man-pages(7) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | FORMATTING AND WORDING CONVENTIONS | STYLE GUIDE | EXAMPLES | SEE ALSO | COLOPHON

man-pages(7)        Miscellaneous Information Manual        man-pages(7)

NAME         top

       man-pages - conventions for writing Linux man pages

SYNOPSIS         top

       man [section] title

DESCRIPTION         top

       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 functions).

       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 inline.

   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).

       section
              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).

       manual-section
              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.

              NAME
              LIBRARY          [Normally only in Sections 2, 3]
              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]
              STANDARDS
              HISTORY
              NOTES
              CAVEATS
              BUGS
              EXAMPLES
              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.

       LIBRARY
              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]).

       SYNOPSIS
              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 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
              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 example).

       OPTIONS
              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.

       EXIT STATUS
              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.

       RETURN VALUE
              For Section 2 and 3 pages, this section gives a list of
              the values the library routine will return to the caller
              and the conditions that cause these values to be returned.

       ERRORS For Section 2 and 3 manual pages, this is a list of the
              values that may be placed in errno in the event of an
              error, along with information about the cause of the
              errors.

              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.

       ENVIRONMENT
              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.

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

       VERSIONS
              A summary of systems where the API performs differently,
              or where there's a similar API.

       STANDARDS
              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 standards(7).

              This section should note the current standards to which
              the API conforms to.

              If the API is not governed by any standards but commonly
              exists on other systems, note them.  If the call is Linux-
              specific or GNU-specific, note this.  If it's available in
              the BSDs, note that.

              If this section consists of just a list of standards
              (which it commonly does), terminate the list with a period
              ('.').

       HISTORY
              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
              HISTORY 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 2.0).

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

       Old versions of standards should be mentioned here, rather than
       in STANDARDS, for example, SUS, SUSv2, and XPG, or the SVr4 and
       4.xBSD implementation standards.

       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.

       CAVEATS
              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 activities.

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

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

       AUTHORS
              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.

       REPORTING BUGS
              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.

       COPYRIGHT
              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 ALSO.

       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.

FORMATTING AND WORDING CONVENTIONS         top

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

   SYNOPSIS
       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 .P) may be added in
       the following cases:

       •  to separate long lists of function prototypes into related
          groups (see for example list(3));

       •  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
            example:

                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);

   RETURN VALUE
       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.

   ATTRIBUTES
       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.

STYLE GUIDE         top

       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.

   Lists
       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 arrays.
              1      When it represents fields of a file, to be
                     consistent with tools like cut(1).

       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 .P 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., -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.

       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.

   Spelling
       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 for:

       •  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.

   Capitalization
       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
       .P or .IP).  For example:

           .P
           .in +4n
           .EX
           int
           main(int argc, char *argv[])
           {
               return 0;
           }
           .EE
           .in
           .P

   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
                            port
       real-time            realtime, real time
       run time             runtime
       saved set-group-ID   saved group ID, saved
                            set-GID
       saved set-user-ID    saved user ID, saved
                            set-UID
       set-group-ID         set-GID, setgid
       set-user-ID          set-UID, setuid
       superuser            super user, super-user
       superblock           super block, super-
                            block
       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
                                                     similar
       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, etc.
       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

   Trademarks
       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:

              DG/UX
              HP-UX
              UNIX
              UnixWare

   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 pointer".

       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".

   Hyperlinks
       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.

   Em-dashes
       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:

              interprocess
              multithreaded
              multiprocess
              nonblocking
              nondefault
              nonempty
              noninteractive
              nonnegative
              nonportable
              nonzero
              preallocated
              precreate
              prerecorded
              reestablished
              reinitialize
              rearm
              reread
              subcomponent
              subdirectory
              subsystem

       Hyphens  should  be  retained  when  the  prefixes  are  used  in
       nonstandard   English   words,  with  trademarks,  proper  nouns,
       acronyms, or compound terms.  Some examples:

              non-ASCII
              non-English
              non-NULL
              non-real-time

       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

           \[aq]C\[aq]

       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 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 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
          style:

              indent -npro -kr -i4 -ts4 -sob -l72 -ss -nut -psl prog.c

       •  For consistency, all example programs should terminate using
          either of:

              exit(EXIT_SUCCESS);
              exit(EXIT_FAILURE);

          Avoid using the following forms to terminate a program:

              exit(0);
              exit(1);
              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 feature:

       •  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).

EXAMPLES         top

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

SEE ALSO         top

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

COLOPHON         top

       This page is part of the man-pages (Linux kernel and C library
       user-space interface documentation) project.  Information about
       the project can be found at 
       ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report
       for this manual page, see
       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
       This page was obtained from the tarball man-pages-6.9.1.tar.gz
       fetched from
       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
       2024-06-26.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-
       to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not
       part of the original manual page), send a mail to
       [email protected]

Linux man-pages 6.9.1          2024-06-15                   man-pages(7)

Pages that refer to this page: intro(1)man(1)libc(7)