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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-section

       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  name and version of the project that provides the manual page (not necessarily
              the package that provides the functionality).

              Normally, this should be empty, since the default value will be good.

   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.

              LIBRARY          [Normally only in Sections 2, 3]
              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]
              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.

              The library providing a symbol.

              It  shows  the  common  name  of  the  library, and in parentheses, the name of the
              library file and, if needed, the linker flag needed to link a program  against  it:
              (libfoo[, -lfoo]).

              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 Linux 2.2), and  library
              functions  that have been added to glibc since glibc 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.

              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.

              Warnings about typical user misuse of an API, that don't constitute an API  bug  or
              design defect.

       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  note  some  details  for  preferred  formatting  and  wording
       conventions in various sections of the pages in the man-pages project.

       Wrap the function prototype(s) in a .nf/.fi pair to prevent filling.

       In general, where more  than  one  function  prototype  is  shown  in  the  SYNOPSIS,  the
       prototypes  should  not be separated by blank lines.  However, blank lines (achieved using
       .PP) may be added in the following cases:

       •  to separate long lists of function prototypes into  related  groups  (see  for  example

       •  in other cases that may improve readability.

       In the SYNOPSIS, a long function prototype may need to be continued over to the next line.
       The continuation line is indented according to the following rules:

       (1)  If there is a single such prototype that  needs  to  be  continued,  then  align  the
            continuation  line  so  that  when  the page is rendered on a fixed-width font device
            (e.g., on an xterm) the continuation line starts just below the start of the argument
            list  in the line above.  (Exception: the indentation may be adjusted if necessary to
            prevent a very long continuation line  or  a  further  continuation  line  where  the
            function prototype is very long.)  As an example:

                int tcsetattr(int fd, int optional_actions,
                              const struct termios *termios_p);

       (2)  But,  where  multiple  functions  in the SYNOPSIS require continuation lines, and the
            function names have different lengths, then align all continuation lines to start  in
            the same column.  This provides a nicer rendering in PDF output (because the SYNOPSIS
            uses a variable width font where spaces render narrower than most characters).  As an

                int getopt(int argc, char * const argv[],
                           const char *optstring);
                int getopt_long(int argc, char * const argv[],
                           const char *optstring,
                           const struct option *longopts, int *longindex);

       The preferred wording to describe how errno is set is "errno is set to indicate the error"
       or similar.  This wording is consistent with the wording used in both POSIX.1 and FreeBSD.

       Note the following:

       •  Wrap the table in this section in a .ad l/.ad  pair  to  disable  text  filling  and  a
          .nh/.hy pair to disable hyphenation.

       •  Ensure  that  the  table  occupies  the  full  page  width  through  the  use of an lbx
          description for one of the columns (usually the first column, though in some cases  the
          last column if it contains a lot of text).

       •  Make  free  use  of  T{/T}  macro pairs to allow table cells to be broken over multiple
          lines (also bearing in mind that pages may sometimes be rendered to  a  width  of  less
          than 80 columns).

       For examples of all of the above, see the source code of various pages.


       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, long
       sentences should be split into lines at clause breaks (commas, semicolons, colons, and  so
       on),  and  long  clauses should be split at phrase boundaries.  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, clauses, or phrases.

       There are different kinds of lists:

       Tagged paragraphs
              These  are  used  for  a  list  of  tags and their descriptions.  When the tags are
              constants (either macros or numbers) they are in bold.  Use the .TP macro.

              An example is this "Tagged paragraphs" subsection is itself.

       Ordered lists
              Elements are preceded by a number in parentheses (1), (2).  These represent  a  set
              of steps that have an order.

              When there are substeps, they will be numbered like (4.2).

       Positional lists
              Elements  are  preceded  by  a  number  (index) in square brackets [4], [5].  These
              represent fields in a set.  The first index will be:

              0      When it represents fields of a C  data  structure,  to  be  consistent  with
              1      When  it  represents  fields  of  a  file,  to be consistent with tools like

       Alternatives list
              Elements are preceded by a letter in parentheses (a), (b).  These represent  a  set
              of (normally) exclusive alternatives.

       Bullet lists
              Elements  are  preceded  by  bullet  symbols  (\[bu]).   Anything  that doesn't fit
              elsewhere is usually covered by this type of list.

       Numbered notes
              Not really a list, but the syntax is identical to "positional lists".

       There should always be exactly 2 spaces between the list symbol and  the  elements.   This
       doesn't apply to "tagged paragraphs", which use the default indentation rules.

   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  (\[ti])
       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.

       •  Opinions   are  divided  on  "acknowledgement"  vs  "acknowledgment".   The  latter  is
          predominant, but not universal usage in American English.  POSIX and  the  BSD  license
          use the former spelling.  In the Linux man-pages project, we use "acknowledgement".

   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 UTC)
       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-
       symbolic link        symlink
       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 byte
       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.

       The use of real minus signs serves the following purposes:

       •  To provide better renderings on various targets other than ASCII terminals, notably  in
          PDF and on Unicode/UTF-8-capable terminals.

       •  To  generate  glyphs that when copied from rendered pages will produce real minus signs
          when pasted into a terminal.

       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 PDF.

   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 is appreciated.

       •  Comments  should  included where helpful.  Complete sentences in free-standing comments
          should be terminated by a  period.   Periods  should  generally  be  omitted  in  "tag"
          comments  (i.e.,  comments that are placed on the same line of code); such comments are
          in any case typically brief phrases rather than complete sentences.

       •  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)