Provided by: mandoc_1.14.6-1_amd64 bug

NAME

       mdoc - semantic markup language for formatting manual pages

DESCRIPTION

       The mdoc language supports authoring of manual pages for the man(1) utility by allowing
       semantic annotations of words, phrases, page sections and complete manual pages.  Such
       annotations are used by formatting tools to achieve a uniform presentation across all
       manuals written in mdoc, and to support hyperlinking if supported by the output medium.

       This reference document describes the structure of manual pages and the syntax and usage
       of the mdoc language.  The reference implementation of a parsing and formatting tool is
       mandoc(1); the COMPATIBILITY section describes compatibility with other implementations.

       In an mdoc document, lines beginning with the control character ‘.’  are called “macro
       lines”.  The first word is the macro name.  It consists of two or three letters.  Most
       macro names begin with a capital letter.  For a list of available macros, see MACRO
       OVERVIEW.  The words following the macro name are arguments to the macro, optionally
       including the names of other, callable macros; see MACRO SYNTAX for details.

       Lines not beginning with the control character are called “text lines”.  They provide
       free-form text to be printed; the formatting of the text depends on the respective
       processing context:

             .Sh Macro lines change control state.
             Text lines are interpreted within the current state.

       Many aspects of the basic syntax of the mdoc language are based on the roff(7) language;
       see the LANGUAGE SYNTAX and MACRO SYNTAX sections in the roff(7) manual for details, in
       particular regarding comments, escape sequences, whitespace, and quoting.  However, using
       roff(7) requests in mdoc documents is discouraged; mandoc(1) supports some of them merely
       for backward compatibility.

MANUAL STRUCTURE

       A well-formed mdoc document consists of a document prologue followed by one or more
       sections.

       The prologue, which consists of the Dd, Dt, and Os macros in that order, is required for
       every document.

       The first section (sections are denoted by Sh) must be the NAME section, consisting of at
       least one Nm followed by Nd.

       Following that, convention dictates specifying at least the SYNOPSIS and DESCRIPTION
       sections, although this varies between manual sections.

       The following is a well-formed skeleton mdoc file for a utility "progname":

             .Dd $Mdocdate$
             .Dt PROGNAME section
             .Os
             .Sh NAME
             .Nm progname
             .Nd one line about what it does
             .\" .Sh LIBRARY
             .\" For sections 2, 3, and 9 only.
             .\" Not used in OpenBSD.
             .Sh SYNOPSIS
             .Nm progname
             .Op Fl options
             .Ar
             .Sh DESCRIPTION
             The
             .Nm
             utility processes files ...
             .\" .Sh CONTEXT
             .\" For section 9 functions only.
             .\" .Sh IMPLEMENTATION NOTES
             .\" Not used in OpenBSD.
             .\" .Sh RETURN VALUES
             .\" For sections 2, 3, and 9 function return values only.
             .\" .Sh ENVIRONMENT
             .\" For sections 1, 6, 7, and 8 only.
             .\" .Sh FILES
             .\" .Sh EXIT STATUS
             .\" For sections 1, 6, and 8 only.
             .\" .Sh EXAMPLES
             .\" .Sh DIAGNOSTICS
             .\" For sections 1, 4, 6, 7, 8, and 9 printf/stderr messages only.
             .\" .Sh ERRORS
             .\" For sections 2, 3, 4, and 9 errno settings only.
             .\" .Sh SEE ALSO
             .\" .Xr foobar 1
             .\" .Sh STANDARDS
             .\" .Sh HISTORY
             .\" .Sh AUTHORS
             .\" .Sh CAVEATS
             .\" .Sh BUGS
             .\" .Sh SECURITY CONSIDERATIONS
             .\" Not used in OpenBSD.

       The sections in an mdoc document are conventionally ordered as they appear above.
       Sections should be composed as follows:

             NAME
             The name(s) and a one line description of the documented material.  The syntax for
             this as follows:

                   .Nm name0 ,
                   .Nm name1 ,
                   .Nm name2
                   .Nd a one line description

             Multiple ‘Nm’ names should be separated by commas.

             The Nm macro(s) must precede the Nd macro.

             See Nm and Nd.

             LIBRARY
             The name of the library containing the documented material, which is assumed to be a
             function in a section 2, 3, or 9 manual.  The syntax for this is as follows:

                   .Lb libarm

             See Lb.

             SYNOPSIS
             Documents the utility invocation syntax, function call syntax, or device
             configuration.

             For the first, utilities (sections 1, 6, and 8), this is generally structured as
             follows:

                   .Nm bar
                   .Op Fl v
                   .Op Fl o Ar file
                   .Op Ar
                   .Nm foo
                   .Op Fl v
                   .Op Fl o Ar file
                   .Op Ar

             Commands should be ordered alphabetically.

             For the second, function calls (sections 2, 3, 9):

                   .In header.h
                   .Vt extern const char *global;
                   .Ft "char *"
                   .Fn foo "const char *src"
                   .Ft "char *"
                   .Fn bar "const char *src"

             Ordering of In, Vt, Fn, and Fo macros should follow C header-file conventions.

             And for the third, configurations (section 4):

                   .Cd "it* at isa? port 0x2e"
                   .Cd "it* at isa? port 0x4e"

             Manuals not in these sections generally don't need a SYNOPSIS.

             Some macros are displayed differently in the SYNOPSIS section, particularly Nm, Cd,
             Fd, Fn, Fo, In, Vt, and Ft.  All of these macros are output on their own line.  If
             two such dissimilar macros are pairwise invoked (except for Ft before Fo or Fn),
             they are separated by a vertical space, unless in the case of Fo, Fn, and Ft, which
             are always separated by vertical space.

             When text and macros following an Nm macro starting an input line span multiple
             output lines, all output lines but the first will be indented to align with the text
             immediately following the Nm macro, up to the next Nm, Sh, or Ss macro or the end of
             an enclosing block, whichever comes first.

             DESCRIPTION
             This begins with an expansion of the brief, one line description in NAME:

                   The
                   .Nm
                   utility does this, that, and the other.

             It usually follows with a breakdown of the options (if documenting a command), such
             as:

                   The options are as follows:
                   .Bl -tag -width Ds
                   .It Fl v
                   Print verbose information.
                   .El

             List the options in alphabetical order, uppercase before lowercase for each letter
             and with no regard to whether an option takes an argument.  Put digits in ascending
             order before all letter options.

             Manuals not documenting a command won't include the above fragment.

             Since the DESCRIPTION section usually contains most of the text of a manual, longer
             manuals often use the Ss macro to form subsections.  In very long manuals, the
             DESCRIPTION may be split into multiple sections, each started by an Sh macro
             followed by a non-standard section name, and each having several subsections, like
             in the present mdoc manual.

             CONTEXT
             This section lists the contexts in which functions can be called in section 9.  The
             contexts are autoconf, process, or interrupt.

             IMPLEMENTATION NOTES
             Implementation-specific notes should be kept here.  This is useful when implementing
             standard functions that may have side effects or notable algorithmic implications.

             RETURN VALUES
             This section documents the return values of functions in sections 2, 3, and 9.

             See Rv.

             ENVIRONMENT
             Lists the environment variables used by the utility, and explains the syntax and
             semantics of their values.  The environ(7) manual provides examples of typical
             content and formatting.

             See Ev.

             FILES
             Documents files used.  It's helpful to document both the file name and a short
             description of how the file is used (created, modified, etc.).

             See Pa.

             EXIT STATUS
             This section documents the command exit status for section 1, 6, and 8 utilities.
             Historically, this information was described in DIAGNOSTICS, a practise that is now
             discouraged.

             See Ex.

             EXAMPLES
             Example usages.  This often contains snippets of well-formed, well-tested
             invocations.  Make sure that examples work properly!

             DIAGNOSTICS
             Documents error messages.  In section 4 and 9 manuals, these are usually messages
             printed by the kernel to the console and to the kernel log.  In section 1, 6, 7, and
             8, these are usually messages printed by userland programs to the standard error
             output.

             Historically, this section was used in place of EXIT STATUS for manuals in sections
             1, 6, and 8; however, this practise is discouraged.

             See Bl -diag.

             ERRORS
             Documents errno(2) settings in sections 2, 3, 4, and 9.

             See Er.

             SEE ALSO
             References other manuals with related topics.  This section should exist for most
             manuals.  Cross-references should conventionally be ordered first by section, then
             alphabetically (ignoring case).

             References to other documentation concerning the topic of the manual page, for
             example authoritative books or journal articles, may also be provided in this
             section.

             See Rs and Xr.

             STANDARDS
             References any standards implemented or used.  If not adhering to any standards, the
             HISTORY section should be used instead.

             See St.

             HISTORY
             A brief history of the subject, including where it was first implemented, and when
             it was ported to or reimplemented for the operating system at hand.

             AUTHORS
             Credits to the person or persons who wrote the code and/or documentation.  Authors
             should generally be noted by both name and email address.

             See An.

             CAVEATS
             Common misuses and misunderstandings should be explained in this section.

             BUGS
             Known bugs, limitations, and work-arounds should be described in this section.

             SECURITY CONSIDERATIONS
             Documents any security precautions that operators should consider.

MACRO OVERVIEW

       This overview is sorted such that macros of similar purpose are listed together, to help
       find the best macro for any given purpose.  Deprecated macros are not included in the
       overview, but can be found below in the alphabetical MACRO REFERENCE.

   Document preamble and NAME section macros
              Dd   document date: $Mdocdate$ | month day, year

              Dt   document title: TITLE section [arch]

              Os   operating system version: [system [version]]

              Nm   document name (one argument)

              Nd   document description (one line)

   Sections and cross references
              Sh   section header (one line)

              Ss   subsection header (one line)

              Sx   internal cross reference to a section or subsection

              Xr   cross reference to another manual page: name section

              Tg   tag the definition of a term (<= 1 arguments)

              Pp   start a text paragraph (no arguments)

   Displays and lists
              Bd, Ed            display block:
       -type
       [-offset width]
       [-compact]

              D1                indented display (one line)

              Dl                indented literal display (one line)

              Ql                in-line literal display: ‘text’

              Bl, El            list block:
       -type
       [-width val]
       [-offset val]

       [-compact]

              It                list item (syntax depends on -type)

              Ta                table cell separator in Bl -column lists

              Rs, %*, Re        bibliographic block (references)

   Spacing control
              Pf       prefix, no following horizontal space (one argument)

              Ns       roman font, no preceding horizontal space (no arguments)

              Ap       apostrophe without surrounding whitespace (no arguments)

              Sm       switch horizontal spacing mode: [on | off]

              Bk, Ek   keep block: -words

   Semantic markup for command line utilities
              Nm           start a SYNOPSIS block with the name of a utility

              Fl           command line options (flags) (>=0 arguments)

              Cm           command modifier (>0 arguments)

              Ar           command arguments (>=0 arguments)

              Op, Oo, Oc   optional syntax elements (enclosure)

              Ic           internal or interactive command (>0 arguments)

              Ev           environmental variable (>0 arguments)

              Pa           file system path (>=0 arguments)

   Semantic markup for function libraries
              Lb       function library (one argument)

              In       include file (one argument)

              Fd       other preprocessor directive (>0 arguments)

              Ft       function type (>0 arguments)

              Fo, Fc   function block: funcname

              Fn       function name: funcname [argument ...]

              Fa       function argument (>0 arguments)

              Vt       variable type (>0 arguments)

              Va       variable name (>0 arguments)

              Dv       defined variable or preprocessor constant (>0 arguments)

              Er       error constant (>0 arguments)

              Ev       environmental variable (>0 arguments)

   Various semantic markup
              An   author name (>0 arguments)

              Lk   hyperlink: uri [display_name]

              Mt   “mailto” hyperlink: localpart@domain

              Cd   kernel configuration declaration (>0 arguments)

              Ad   memory address (>0 arguments)

              Ms   mathematical symbol (>0 arguments)

   Physical markup
              Em       italic font or underline (emphasis) (>0 arguments)

              Sy       boldface font (symbolic) (>0 arguments)

              No       return to roman font (normal) (>0 arguments)

              Bf, Ef   font block: -type | Em | Li | Sy

   Physical enclosures
              Dq, Do, Dc      enclose in typographic double quotes: “text”

              Qq, Qo, Qc      enclose in typewriter double quotes: "text"

              Sq, So, Sc      enclose in single quotes: ‘text’

              Pq, Po, Pc      enclose in parentheses: (text)

              Bq, Bo, Bc      enclose in square brackets: [text]

              Brq, Bro, Brc   enclose in curly braces: {text}

              Aq, Ao, Ac      enclose in angle brackets: ⟨text⟩

              Eo, Ec          generic enclosure

   Text production
              Ex -std   standard command exit values: [utility ...]

              Rv -std   standard function return values: [function ...]

              St        reference to a standards document (one argument)

              At        AT&T UNIX

              Bx        BSD

              Bsx       BSD/OS

              Nx        NetBSD

              Fx        FreeBSD

              Ox        OpenBSD

              Dx        DragonFly

MACRO REFERENCE

       This section is a canonical reference of all macros, arranged alphabetically.  For the
       scoping of individual macros, see MACRO SYNTAX.

       %A first_name ... last_name
            Author name of an Rs block.  Multiple authors should each be accorded their own %A
            line.  Author names should be ordered with full or abbreviated forename(s) first,
            then full surname.

       %B title
            Book title of an Rs block.  This macro may also be used in a non-bibliographic
            context when referring to book titles.

       %C location
            Publication city or location of an Rs block.

       %D [month day,] year
            Publication date of an Rs block.  Provide the full English name of the month and all
            four digits of the year.

       %I name
            Publisher or issuer name of an Rs block.

       %J name
            Journal name of an Rs block.

       %N number
            Issue number (usually for journals) of an Rs block.

       %O line
            Optional information of an Rs block.

       %P number
            Book or journal page number of an Rs block.  Conventionally, the argument starts with
            ‘p.’ for a single page or ‘pp.’ for a range of pages, for example:

                  .%P pp. 42\(en47

       %Q name
            Institutional author (school, government, etc.) of an Rs block.  Multiple
            institutional authors should each be accorded their own %Q line.

       %R name
            Technical report name of an Rs block.

       %T title
            Article title of an Rs block.  This macro may also be used in a non-bibliographical
            context when referring to article titles.

       %U protocol://path
            URI of reference document.

       %V number
            Volume number of an Rs block.

       Ac
            Close an Ao block.  Does not have any tail arguments.

       Ad address
            Memory address.  Do not use this for postal addresses.

            Examples:
                  .Ad [0,$]
                       .Ad 0x00000000

       An -split | -nosplit | first_name ... last_name
            Author name.  Can be used both for the authors of the program, function, or driver
            documented in the manual, or for the authors of the manual itself.  Requires either
            the name of an author or one of the following arguments:

                  -split     Start a new output line before each subsequent invocation of An.
                  -nosplit   The opposite of -split.

            The default is -nosplit.  The effect of selecting either of the -split modes ends at
            the beginning of the AUTHORS section.  In the AUTHORS section, the default is
            -nosplit for the first author listing and -split for all other author listings.

            Examples:
                       .An -nosplit
                       .An Kristaps Dzonsons Aq Mt kristaps@bsd.lv

       Ao block
            Begin a block enclosed by angle brackets.  Does not have any head arguments.  This
            macro is almost never useful.  See Aq for more details.

       Ap
            Inserts an apostrophe without any surrounding whitespace.  This is generally used as
            a grammatical device when referring to the verb form of a function.

            Examples:
                  .Fn execve Ap d

       Aq line
            Enclose the rest of the input line in angle brackets.  The only important use case is
            for email addresses.  See Mt for an example.

            Occasionally, it is used for names of characters and keys, for example:

                  Press the
                  .Aq escape
                  key to ...

            For URIs, use Lk instead, and In for “#include” directives.  Never wrap Ar in Aq.

            Since Aq usually renders with non-ASCII characters in non-ASCII output modes, do not
            use it where the ASCII characters ‘<’ and ‘>’ are required as syntax elements.
            Instead, use these characters directly in such cases, combining them with the macros
            Pf, Ns, or Eo as needed.

            See also Ao.

       Ar [placeholder ...]
            Command arguments.  If an argument is not provided, the string “file ...” is used as
            a default.

            Examples:
                  .Fl o Ar file
                       .Ar
                       .Ar arg1 , arg2 .

            The arguments to the Ar macro are names and placeholders for command arguments; for
            fixed strings to be passed verbatim as arguments, use Fl or Cm.

       At [version]
            Formats an AT&T UNIX version.  Accepts one optional argument:

                  v[1-7] | 32v   A version of AT&T UNIX.
                  III            AT&T System III UNIX.
                  V | V.[1-4]    A version of AT&T System V UNIX.

            Note that these arguments do not begin with a hyphen.

            Examples:
                       .At
                       .At III
                       .At V.1

            See also Bsx, Bx, Dx, Fx, Nx, and Ox.

       Bc
            Close a Bo block.  Does not have any tail arguments.

       Bd -type [-offset width] [-compact]
            Begin a display block.  Display blocks are used to select a different indentation and
            justification than the one used by the surrounding text.  They may contain both macro
            lines and text lines.  By default, a display block is preceded by a vertical space.

            The type must be one of the following:

                  -centered      Produce one output line from each input line, and center-justify
                                 each line.  Using this display type is not recommended; many
                                 mdoc implementations render it poorly.

                  -filled        Change the positions of line breaks to fill each line, and left-
                                 and right-justify the resulting block.

                  -literal       Produce one output line from each input line, and do not justify
                                 the block at all.  Preserve white space as it appears in the
                                 input.  Always use a constant-width font.  Use this for
                                 displaying source code.

                  -ragged        Change the positions of line breaks to fill each line, and left-
                                 justify the resulting block.

                  -unfilled      The same as -literal, but using the same font as for normal
                                 text, which is a variable width font if supported by the output
                                 device.

            The type must be provided first.  Additional arguments may follow:

                       -offset width
                                      Indent the display by the width, which may be one of the
                                      following:

                       One of the pre-defined strings indent, the width of a standard indentation
                       (six constant width characters); indent-two, twice indent; left, which has
                       no effect; right, which justifies to the right margin; or center, which
                       aligns around an imagined center axis.

                       A macro invocation, which selects a predefined width associated with that
                       macro.  The most popular is the imaginary macro Ds, which resolves to 6n.

                       A scaling width as described in roff(7).

                       An arbitrary string, which indents by the length of this string.
                                      When the argument is missing, -offset is ignored.

                       -compact       Do not assert vertical space before the display.

            Examples:

                       .Bd -literal -offset indent -compact
                          Hello       world.
                       .Ed

            See also D1 and Dl.

       Bf -emphasis | -literal | -symbolic | Em | Li | Sy
            Change the font mode for a scoped block of text.  The -emphasis and Em argument are
            equivalent, as are -symbolic and Sy, and -literal and Li.  Without an argument, this
            macro does nothing.  The font mode continues until broken by a new font mode in a
            nested scope or Ef is encountered.

            See also Li, Ef, Em, and Sy.

       Bk -words
            For each macro, keep its output together on the same output line, until the end of
            the macro or the end of the input line is reached, whichever comes first.  Line
            breaks in text lines are unaffected.

            The -words argument is required; additional arguments are ignored.

            The following example will not break within each Op macro line:

                  .Bk -words
                  .Op Fl f Ar flags
                  .Op Fl o Ar output
                  .Ek

            Be careful in using over-long lines within a keep block!  Doing so will clobber the
            right margin.

       Bl
            -type [-width val] [-offset val] [-compact] [col ...]  Begin a list.  Lists consist
            of items specified using the It macro, containing a head or a body or both.

            The list type is mandatory and must be specified first.  The -width and -offset
            arguments accept macro names as described for Bd -offset, scaling widths as described
            in roff(7), or use the length of the given string.  The -offset is a global
            indentation for the whole list, affecting both item heads and bodies.  For those list
            types supporting it, the -width argument requests an additional indentation of item
            bodies, to be added to the -offset.  Unless the -compact argument is specified, list
            entries are separated by vertical space.

            A list must specify one of the following list types:

                  -bullet       No item heads can be specified, but a bullet will be printed at
                                the head of each item.  Item bodies start on the same output line
                                as the bullet and are indented according to the -width argument.

                  -column       A columnated list.  The -width argument has no effect; instead,
                                the string length of each argument specifies the width of one
                                column.  If the first line of the body of a -column list is not
                                an It macro line, It contexts spanning one input line each are
                                implied until an It macro line is encountered, at which point
                                items start being interpreted as described in the It
                                documentation.

                  -dash         Like -bullet, except that dashes are used in place of bullets.

                  -diag         Like -inset, except that item heads are not parsed for macro
                                invocations.  Most often used in the DIAGNOSTICS section with
                                error constants in the item heads.

                  -enum         A numbered list.  No item heads can be specified.  Formatted like
                                -bullet, except that cardinal numbers are used in place of
                                bullets, starting at 1.

                  -hang         Like -tag, except that the first lines of item bodies are not
                                indented, but follow the item heads like in -inset lists.

                  -hyphen       Synonym for -dash.

                  -inset        Item bodies follow items heads on the same line, using normal
                                inter-word spacing.  Bodies are not indented, and the -width
                                argument is ignored.

                  -item         No item heads can be specified, and none are printed.  Bodies are
                                not indented, and the -width argument is ignored.

                  -ohang        Item bodies start on the line following item heads and are not
                                indented.  The -width argument is ignored.

                  -tag          Item bodies are indented according to the -width argument.  When
                                an item head fits inside the indentation, the item body follows
                                this head on the same output line.  Otherwise, the body starts on
                                the output line following the head.

            Lists may be nested within lists and displays.  Nesting of -column and -enum lists
            may not be portable.

            See also El and It.

       Bo block
            Begin a block enclosed by square brackets.  Does not have any head arguments.

            Examples:
                  .Bo 1 ,
                  .Dv BUFSIZ Bc

            See also Bq.

       Bq line
            Encloses its arguments in square brackets.

            Examples:
                  .Bq 1, Dv BUFSIZ

            Remarks: this macro is sometimes abused to emulate optional arguments for commands;
            the correct macros to use for this purpose are Op, Oo, and Oc.

            See also Bo.

       Brc  Close a Bro block.  Does not have any tail arguments.

       Bro block
            Begin a block enclosed by curly braces.  Does not have any head arguments.

            Examples:
                  .Bro 1 , ... ,
                  .Va n Brc

            See also Brq.

       Brq line
            Encloses its arguments in curly braces.

            Examples:
                  .Brq 1, ..., Va n

            See also Bro.

       Bsx [version]
            Format the BSD/OS version provided as an argument, or a default value if no argument
            is provided.

            Examples:
                  .Bsx 1.0
                       .Bsx

            See also At, Bx, Dx, Fx, Nx, and Ox.

       Bt
            Supported only for compatibility, do not use this in new manuals.  Prints “is
            currently in beta test.”

       Bx [version [variant]]
            Format the BSD version provided as an argument, or a default value if no argument is
            provided.

            Examples:
                  .Bx 4.3 Tahoe
                       .Bx 4.4
                       .Bx

            See also At, Bsx, Dx, Fx, Nx, and Ox.

       Cd line
            Kernel configuration declaration.  This denotes strings accepted by config(8).  It is
            most often used in section 4 manual pages.

            Examples:
                  .Cd device le0 at scode?

            Remarks: this macro is commonly abused by using quoted literals to retain whitespace
            and align consecutive Cd declarations.  This practise is discouraged.

       Cm keyword ...
            Command modifiers.  Typically used for fixed strings passed as arguments to
            interactive commands, to commands in interpreted scripts, or to configuration file
            directives, unless Fl is more appropriate.

            Examples:
                  .Nm mt Fl f Ar device Cm rewind
                       .Nm ps Fl o Cm pid , Ns Cm command
                       .Nm dd Cm if= Ns Ar file1 Cm of= Ns Ar file2
                       .Ic set Fl o Cm vi
                       .Ic lookup Cm file bind
                       .Ic permit Ar identity Op Cm as Ar target

       D1 line
            One-line indented display.  This is formatted by the default rules and is useful for
            simple indented statements.  It is followed by a newline.

            Examples:
                  .D1 Fl abcdefgh

            See also Bd and Dl.

       Db
            This macro is obsolete.  No replacement is needed.  It is ignored by mandoc(1) and
            groff including its arguments.  It was formerly used to toggle a debugging mode.

       Dc
            Close a Do block.  Does not have any tail arguments.

       Dd $Mdocdate$ | month day, year
            Document date for display in the page footer, by convention the date of the last
            change.  This is the mandatory first macro of any mdoc manual.

            The month is the full English month name, the day is an integer number, and the year
            is the full four-digit year.

            Other arguments are not portable; the mandoc(1) utility handles them as follows:
               -   To have the date automatically filled in by the OpenBSD version of cvs(1), the
                   special string “$Mdocdate$” can be given as an argument.
               -   The traditional, purely numeric man(7) format yearmonthday is accepted, too.
               -   If a date string cannot be parsed, it is used verbatim.
               -   If no date string is given, the current date is used.

            Examples:
                       .Dd $Mdocdate$
                       .Dd $Mdocdate: July 2 2018$
                       .Dd July 2, 2018

            See also Dt and Os.

       Dl line
            One-line indented display.  This is formatted as literal text and is useful for
            commands and invocations.  It is followed by a newline.

            Examples:
                  .Dl % mandoc mdoc.7 \(ba less

            See also Ql, Bd -literal, and D1.

       Do block
            Begin a block enclosed by double quotes.  Does not have any head arguments.

            Examples:
                  .Do
                  April is the cruellest month
                  .Dc
                  \(em T.S. Eliot

            See also Dq.

       Dq line
            Encloses its arguments in “typographic” double-quotes.

            Examples:
                  .Dq April is the cruellest month
                  \(em T.S. Eliot

            See also Qq, Sq, and Do.

       Dt TITLE section [arch]
            Document title for display in the page header.  This is the mandatory second macro of
            any mdoc file.

            Its arguments are as follows:

              TITLE    The document's title (name), defaulting to “UNTITLED” if unspecified.  To
                       achieve a uniform appearance of page header lines, it should by convention
                       be all caps.

              section  The manual section.  This may be one of 1 (General Commands), 2 (System
                       Calls), 3 (Library Functions), 3p (Perl Library), 4 (Device Drivers), 5
                       (File Formats), 6 (Games), 7 (Miscellaneous Information), 8 (System
                       Manager's Manual), or 9 (Kernel Developer's Manual).  It should correspond
                       to the manual's filename suffix and defaults to the empty string if
                       unspecified.

              arch     This specifies the machine architecture a manual page applies to, where
                       relevant, for example alpha, amd64, i386, or sparc64.  The list of valid
                       architectures varies by operating system.

            Examples:
                       .Dt FOO 1
                       .Dt FOO 9 i386

            See also Dd and Os.

       Dv identifier ...
            Defined variables such as preprocessor constants, constant symbols, enumeration
            values, and so on.

            Examples:
                  .Dv NULL
                       .Dv BUFSIZ
                       .Dv STDOUT_FILENO

            See also Er and Ev for special-purpose constants, Va for variable symbols, and Fd for
            listing preprocessor variable definitions in the SYNOPSIS.

       Dx [version]
            Format the DragonFly version provided as an argument, or a default value if no
            argument is provided.

            Examples:
                  .Dx 2.4.1
                       .Dx

            See also At, Bsx, Bx, Fx, Nx, and Ox.

       Ec [closing_delimiter]
            Close a scope started by Eo.

            The closing_delimiter argument is used as the enclosure tail, for example, specifying
            \(rq will emulate Dc.

       Ed
            End a display context started by Bd.

       Ef
            End a font mode context started by Bf.

       Ek
            End a keep context started by Bk.

       El
            End a list context started by Bl.  See also It.

       Em word ...
            Request an italic font.  If the output device does not provide that, underline.

            This is most often used for stress emphasis (not to be confused with importance, see
            Sy).  In the rare cases where none of the semantic markup macros fit, it can also be
            used for technical terms and placeholders, except that for syntax elements, Sy and Ar
            are preferred, respectively.

            Examples:
                  Selected lines are those
                  .Em not
                  matching any of the specified patterns.
                  Some of the functions use a
                  .Em hold space
                  to save the pattern space for subsequent retrieval.

            See also No, Ql, and Sy.

       En word ...
            This macro is obsolete.  Use Eo or any of the other enclosure macros.

            It encloses its argument in the delimiters specified by the last Es macro.

       Eo [opening_delimiter]
            An arbitrary enclosure.  The opening_delimiter argument is used as the enclosure
            head, for example, specifying \(lq will emulate Do.

       Er identifier ...
            Error constants for definitions of the errno libc global variable.  This is most
            often used in section 2 and 3 manual pages.

            Examples:
                  .Er EPERM
                       .Er ENOENT

            See also Dv for general constants.

       Es opening_delimiter closing_delimiter
            This macro is obsolete.  Use Eo or any of the other enclosure macros.

            It takes two arguments, defining the delimiters to be used by subsequent En macros.

       Ev identifier ...
            Environmental variables such as those specified in environ(7).

            Examples:
                  .Ev DISPLAY
                       .Ev PATH

            See also Dv for general constants.

       Ex -std [utility ...]
            Insert a standard sentence regarding command exit values of 0 on success and >0 on
            failure.  This is most often used in section 1, 6, and 8 manual pages.

            If utility is not specified, the document's name set by Nm is used.  Multiple utility
            arguments are treated as separate utilities.

            See also Rv.

       Fa argument ...
            Function argument or parameter.  Each argument may be a name and a type (recommended
            for the SYNOPSIS section), a name alone (for function invocations), or a type alone
            (for function prototypes).  If both a type and a name are given or if the type
            consists of multiple words, all words belonging to the same function argument have to
            be given in a single argument to the Fa macro.

            This macro is also used to specify the field name of a structure.

            Most often, the Fa macro is used in the SYNOPSIS within Fo blocks when documenting
            multi-line function prototypes.  If invoked with multiple arguments, the arguments
            are separated by a comma.  Furthermore, if the following macro is another Fa, the
            last argument will also have a trailing comma.

            Examples:
                  .Fa "const char *p"
                       .Fa "int a" "int b" "int c"
                       .Fa "char *" size_t

            See also Fo.

       Fc
            End a function context started by Fo.

       Fd #directive [argument ...]
            Preprocessor directive, in particular for listing it in the SYNOPSIS.  Historically,
            it was also used to document include files.  The latter usage has been deprecated in
            favour of In.

            Examples:
                  .Fd #define sa_handler __sigaction_u.__sa_handler
                       .Fd #define SIO_MAXNFDS
                       .Fd #ifdef FS_DEBUG
                       .Ft void
                       .Fn dbg_open "const char *"
                       .Fd #endif

            See also MANUAL STRUCTURE, In, and Dv.

       Fl [word ...]
            Command-line flag or option.  Used when listing arguments to command-line utilities.
            For each argument, prints an ASCII hyphen-minus character ‘-’, immediately followed
            by the argument.  If no arguments are provided, a hyphen-minus is printed followed by
            a space.  If the argument is a macro, a hyphen-minus is prefixed to the subsequent
            macro output.

            Examples:
                  .Nm du Op Fl H | L | P
                       .Nm ls Op Fl 1AaCcdFfgHhikLlmnopqRrSsTtux
                       .Nm route Cm add Fl inet Ar destination gateway
                       .Nm locate.updatedb Op Fl \-fcodes Ns = Ns Ar dbfile
                       .Nm aucat Fl o Fl
                       .Nm kill Fl Ar signal_number

            For GNU-sytle long options, escaping the additional hyphen-minus is not strictly
            required, but may be safer with future versions of GNU troff; see mandoc_char(7) for
            details.

            See also Cm.

       Fn funcname [argument ...]
            A function name.

            Function arguments are surrounded in parenthesis and are delimited by commas.  If no
            arguments are specified, blank parenthesis are output.  In the SYNOPSIS section, this
            macro starts a new output line, and a blank line is automatically inserted between
            function definitions.

            Examples:
                  .Fn "int funcname" "int arg0" "int arg1"
                       .Fn funcname "int arg0"
                       .Fn funcname arg0

                       .Ft functype
                       .Fn funcname

            When referring to a function documented in another manual page, use Xr instead.  See
            also MANUAL STRUCTURE, Fo, and Ft.

       Fo funcname
            Begin a function block.  This is a multi-line version of Fn.

            Invocations usually occur in the following context:

                  ...

            A Fo scope is closed by Fc.

            See also MANUAL STRUCTURE, Fa, Fc, and Ft.

       Fr number
            This macro is obsolete.  No replacement markup is needed.

            It was used to show numerical function return values in an italic font.

       Ft functype
            A function type.

            In the SYNOPSIS section, a new output line is started after this macro.

            Examples:
                  .Ft int
                       .Ft functype
                       .Fn funcname

            See also MANUAL STRUCTURE, Fn, and Fo.

       Fx [version]
            Format the FreeBSD version provided as an argument, or a default value if no argument
            is provided.

            Examples:
                  .Fx 7.1
                       .Fx

            See also At, Bsx, Bx, Dx, Nx, and Ox.

       Hf filename
            This macro is not implemented in mandoc(1).  It was used to include the contents of a
            (header) file literally.

       Ic keyword ...
            Internal or interactive command, or configuration instruction in a configuration
            file.  See also Cm.

            Examples:
                  .Ic :wq
                       .Ic hash
                       .Ic alias

            Note that using Ql, Dl, or Bd -literal is preferred for displaying code samples; the
            Ic macro is used when referring to an individual command name.

       In filename
            The name of an include file.  This macro is most often used in section 2, 3, and 9
            manual pages.

            When invoked as the first macro on an input line in the SYNOPSIS section, the
            argument is displayed in angle brackets and preceded by "#include", and a blank line
            is inserted in front if there is a preceding function declaration.  In other
            sections, it only encloses its argument in angle brackets and causes no line break.

            Examples:
                  .In sys/types.h

            See also MANUAL STRUCTURE.

       It [head]
            A list item.  The syntax of this macro depends on the list type.

            Lists of type -hang, -ohang, -inset, and -diag have the following syntax:

            Lists of type -bullet, -dash, -enum, -hyphen and -item have the following syntax:

            with subsequent lines interpreted within the scope of the It until either a closing
            El or another It.

            The -tag list has the following syntax:

            Subsequent lines are interpreted as with -bullet and family.  The line arguments
            correspond to the list's left-hand side; body arguments correspond to the list's
            contents.

            The -column list is the most complicated.  Its syntax is as follows:

            The arguments consist of one or more lines of text and macros representing a complete
            table line.  Cells within the line are delimited by the special Ta block macro or by
            literal tab characters.

            Using literal tabs is strongly discouraged because they are very hard to use
            correctly and mdoc code using them is very hard to read.  In particular, a blank
            character is syntactically significant before and after the literal tab character.
            If a word precedes or follows the tab without an intervening blank, that word is
            never interpreted as a macro call, but always output literally.

            The tab cell delimiter may only be used within the It line itself; on following
            lines, only the Ta macro can be used to delimit cells, and portability requires that
            Ta is called by other macros: some parsers do not recognize it when it appears as the
            first macro on a line.

            Note that quoted strings may span tab-delimited cells on an It line.  For example,

                       .It "col1 , <TAB> col2 ," ;

            will preserve the whitespace before both commas, but not the whitespace before the
            semicolon.

            See also Bl.

       Lb libname
            Specify a library.

            The name parameter may be a system library, such as z or pam, in which case a small
            library description is printed next to the linker invocation; or a custom library, in
            which case the library name is printed in quotes.  This is most commonly used in the
            SYNOPSIS section as described in MANUAL STRUCTURE.

            Examples:
                  .Lb libz
                       .Lb libmandoc

       Li word ...
            Request a typewriter (literal) font.  Deprecated because on terminal output devices,
            this is usually indistinguishable from normal text.  For literal displays, use Ql
            (in-line), Dl (single line), or Bd -literal (multi-line) instead.

       Lk uri [display_name]
            Format a hyperlink.

            Examples:
                  .Lk https://bsd.lv "The BSD.lv Project"
                       .Lk https://bsd.lv

            See also Mt.

       Lp
            Deprecated synonym for Pp.

       Ms name
            Display a mathematical symbol.

            Examples:
                  .Ms sigma
                       .Ms aleph

       Mt localpart@domain
            Format a “mailto:” hyperlink.

            Examples:
                  .Mt discuss@manpages.bsd.lv
                       .An Kristaps Dzonsons Aq Mt kristaps@bsd.lv

       Nd line
            A one line description of the manual's content.  This is the mandatory last macro of
            the NAME section and not appropriate for other sections.

            Examples:
                  .Nd mdoc language reference
                       .Nd format and display UNIX manuals

            The Nd macro technically accepts child macros and terminates with a subsequent Sh
            invocation.  Do not assume this behaviour: some whatis(1) database generators are not
            smart enough to parse more than the line arguments and will display macros verbatim.

            See also Nm.

       Nm [name]
            The name of the manual page, or — in particular in section 1, 6, and 8 pages — of an
            additional command or feature documented in the manual page.  When first invoked, the
            Nm macro expects a single argument, the name of the manual page.  Usually, the first
            invocation happens in the NAME section of the page.  The specified name will be
            remembered and used whenever the macro is called again without arguments later in the
            page.  The Nm macro uses Block full-implicit semantics when invoked as the first
            macro on an input line in the SYNOPSIS section; otherwise, it uses ordinary In-line
            semantics.

            Examples:

                  .Sh SYNOPSIS
                  .Nm cat
                  .Op Fl benstuv
                  .Op Ar

            In the SYNOPSIS of section 2, 3 and 9 manual pages, use the Fn macro rather than Nm
            to mark up the name of the manual page.

       No word ...
            Normal text.  Closes the scope of any preceding in-line macro.  When used after
            physical formatting macros like Em or Sy, switches back to the standard font face and
            weight.  Can also be used to embed plain text strings in macro lines using semantic
            annotation macros.

            Examples:
                  .Em italic , Sy bold , No and roman

                       .Sm off
                       .Cm :C No / Ar pattern No / Ar replacement No /
                       .Sm on

            See also Em, Ql, and Sy.

       Ns
            Suppress a space between the output of the preceding macro and the following text or
            macro.  Following invocation, input is interpreted as normal text just like after an
            No macro.

            This has no effect when invoked at the start of a macro line.

            Examples:
                  .Ar name Ns = Ns Ar value
                       .Cm :M Ns Ar pattern
                       .Fl o Ns Ar output

            See also No and Sm.

       Nx [version]
            Format the NetBSD version provided as an argument, or a default value if no argument
            is provided.

            Examples:
                  .Nx 5.01
                       .Nx

            See also At, Bsx, Bx, Dx, Fx, and Ox.

       Oc
            Close multi-line Oo context.

       Oo block
            Multi-line version of Op.

            Examples:
                  .Oo
                  .Op Fl flag Ns Ar value
                  .Oc

       Op line
            Optional part of a command line.  Prints the argument(s) in brackets.  This is most
            often used in the SYNOPSIS section of section 1 and 8 manual pages.

            Examples:
                  .Op Fl a Ar b
                       .Op Ar a | b

            See also Oo.

       Os [system [version]]
            Operating system version for display in the page footer.  This is the mandatory third
            macro of any mdoc file.

            The optional system parameter specifies the relevant operating system or environment.
            It is suggested to leave it unspecified, in which case mandoc(1) uses its -Ios
            argument or, if that isn't specified either, sysname and release as returned by
            uname(3).

            Examples:
                  .Os
                       .Os KTH/CSC/TCS
                       .Os BSD 4.3

            See also Dd and Dt.

       Ot functype
            This macro is obsolete.  Use Ft instead; with mandoc(1), both have the same effect.

            Historical mdoc packages described it as “old function type (FORTRAN)”.

       Ox [version]
            Format the OpenBSD version provided as an argument, or a default value if no argument
            is provided.

            Examples:
                  .Ox 4.5
                       .Ox

            See also At, Bsx, Bx, Dx, Fx, and Nx.

       Pa name ...
            An absolute or relative file system path, or a file or directory name.  If an
            argument is not provided, the character ‘~’ is used as a default.

            Examples:
                  .Pa /usr/bin/mandoc
                       .Pa /usr/share/man/man7/mdoc.7

            See also Lk.

       Pc
            Close parenthesised context opened by Po.

       Pf prefix macro [argument ...]
            Removes the space between its argument and the following macro.  It is equivalent to:

                  No \&prefix Ns macro [argument ...]

            The prefix argument is not parsed for macro names or delimiters, but used verbatim as
            if it were escaped.

            Examples:
                       .Pf $ Ar variable_name
                       .Pf . Ar macro_name
                       .Pf 0x Ar hex_digits

            See also Ns and Sm.

       Po block
            Multi-line version of Pq.

       Pp
            Break a paragraph.  This will assert vertical space between prior and subsequent
            macros and/or text.

            Paragraph breaks are not needed before or after Sh or Ss macros or before displays
            (Bd line) or lists (Bl) unless the -compact flag is given.

       Pq line
            Parenthesised enclosure.

            See also Po.

       Qc
            Close quoted context opened by Qo.

       Ql line
            In-line literal display.  This can be used for complete command invocations and for
            multi-word code examples when an indented display is not desired.

            See also Dl and Bd -literal.

       Qo block
            Multi-line version of Qq.

       Qq line
            Encloses its arguments in "typewriter" double-quotes.  Consider using Dq.

            See also Dq, Sq, and Qo.

       Re
            Close an Rs block.  Does not have any tail arguments.

       Rs
            Begin a bibliographic (“reference”) block.  Does not have any head arguments.  The
            block macro may only contain %A, %B, %C, %D, %I, %J, %N, %O, %P, %Q, %R, %T, %U, and
            %V child macros (at least one must be specified).

            Examples:
                  .Rs
                  .%A J. E. Hopcroft
                  .%A J. D. Ullman
                  .%B Introduction to Automata Theory, Languages, and Computation
                  .%I Addison-Wesley
                  .%C Reading, Massachusetts
                  .%D 1979
                  .Re

            If an Rs block is used within a SEE ALSO section, a vertical space is asserted before
            the rendered output, else the block continues on the current line.

       Rv -std [function ...]
            Insert a standard sentence regarding a function call's return value of 0 on success
            and -1 on error, with the errno libc global variable set on error.

            If function is not specified, the document's name set by Nm is used.  Multiple
            function arguments are treated as separate functions.

            See also Ex.

       Sc
            Close single-quoted context opened by So.

       Sh TITLE LINE
            Begin a new section.  For a list of conventional manual sections, see MANUAL
            STRUCTURE.  These sections should be used unless it's absolutely necessary that
            custom sections be used.

            Section names should be unique so that they may be keyed by Sx.  Although this macro
            is parsed, it should not consist of child node or it may not be linked with Sx.

            See also Pp, Ss, and Sx.

       Sm [on | off]
            Switches the spacing mode for output generated from macros.

            By default, spacing is on.  When switched off, no white space is inserted between
            macro arguments and between the output generated from adjacent macros, but text lines
            still get normal spacing between words and sentences.

            When called without an argument, the Sm macro toggles the spacing mode.  Using this
            is not recommended because it makes the code harder to read.

       So block
            Multi-line version of Sq.

       Sq line
            Encloses its arguments in ‘typewriter’ single-quotes.

            See also Dq, Qq, and So.

       Ss Title line
            Begin a new subsection.  Unlike with Sh, there is no convention for the naming of
            subsections.  Except DESCRIPTION, the conventional sections described in MANUAL
            STRUCTURE rarely have subsections.

            Sub-section names should be unique so that they may be keyed by Sx.  Although this
            macro is parsed, it should not consist of child node or it may not be linked with Sx.

            See also Pp, Sh, and Sx.

       St -abbreviation
            Replace an abbreviation for a standard with the full form.  The following standards
            are recognised.  Where multiple lines are given without a blank line in between, they
            all refer to the same standard, and using the first form is recommended.

            C language standards

               -ansiC          ANSI X3.159-1989 (“ANSI C89”)
               -ansiC-89       ANSI X3.159-1989 (“ANSI C89”)
               -isoC           ISO/IEC 9899:1990 (“ISO C90”)
               -isoC-90        ISO/IEC 9899:1990 (“ISO C90”)
                               The original C standard.

               -isoC-amd1      ISO/IEC 9899/AMD1:1995 (“ISO C90, Amendment 1”)

               -isoC-tcor1     ISO/IEC 9899/TCOR1:1994 (“ISO C90, Technical Corrigendum 1”)

               -isoC-tcor2     ISO/IEC 9899/TCOR2:1995 (“ISO C90, Technical Corrigendum 2”)

               -isoC-99        ISO/IEC 9899:1999 (“ISO C99”)
                               The second major version of the C language standard.

               -isoC-2011      ISO/IEC 9899:2011 (“ISO C11”)
                               The third major version of the C language standard.
            POSIX.1 before the Single UNIX Specification

               -p1003.1-88     IEEE Std 1003.1-1988 (“POSIX.1”)
               -p1003.1        IEEE Std 1003.1 (“POSIX.1”)
                               The original POSIX standard, based on ANSI C.

               -p1003.1-90     IEEE Std 1003.1-1990 (“POSIX.1”)
               -iso9945-1-90   ISO/IEC 9945-1:1990 (“POSIX.1”)
                               The first update of POSIX.1.

               -p1003.1b-93    IEEE Std 1003.1b-1993 (“POSIX.1b”)
               -p1003.1b       IEEE Std 1003.1b (“POSIX.1b”)
                               Real-time extensions.

               -p1003.1c-95    IEEE Std 1003.1c-1995 (“POSIX.1c”)
                               POSIX thread interfaces.

               -p1003.1i-95    IEEE Std 1003.1i-1995 (“POSIX.1i”)
                               Technical Corrigendum.

               -p1003.1-96     ISO/IEC 9945-1:1996 (“POSIX.1”)
               -iso9945-1-96   ISO/IEC 9945-1:1996 (“POSIX.1”)
                               Includes POSIX.1-1990, 1b, 1c, and 1i.
            X/Open Portability Guide version 4 and related standards

               -xpg3           X/Open Portability Guide Issue 3 (“XPG3”)
                               An XPG4 precursor, published in 1989.

               -p1003.2        IEEE Std 1003.2 (“POSIX.2”)
               -p1003.2-92     IEEE Std 1003.2-1992 (“POSIX.2”)
               -iso9945-2-93   ISO/IEC 9945-2:1993 (“POSIX.2”)
                               An XCU4 precursor.

               -p1003.2a-92    IEEE Std 1003.2a-1992 (“POSIX.2”)
                               Updates to POSIX.2.

               -xpg4           X/Open Portability Guide Issue 4 (“XPG4”)
                               Based on POSIX.1 and POSIX.2, published in 1992.
            Single UNIX Specification version 1 and related standards

               -susv1          Version 1 of the Single UNIX Specification (“SUSv1”)
               -xpg4.2         X/Open Portability Guide Issue 4, Version 2 (“XPG4.2”)
                               This standard was published in 1994.  It was used as the basis for
                               UNIX 95 certification.  The following three refer to parts of it.

               -xsh4.2         X/Open System Interfaces and Headers Issue 4, Version 2 (“XSH4.2”)

               -xcurses4.2     X/Open Curses Issue 4, Version 2 (“XCURSES4.2”)

               -p1003.1g-2000
                               IEEE Std 1003.1g-2000 (“POSIX.1g”)
                               Networking APIs, including sockets.

               -svid4          System V Interface Definition, Fourth Edition (“SVID4”),
                               Published in 1995.
            Single UNIX Specification version 2 and related standards

               -susv2          Version 2 of the Single UNIX Specification (“SUSv2”) This Standard
                               was published in 1997 and is also called X/Open Portability Guide
                               version 5.  It was used as the basis for UNIX 98 certification.
                               The following refer to parts of it.

               -xbd5           X/Open Base Definitions Issue 5 (“XBD5”)

               -xsh5           X/Open System Interfaces and Headers Issue 5 (“XSH5”)

               -xcu5           X/Open Commands and Utilities Issue 5 (“XCU5”)

               -xns5           X/Open Networking Services Issue 5 (“XNS5”)
               -xns5.2         X/Open Networking Services Issue 5.2 (“XNS5.2”)
            Single UNIX Specification version 3

               -p1003.1-2001
                              IEEE Std 1003.1-2001 (“POSIX.1”)
               -susv3         Version 3 of the Single UNIX Specification (“SUSv3”)
                              This standard is based on C99, SUSv2, POSIX.1-1996, 1d, and 1j.  It
                              is also called X/Open Portability Guide version 6.  It is used as
                              the basis for UNIX 03 certification.

               -p1003.1-2004
                              IEEE Std 1003.1-2004 (“POSIX.1”)
                              The second and last Technical Corrigendum.
            Single UNIX Specification version 4

               -p1003.1-2008   IEEE Std 1003.1-2008 (“POSIX.1”)
               -susv4          Version 4 of the Single UNIX Specification (“SUSv4”)
                               This standard is also called X/Open Portability Guide version 7.
            Other standards

               -ieee754        IEEE Std 754-1985
                               Floating-point arithmetic.

               -iso8601        ISO 8601
                               Representation of dates and times, published in 1988.

               -iso8802-3      ISO 8802-3: 1989
                               Ethernet local area networks.

               -ieee1275-94    IEEE Std 1275-1994 (“Open Firmware”)
       Sx Title line
            Reference a section or subsection in the same manual page.  The referenced section or
            subsection name must be identical to the enclosed argument, including whitespace.

            Examples:
                  .Sx MANUAL STRUCTURE

            See also Sh and Ss.

       Sy word ...
            Request a boldface font.

            This is most often used to indicate importance or seriousness (not to be confused
            with stress emphasis, see Em).  When none of the semantic macros fit, it is also
            adequate for syntax elements that have to be given or that appear verbatim.

            Examples:
                  .Sy Warning :
                  If
                  .Sy s
                  appears in the owner permissions, set-user-ID mode is set.
                  This utility replaces the former
                  .Sy dumpdir
                  program.

            See also Em, No, and Ql.

       Ta
            Table cell separator in Bl -column lists; can only be used below It.

       Tg [term]
            Announce that the next input line starts a definition of the term.  This macro must
            appear alone on its own input line.  The argument defaults to the first argument of
            the first macro on the next line.  The argument may not contain whitespace
            characters, not even when it is quoted.  This macro is a mandoc(1) extension and is
            typically ignored by other formatters.

            When viewing terminal output with less(1), the interactive :t command can be used to
            go to the definition of the term as described for the MANPAGER variable in man(1);
            when producing HTML output, a fragment identifier (id attribute) is generated, to be
            used for deep linking to this place of the document.

            In most cases, adding a Tg macro would be redundant because mandoc(1) is able to
            automatically tag most definitions.  This macro is intended for cases where automatic
            tagging of a term is unsatisfactory, for example if a definition is not tagged
            automatically (false negative) or if places are tagged that do not define the term
            (false positives).  When there is at least one Tg macro for a term, no other places
            are automatically marked as definitions of that term.

       Tn word ...
            Supported only for compatibility, do not use this in new manuals.  Even though the
            macro name (“tradename”) suggests a semantic function, historic usage is
            inconsistent, mostly using it as a presentation-level macro to request a small caps
            font.

       Ud
            Supported only for compatibility, do not use this in new manuals.  Prints out
            “currently under development.”

       Ux
            Supported only for compatibility, do not use this in new manuals.  Prints out “UNIX”.

       Va [type] identifier ...
            A variable name.

            Examples:
                  .Va foo
                       .Va const char *bar
            ;

            For function arguments and parameters, use Fa instead.  For declarations of global
            variables in the SYNOPSIS section, use Vt.

       Vt type [identifier]
            A variable type.

            This is also used for indicating global variables in the SYNOPSIS section, in which
            case a variable name is also specified.  Note that it accepts Block partial-implicit
            syntax when invoked as the first macro on an input line in the SYNOPSIS section, else
            it accepts ordinary In-line syntax.  In the former case, this macro starts a new
            output line, and a blank line is inserted in front if there is a preceding function
            definition or include directive.

            Examples:
                  .Vt unsigned char
                       .Vt extern const char * const sys_signame[] ;

            For parameters in function prototypes, use Fa instead, for function return types Ft,
            and for variable names outside the SYNOPSIS section Va, even when including a type
            with the name.  See also MANUAL STRUCTURE.

       Xc
            Close a scope opened by Xo.

       Xo block
            Extend the header of an It macro or the body of a partial-implicit block macro beyond
            the end of the input line.  This macro originally existed to work around the
            9-argument limit of historic roff(7).

       Xr name section
            Link to another manual ("cross-reference").

            Cross reference the name and section number of another man page.

            Examples:
                  .Xr mandoc 1
                       .Xr mandoc 1 ;
                       .Xr mandoc 1 Ns s behaviour

MACRO SYNTAX

       The syntax of a macro depends on its classification.  In this section, ‘-arg’ refers to
       macro arguments, which may be followed by zero or more ‘parm’ parameters; ‘Yo’ opens the
       scope of a macro; and if specified, ‘Yc’ closes it out.

       The Callable column indicates that the macro may also be called by passing its name as an
       argument to another macro.  For example, ‘.Op Fl O Ar file’ produces ‘[-O file]’.  To
       prevent a macro call and render the macro name literally, escape it by prepending a zero-
       width space, ‘\&’.  For example, ‘Op \&Fl O’ produces ‘[Fl O]’.  If a macro is not
       callable but its name appears as an argument to another macro, it is interpreted as opaque
       text.  For example, ‘.Fl Sh’ produces ‘-Sh’.

       The Parsed column indicates whether the macro may call other macros by receiving their
       names as arguments.  If a macro is not parsed but the name of another macro appears as an
       argument, it is interpreted as opaque text.

       The Scope column, if applicable, describes closure rules.

   Block full-explicit
       Multi-line scope closed by an explicit closing macro.  All macros contains bodies; only Bf
       and (optionally) Bl contain a head.

             .Yo [-arg [parm...]] [head...]
             [body...]
             .Yc

                          Macro   Callable   Parsed   Scope

                          Bd      No         No       closed by Ed

                          Bf      No         No       closed by Ef

                          Bk      No         No       closed by Ek

                          Bl      No         No       closed by El

                          Ed      No         No       opened by Bd

                          Ef      No         No       opened by Bf

                          Ek      No         No       opened by Bk

                          El      No         No       opened by Bl

   Block full-implicit
       Multi-line scope closed by end-of-file or implicitly by another macro.  All macros have
       bodies; some (It -bullet, -hyphen, -dash, -enum, -item) don't have heads; only one (It in
       Bl -column) has multiple heads.

             .Yo [-arg [parm...]] [head... [Ta head...]]
             [body...]

                          Macro   Callable   Parsed   Scope

                          It      No         Yes      closed by It, El

                          Nd      No         No       closed by Sh

                          Nm      No         Yes      closed by Nm, Sh, Ss

                          Sh      No         Yes      closed by Sh

                          Ss      No         Yes      closed by Sh, Ss

       Note that the Nm macro is a Block full-implicit macro only when invoked as the first macro
       in a SYNOPSIS section line, else it is In-line.

   Block partial-explicit
       Like block full-explicit, but also with single-line scope.  Each has at least a body and,
       in limited circumstances, a head (Fo, Eo) and/or tail (Ec).

             .Yo [-arg [parm...]] [head...]
             [body...]
             .Yc [tail...]

             .Yo [-arg [parm...]] [head...] [body...] Yc [tail...]

                          Macro   Callable   Parsed   Scope

                          Ac      Yes        Yes      opened by Ao

                          Ao      Yes        Yes      closed by Ac

                          Bc      Yes        Yes      closed by Bo

                          Bo      Yes        Yes      opened by Bc

                          Brc     Yes        Yes      opened by Bro

                          Bro     Yes        Yes      closed by Brc

                          Dc      Yes        Yes      opened by Do

                          Do      Yes        Yes      closed by Dc

                          Ec      Yes        Yes      opened by Eo

                          Eo      Yes        Yes      closed by Ec

                          Fc      Yes        Yes      opened by Fo

                          Fo      No         No       closed by Fc

                          Oc      Yes        Yes      closed by Oo

                          Oo      Yes        Yes      opened by Oc

                          Pc      Yes        Yes      closed by Po

                          Po      Yes        Yes      opened by Pc

                          Qc      Yes        Yes      opened by Oo

                          Qo      Yes        Yes      closed by Oc

                          Re      No         No       opened by Rs

                          Rs      No         No       closed by Re

                          Sc      Yes        Yes      opened by So

                          So      Yes        Yes      closed by Sc

                          Xc      Yes        Yes      opened by Xo

                          Xo      Yes        Yes      closed by Xc

   Block partial-implicit
       Like block full-implicit, but with single-line scope closed by the end of the line.

             .Yo [-arg [val...]] [body...] [res...]

                          Macro   Callable   Parsed

                          Aq      Yes        Yes

                          Bq      Yes        Yes

                          Brq     Yes        Yes

                          D1      No         Yes

                          Dl      No         Yes

                          Dq      Yes        Yes

                          En      Yes        Yes

                          Op      Yes        Yes

                          Pq      Yes        Yes

                          Ql      Yes        Yes

                          Qq      Yes        Yes

                          Sq      Yes        Yes

                          Vt      Yes        Yes

       Note that the Vt macro is a Block partial-implicit only when invoked as the first macro in
       a SYNOPSIS section line, else it is In-line.

   Special block macro
       The Ta macro can only be used below It in Bl -column lists.  It delimits blocks
       representing table cells; these blocks have bodies, but no heads.

                          Macro   Callable   Parsed   Scope

                          Ta      Yes        Yes      closed by Ta, It

   In-line
       Closed by the end of the line, fixed argument lengths, and/or subsequent macros.  In-line
       macros have only text children.  If a number (or inequality) of arguments is (n), then the
       macro accepts an arbitrary number of arguments.

             .Yo [-arg [val...]] [args...] [res...]

             .Yo [-arg [val...]] [args...] Yc...

             .Yo [-arg [val...]] arg0 arg1 argN

                          Macro   Callable   Parsed   Arguments

                          %A      No         No       >0

                          %B      No         No       >0

                          %C      No         No       >0

                          %D      No         No       >0

                          %I      No         No       >0

                          %J      No         No       >0

                          %N      No         No       >0

                          %O      No         No       >0

                          %P      No         No       >0

                          %Q      No         No       >0

                          %R      No         No       >0

                          %T      No         No       >0

                          %U      No         No       >0

                          %V      No         No       >0

                          Ad      Yes        Yes      >0

                          An      Yes        Yes      >0

                          Ap      Yes        Yes      0

                          Ar      Yes        Yes      n

                          At      Yes        Yes      1

                          Bsx     Yes        Yes      n

                          Bt      No         No       0

                          Bx      Yes        Yes      n

                          Cd      Yes        Yes      >0

                          Cm      Yes        Yes      >0

                          Db      No         No       1

                          Dd      No         No       n

                          Dt      No         No       n

                          Dv      Yes        Yes      >0

                          Dx      Yes        Yes      n

                          Em      Yes        Yes      >0

                          Er      Yes        Yes      >0

                          Es      Yes        Yes      2

                          Ev      Yes        Yes      >0

                          Ex      No         No       n

                          Fa      Yes        Yes      >0

                          Fd      No         No       >0

                          Fl      Yes        Yes      n

                          Fn      Yes        Yes      >0

                          Fr      Yes        Yes      >0

                          Ft      Yes        Yes      >0

                          Fx      Yes        Yes      n

                          Hf      No         No       n

                          Ic      Yes        Yes      >0

                          In      No         No       1

                          Lb      No         No       1

                          Li      Yes        Yes      >0

                          Lk      Yes        Yes      >0

                          Lp      No         No       0

                          Ms      Yes        Yes      >0

                          Mt      Yes        Yes      >0

                          Nm      Yes        Yes      n

                          No      Yes        Yes      >0

                          Ns      Yes        Yes      0

                          Nx      Yes        Yes      n

                          Os      No         No       n

                          Ot      Yes        Yes      >0

                          Ox      Yes        Yes      n

                          Pa      Yes        Yes      n

                          Pf      Yes        Yes      1

                          Pp      No         No       0

                          Rv      No         No       n

                          Sm      No         No       <2

                          St      No         Yes      1

                          Sx      Yes        Yes      >0

                          Sy      Yes        Yes      >0

                          Tg      No         No       <2

                          Tn      Yes        Yes      >0

                          Ud      No         No       0

                          Ux      Yes        Yes      n

                          Va      Yes        Yes      n

                          Vt      Yes        Yes      >0

                          Xr      Yes        Yes      2

   Delimiters
       When a macro argument consists of one single input character considered as a delimiter,
       the argument gets special handling.  This does not apply when delimiters appear in
       arguments containing more than one character.  Consequently, to prevent special handling
       and just handle it like any other argument, a delimiter can be escaped by prepending a
       zero-width space (‘\&’).  In text lines, delimiters never need escaping, but may be used
       as normal punctuation.

       For many macros, when the leading arguments are opening delimiters, these delimiters are
       put before the macro scope, and when the trailing arguments are closing delimiters, these
       delimiters are put after the macro scope.  Spacing is suppressed after opening delimiters
       and before closing delimiters.  For example,

       renders as:

             ([⟨word⟩
       ]).

       Opening delimiters are:

             (       left parenthesis
             [       left bracket

       Closing delimiters are:

             .       period
             ,       comma
             :       colon
             ;       semicolon
             )       right parenthesis
             ]       right bracket
             ?       question mark
             !       exclamation mark

       Note that even a period preceded by a backslash (‘\.’) gets this special handling; use
       ‘\&.’ to prevent that.

       Many in-line macros interrupt their scope when they encounter delimiters, and resume their
       scope when more arguments follow that are not delimiters.  For example,

       renders as:

             -a (-b | -c | -d) -e

       This applies to both opening and closing delimiters, and also to the middle delimiter,
       which does not suppress spacing:

             |       vertical bar

       As a special case, the predefined string \*(Ba is handled and rendered in the same way as
       a plain ‘|’ character.  Using this predefined string is not recommended in new manuals.

       Appending a zero-width space (‘\&’) to the end of an input line is also useful to prevent
       the interpretation of a trailing period, exclamation or question mark as the end of a
       sentence, for example when an abbreviation happens to occur at the end of a text or macro
       input line.

   Font handling
       In mdoc documents, usage of semantic markup is recommended in order to have proper fonts
       automatically selected; only when no fitting semantic markup is available, consider
       falling back to Physical markup macros.  Whenever any mdoc macro switches the roff(7) font
       mode, it will automatically restore the previous font when exiting its scope.  Manually
       switching the font using the roff(7) ‘\f’ font escape sequences is never required.

COMPATIBILITY

       This section provides an incomplete list of compatibility issues between mandoc and GNU
       troff ("groff").

       The following problematic behaviour is found in groff:

       -   Pa does not format its arguments when used in the FILES section under certain list
           types.
       -   Ta can only be called by other macros, but not at the beginning of a line.
       -   ‘\f’ (font face) and ‘\F’ (font family face) Text Decoration escapes behave
           irregularly when specified within line-macro scopes.
       -   Negative scaling units return to prior lines.  Instead, mandoc truncates them to zero.

       The following features are unimplemented in mandoc:

       -   Bd -file file is unsupported for security reasons.
       -   Bd -filled does not adjust the right margin, but is an alias for Bd -ragged.
       -   Bd -literal does not use a literal font, but is an alias for Bd -unfilled.
       -   Bd -offset center and -offset right don't work.  Groff does not implement centered and
           flush-right rendering either, but produces large indentations.

SEE ALSO

       man(1), mandoc(1), eqn(7), man(7), mandoc_char(7), roff(7), tbl(7)

       The web page extended documentation for the mdoc language: https://mandoc.bsd.lv/mdoc/
       provides a few tutorial-style pages for beginners, an extensive style guide for advanced
       authors, and an alphabetic index helping to choose the best macros for various kinds of
       content.

       The manual page groff_mdoc(7): https://man.voidlinux.org/groff_mdoc contained in the
       “groff” package documents exactly the same language in a somewhat different style.

HISTORY

       The mdoc language first appeared as a troff macro package in 4.4BSD.  It was later
       significantly updated by Werner Lemberg and Ruslan Ermilov in groff-1.17.  The standalone
       implementation that is part of the mandoc(1) utility written by Kristaps Dzonsons appeared
       in OpenBSD 4.6.

AUTHORS

       The mdoc reference was written by Kristaps Dzonsons <kristaps@bsd.lv>.