suitable markers (usually either .PP or .IP).  Do not
       separate paragraphs using blank lines, as this results in poor rendering  in  some  output
       formats (such as PostScript and PDF).

       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 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.,

       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

       *  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 4.3.

       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), format them using the
       .EX and EE macros, and surround them with suitable paragraph markers (either .PP or  .IP).
       For example:

               .in +4n
               main(int argc, char *argv[])
                   return 0;

   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
       filename             file name
       filesystem           file system
       hostname             host name
       inode                i-node
       lowercase            lower case, lower-case
       nonzero              non-zero
       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-block
       timestamp            time stamp
       timezone             time zone
       uppercase            upper case, upper-case
       usable               useable
       user space           userspace
       username             user name
       x86-64               x86_64                     Except  if  referring to
                                                       result of "uname -m"  or
       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,
       current process   calling process         A common mistake made by
                                                 kernel programmers  when
                                                 writing man pages
       manpage           man page, manual page
       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

       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-terminated".

       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.", "cf.", and "a.k.a."
       should be avoided, in favor of suitable full wordings ("for example", "that is",  "and  so
       on", "compare to", "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.

   Generating optimal glyphs
       Where a real minus character is required (e.g., for numbers such as -1, for man page cross
       references  such as utf-8(7), 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.

       To produce unslanted single quotes that render well in ASCII, UTF-8, and PDF,  use  "\(aq"
       ("apostrophe quote"); for example


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

       Where a proper caret (^) that renders well in both a terminal and  PDF  is  required,  use
       "\(ha".  This is especially necessary in code samples, to get a nicely rendered caret when
       rendering to PDF.

       Using a naked "~" character results in a poor rendering in PDF.  Instead use "\(ti".  This
       is  especially necessary in code samples, to get a nicely rendered tilde when rendering to

   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 purpose.

       *  Example programs should ideally be short (e.g., a good example can often be provided in
          less than 100 lines of code), though in some cases longer programs may be necessary  to
          properly illustrate the use of an API.

       *  Expressive code and useful comments are appreciated.

       *  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!)   The  following
          command  can  be  used  to  format your source code to something close to the preferred

              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 log.

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

       *  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).


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


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


       This  page  is  part of release 5.10 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