MDOC(7)

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 mdoc followed by -.

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, & 9 only.
    .\" Not used in OpenBSD.
    .Sh SYNOPSIS
    .Nm progname
    .Op Fl options
    .Ar
    .Sh DESCRIPTION
    The
    .Nm
    utility processes files ...
    .\" .Sh IMPLEMENTATION NOTES
    .\" Not used in OpenBSD.
    .\" .Sh RETURN VALUES
    .\" For sections 2, 3, & 9 only.
    .\" .Sh ENVIRONMENT
    .\" For sections 1, 6, 7, & 8 only.
    .\" .Sh FILES
    .\" .Sh EXIT STATUS
    .\" For sections 1, 6, & 8 only.
    .\" .Sh EXAMPLES
    .\" .Sh DIAGNOSTICS
    .\" For sections 1, 4, 6, 7, & 8 only.
    .\" .Sh ERRORS
    .\" For sections 2, 3, & 9 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 ‘mdoc’ names should be separated by commas.

The mdoc macro(s) must precede the - macro.

See mdoc and -.

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.

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,,, and ( 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 mdoc,, Fd,, (,,, and. All of these macros are output on their own line. If two such dissimilar macros are pairwise invoked (except for before ( or), they are separated by a vertical space, unless in the case of (,, and, which are always separated by vertical space.

When text and macros following an mdoc 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 mdoc macro, up to the next mdoc, 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 arguments are as follows:
    .Bl -tag -width Ds
    .It Fl v
    Print verbose information.
    .El

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.

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.

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 ~.

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 conditions. This is most useful in section 4 manuals. 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 error handling in sections 2, 3, and 9.

See.

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.

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.

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

See.

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.

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 [volume | arch]
Os | operating system version: [system [version]]
mdoc | document name (one argument)
- | document description (one line)

  Sections and cross references
Sh | section header (one line)
Ss | subsection header (one line)
 | internal cross reference to a section or subsection
 | cross reference to another manual page: name section
Pp, Lp | 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)
Bl, El | list block:
- type [-width val] [-offset val] [-compact]
It | list item (syntax depends on - type)
 | | table cell separator in Bl -column lists
Rs, %*, Re | bibliographic block (references)

  Spacing control
 | prefix, no following horizontal space (one argument)
 | roman font, no preceding horizontal space (no arguments)
'| apostrophe without surrounding whitespace (no arguments)
Sm | switch horizontal spacing mode: on | off
Bk, Ek | keep block: -words
br | force output line break in text mode (no arguments)
sp | force vertical space: [height]

  Semantic markup for command line utilities:
mdoc | start a SYNOPSIS block with the name of a utility
- | command line options (flags) (>=0 arguments)
 | command modifier (>0 arguments)
file ... | command arguments (>=0 arguments)
[, [,] | optional syntax elements (enclosure)]
 | internal or interactive command (>0 arguments)
 | environmental variable (>0 arguments)
~ | file system path (>=0 arguments)

  Semantic markup for function libraries:
 | function library (one argument)
 | include file (one argument)
 | function type (>0 arguments)
,() | function block: funcname
 | function name:
[functype] funcname [ [argtype] argname]
 | function argument (>0 arguments)
 | variable type (>0 arguments)
 | variable name (>0 arguments)
 | defined variable or preprocessor constant (>0 arguments)
 | error constant (>0 arguments)
 | environmental variable (>0 arguments)

  Various semantic markup:
 | author name (>0 arguments)
 | hyperlink: uri [name]
~ | “mailto” hyperlink: address
 | kernel configuration declaration (>0 arguments)
 | memory address (>0 arguments)
 | mathematical symbol (>0 arguments)
 | tradename (>0 arguments)

  Physical markup
 | italic font or underline (emphasis) (>0 arguments)
 | boldface font (symbolic) (>0 arguments)
 | typewriter font (literal) (>0 arguments)
 | return to roman font (normal) (no arguments)
Bf, Ef | font block:
[- type | | |]

  Physical enclosures
“, “,” | enclose in typographic double quotes: “text””
", "," | enclose in typewriter double quotes: "text""
‘, ‘,’ | enclose in single quotes: ‘text’’
‘| single-quoted literal text: ‘text’’
(, (,) | enclose in parentheses: (text))
[, [,] | enclose in square brackets: [text]]
{, {,} | enclose in curly braces: {text}}
<, <,> | enclose in angle brackets: <text>>
, | generic enclosure

  Text production
Ex -std | standard command exit values: [utility ...]
Rv -std | standard function return values: [function ...]
 | reference to a standards document (one argument)
UNIX | UNIX
AT&T UNIX | AT&T UNIX
BSD | BSD
BSD/OS | BSD/OS
NetBSD | NetBSD
FreeBSD | FreeBSD
OpenBSD | OpenBSD
DragonFly | DragonFly

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

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

  %C
Publication city or location of an Rs block.

  %D
Publication date of an Rs block. Recommended formats of arguments are month day, year or just year.

  %I
Publisher or issuer name of an Rs block.

  %J
Journal name of an Rs block.

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

  %O
Optional information of an Rs block.

  %P
Book or journal page number of an Rs block.

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

  %R
Technical report name of an Rs block.

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

  %U
URI of reference document.

  %V
Volume number of an Rs block.

Close an < block. Does not have any tail arguments.

Memory address. Do not use this for postal addresses.

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

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.
-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 <kristaps@bsd.lv>

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

Examples:
    .Fl -key=<val>

See also <>.

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'd

Encloses its arguments in angle brackets.

Examples:
    .Fl -key=<val>

Remarks: this macro is often abused for rendering URIs, which should instead use or ~, or to note pre-processor “#include” statements, which should use.

See also <.

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 file ... macro are names and placeholders for command arguments; for fixed strings to be passed verbatim as arguments, use - or.

Formats an AT&T version. Accepts one optional argument:

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

Note that these arguments do not begin with a hyphen.

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

See also BSD/OS, BSD, DragonFly, FreeBSD, NetBSD, OpenBSD, and UNIX.

Close a [ block. Does not have any tail arguments.

  Bd
Begin a display block. Its syntax is as follows:

.Bd -type [-offset width] [-compact]

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 centre-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 centre 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
Change the font mode for a scoped block of text. Its syntax is as follows:

.Bf [ -emphasis | -literal | -symbolic | | |]

The -emphasis and argument are equivalent, as are -symbolic and, and -literal and. 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, Ef,, and.

  Bk
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 syntax is as follows:

    .Bk -words

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

The following example will not break within each [] 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
Begin a list. Lists consist of items specified using the It macro, containing a head or a body or both. The list syntax is as follows:

.Bl -type [-width val] [-offset val] [-compact] [HEAD ...]

The list type is mandatory and must be specified first. The -width and -offset arguments accept 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, each argument specifies the width of one column, using either the scaling width syntax described in roff(7) or the string length of the argument. 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.

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

Examples:
    .Bo 1 ,
    .Dv BUFSIZ Bc

See also [].

Encloses its arguments in square brackets.

Examples:
    .Bq 1, BUFSIZ

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

See also [.

Close a { block. Does not have any tail arguments.

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

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

See also {}.

Encloses its arguments in curly braces.

Examples:
    .Brq 1, ..., n

See also {.

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&T UNIX, BSD, DragonFly, FreeBSD, NetBSD, OpenBSD, and UNIX.

  Bt
Prints “is currently in beta test.”

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&T UNIX, BSD/OS, DragonFly, FreeBSD, NetBSD, OpenBSD, and UNIX.

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 declarations. This practise is discouraged.

Command modifiers. Typically used for fixed strings passed as arguments, unless - is more appropriate. Also useful when specifying configuration options or keys.

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
    .Cm IdentityFile Pa ~/.ssh/id_rsa
    .Cm LogLevel Dv DEBUG

  D1
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 -abcdefgh

See also Bd and Dl.

  Db
Switch debugging mode. Its syntax is as follows:

    .Db on | off

This macro is ignored by mandoc(1).

Close a “ block. Does not have any tail arguments.

  Dd
Document date. This is the mandatory first macro of any mdoc manual. Its syntax is as follows:

    .Dd month day, year

The month is the full English month name, the day is an optionally zero-padded numeral, 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.
-   A few alternative date formats are accepted as well and converted to the standard form.
-   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 $Mdocdate: July 21 2007$
    .Dd July 21, 2007

See also Dt and Os.

  Dl
One-line intended 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 Bd and D1.

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 “”.

Encloses its arguments in “typographic” double-quotes.

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

See also "", ‘’, and “.

  Dt
Document title. This is the mandatory second macro of any mdoc file. Its syntax is as follows:

.Dt [ title [ section [volume] [arch]]]

Its arguments are as follows:

title
    The document's title (name), defaulting to “UNKNOWN” if unspecified. It should be capitalised.

section
    The manual section. This may be one of 1 (utilities), 2 (system calls), 3 (libraries), 3p (Perl libraries), 4 (devices), 5 (file formats), 6 (games), 7 (miscellaneous), 8 (system utilities), 9 (kernel functions), X11 (X Window System), X11R6 (X Window System), unass (unassociated), local (local system), draft (draft manual), or paper (paper). It should correspond to the manual's filename suffix and defaults to “1” if unspecified.

volume
    This overrides the volume inferred from section. This field is optional, and if specified, must be one of USD (users' supplementary documents), PS1 (programmers' supplementary documents), AMD (administrators' supplementary documents), SMM (system managers' manuals), URM (users' reference manuals), PRM (programmers' reference manuals), KM (kernel manuals), IND (master index), MMI (master index), LOCAL (local manuals), LOC (local manuals), or CON (contributed manuals).

arch
    This specifies the machine architecture a manual page applies to, where relevant. For OpenBSD, the following are valid architectures: alpha, amd64, armish, aviion, beagle, hp300, hppa, hppa64, i386, ia64, landisk, loongson, luna88k, macppc, mips64, mvme68k, mvme88k, octeon, sgi, socppc, solbourne, sparc, sparc64, vax, and zaurus.

Examples:
    .Dt FOO 1
    .Dt FOO 4 KM
    .Dt FOO 9 i386

See also Dd and Os.

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

Examples:
    .Dv NULL
    .Dv BUFSIZ
    .Dv STDOUT_FILENO

See also and for special-purpose constants and for variable symbols.

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

Examples:
    .Dx 2.4.1
    .Dx

See also AT&T UNIX, BSD/OS, BSD, FreeBSD, NetBSD, OpenBSD, and UNIX.

Close a scope started by. Its syntax is as follows:

    . [TERM]

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

  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 Bl and It.

Denotes text that should be emphasised. Note that this is a presentation term and should not be used for stylistically decorating technical terms. Depending on the output device, this is usually represented using an italic font or underlined characters.

Examples:
    .Em Warnings!
    .Em Remarks:

See also Bf,,, and.

  En
This macro is obsolete and not implemented in mandoc(1).

An arbitrary enclosure. Its syntax is as follows:

    .[TERM]

The TERM argument is used as the enclosure head, for example, specifying \(lq will emulate “.

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 for general constants.

  Es
This macro is obsolete and not implemented.

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

Examples:
    .Ev DISPLAY
    .Ev PATH

See also for general constants.

  Ex
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. Its syntax is as follows:

    .Ex -std [utility ...]

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

See also Rv.

Function argument. Its syntax is as follows:

. [argtype] argname

This may be invoked for names with or without the corresponding type. It is also used to specify the field name of a structure. Most often, the macro is used in the SYNOPSIS within ( section 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, the last argument will also have a trailing comma.

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

See also (.

End a function context started by (.

  Fd
Historically used to document include files. This usage has been deprecated in favour of. Do not use this macro.

See also MANUAL STRUCTURE and.

Command-line flag or option. Used when listing arguments to command-line utilities. Prints a fixed-width hyphen ‘-’ directly followed by each argument. If no arguments are provided, a hyphen is printed followed by a space. If the argument is a macro, a hyphen is prefixed to the subsequent macro output.

Examples:
    .Fl R Op Fl H | L | P
    .Op Fl 1AaCcdFfgHhikLlmnopqRrSsTtux
    .Fl type Cm d Fl name Pa CVS
    .Fl Ar signal_number
    .Fl o Fl

See also.

A function name. Its syntax is as follows:

. [functype] funcname [[argtype] argname]

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 instead. See also MANUAL STRUCTURE, (, and.

Begin a function block. This is a multi-line version of. Its syntax is as follows:

    .(funcname

Invocations usually occur in the following context:

.functype
.(funcname
.[argtype] argname
...
.)

A ( scope is closed by).

See also MANUAL STRUCTURE,,), and.

This macro is obsolete and not implemented in mandoc(1).

It was used to show function return values. The syntax was:

    .value

A function type. Its syntax is as follows:

    .functype

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

Examples:
    .Ft int
    .Ft functype
    .Fn funcname

See also MANUAL STRUCTURE,, and (.

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&T UNIX, BSD/OS, BSD, DragonFly, NetBSD, OpenBSD, and UNIX.

  Hf
This macro is not implemented in mandoc(1).

It was used to include the contents of a (header) file literally. The syntax was:

    .Hf filename

Designate an internal or interactive command. This is similar to but used for instructions rather than values.

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

Note that using Bd -literal or D1 is preferred for displaying code; the macro is used when referring to specific instructions.

An “include” file. 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. This is most often used in section 2, 3, and 9 manual pages.

Examples:
    .In sys/types.h

See also MANUAL STRUCTURE.

  It
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:

    .It args

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

    .It

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:

    .It [args]

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:

    .It cell [<TAB> cell ...]
    .It cell [| cell ...]

The arguments consist of one or more lines of text and macros representing a complete table line. Cells within the line are delimited by tabs or by the special | block macro. The tab cell delimiter may only be used within the It line itself; on following lines, only the | macro can be used to delimit cells, and | is only recognised as a macro when called by other macros, not 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 semicolon whitespace except for the last.

See also Bl.

Specify a library. The syntax is as follows:

    .library

The library parameter may be a system library, such as libz or libpam, 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 mdoc

Denotes text that should be in a literal font mode. Note that this is a presentation term and should not be used for stylistically decorating technical terms.

On terminal output devices, this is often indistinguishable from normal text.

See also Bf,,, and.

Format a hyperlink. Its syntax is as follows:

    .uri [name]

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

See also ~.

  Lp
Synonym for Pp.

Display a mathematical symbol. Its syntax is as follows:

    .symbol

Examples:
    .Ms sigma
    .Ms aleph

Format a “mailto:” hyperlink. Its syntax is as follows:

    .~ address

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

A one line description of the manual's content. This may only be invoked in the SYNOPSIS section subsequent the mdoc macro.

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

The - 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 mdoc.

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 mdoc 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 mdoc 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 macro rather than mdoc to mark up the name of the manual page.

Normal text. Closes the scope of any preceding in-line macro. When used after physical formatting macros like or, 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,, and.

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 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 and Sm.

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&T UNIX, BSD/OS, BSD, DragonFly, FreeBSD, OpenBSD, and UNIX.

Close multi-line [ context.

Multi-line version of [].

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

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 -a b
    .Op a | b

See also [.

  Os
Document operating system version. This is the mandatory third macro of any mdoc file. Its syntax is as follows:

    .Os [system [version]]

The optional system parameter specifies the relevant operating system or environment. Left unspecified, it defaults to the local operating system version. This is the suggested form.

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

See also Dd and Dt.

This macro is obsolete and not implemented in mandoc(1).

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

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&T UNIX, BSD/OS, BSD, DragonFly, FreeBSD, NetBSD, and UNIX.

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.

Close parenthesised context opened by (.

Removes the space between its argument (“prefix”) and the following macro. Its syntax is as follows:

    .Pf prefix macro arguments ...

This is equivalent to:

    .No prefixmacro arguments ...

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

See also and Sm.

Multi-line version of ().

  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) or lists (Bl) unless the -compact flag is given.

Parenthesised enclosure.

See also (.

Close quoted context opened by ".

Format a single-quoted literal. See also "" and ‘’.

Multi-line version of "".

Encloses its arguments in "typewriter" double-quotes. Consider using “”.

See also “”, ‘’, and ".

  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, Massachusettes
    .%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
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. Its syntax is as follows:

    .Rv -std [function ...]

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

See also Ex.

Close single-quoted context opened by ‘.

  Sh
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. Although this macro is parsed, it should not consist of child node or it may not be linked with.

See also Pp, Ss, and.

  Sm
Switches the spacing mode for output generated from macros. Its syntax is as follows:

    .Sm on | off

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.

Multi-line version of ‘’.

Encloses its arguments in ‘typewriter’ single-quotes.

See also “”, "", and ‘.

  Ss
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. Although this macro is parsed, it should not consist of child node or it may not be linked with.

See also Pp, Sh, and.

Replace an abbreviation for a standard with the full form. The following standards are recognised:

-p1003.1-88
    p1003.1-88
-p1003.1-90
    p1003.1-90
-p1003.1-96
    p1003.1-96
-p1003.1-2001
    p1003.1-2001
-p1003.1-2004
    p1003.1-2004
-p1003.1-2008
    p1003.1-2008
-p1003.1
    p1003.1
-p1003.1b
    p1003.1b
-p1003.1b-93
    p1003.1b-93
-p1003.1c-95
    p1003.1c-95
-p1003.1d-99
    p1003.1d-99
-p1003.1g-2000
    p1003.1g-2000
-p1003.1i-95
    p1003.1i-95
-p1003.1j-2000
    p1003.1j-2000
-p1003.1q-2000
    p1003.1q-2000
-p1003.2
    p1003.2
-p1003.2-92
    p1003.2-92
-p1003.2a-92
    p1003.2a-92
-p1387.2
    p1387.2
-p1387.2-95
    p1387.2-95
-isoC
    isoC
-isoC-90
    isoC-90
-isoC-amd1
    isoC-amd1
-isoC-tcor1
    isoC-tcor1
-isoC-tcor2
    isoC-tcor2
-isoC-99
    isoC-99
-isoC-2011
    isoC-2011
-iso9945-1-90
    iso9945-1-90
-iso9945-1-96
    iso9945-1-96
-iso9945-2-93
    iso9945-2-93
-ansiC
    ansiC
-ansiC-89
    ansiC-89
-ansiC-99
    ansiC-99
-ieee754
    ieee754
-iso8802-3
    iso8802-3
-iso8601
    iso8601
-ieee1275-94
    ieee1275-94
-xpg3
    xpg3
-xpg4
    xpg4
-xpg4.2
    xpg4.2
-xpg4.3
    xpg4.3
-xbd5
    xbd5
-xcu5
    xcu5
-xsh5
    xsh5
-xns5
    xns5
-xns5.2
    xns5.2
-xns5.2d2.0
    xns5.2d2.0
-xcurses4.2
    xcurses4.2
-susv2
    susv2
-susv3
    susv3
-svid4
    svid4

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.

Format enclosed arguments in symbolic (“boldface”). Note that this is a presentation term and should not be used for stylistically decorating technical terms.

See also Bf,,, and.

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

Format a tradename.

Since this macro is often implemented to use a small caps font, it has historically been used for acronyms (like ASCII) as well. Such usage is not recommended because it would use the same macro sometimes for semantical annotation, sometimes for physical formatting.

Examples:
    .Tn IBM

  Ud
Prints out “currently under development.”

Format the UNIX name. Accepts no argument.

Examples:
    .Ux

See also AT&T UNIX, BSD/OS, BSD, DragonFly, FreeBSD, NetBSD, and OpenBSD.

A variable name.

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

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.

Note that this should not be confused with, which is used for function return types.

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

See also MANUAL STRUCTURE and.

Close a scope opened by.

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).

Link to another manual ("cross-reference"). Its syntax is as follows:

    .name [section]

Cross reference the name and section number of another man page; omitting the section number is rarely useful.

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

  br
Emits a line-break. This macro should not be used; it is implemented for compatibility with historical manuals.

Consider using Pp in the event of natural paragraph breaks.

  sp
Emits vertical space. This macro should not be used; it is implemented for compatibility with historical manuals. Its syntax is as follows:

    .sp [height]

The height argument is a scaling width as described in roff(7). If unspecified, sp asserts a single vertical space.

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 -O 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, ‘[\&Fl O]’ produces ‘[-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 | | | closed by Ed
Bf | | | closed by Ef
Bk | | | closed by Ek
Bl | | | closed by El
Ed | | | opened by Bd
Ef | | | opened by Bf
Ek | | | opened by Bk
El | | | 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 | | Yes | closed by It, El
- | | | closed by Sh
mdoc | | Yes | closed by, Sh, Ss
Sh | | Yes | closed by Sh
Ss | | Yes | closed by Sh, Ss

Note that the mdoc 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 ( (,) and/or tail ().

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

Macro | Callable | Parsed | Scope
> | Yes | Yes | opened by <
<| Yes | Yes | closed by>
] | Yes | Yes | closed by [
[| Yes | Yes | opened by]
} | Yes | Yes | opened by {
{| Yes | Yes | closed by}
” | Yes | Yes | opened by “
“| Yes | Yes | closed by”
 | Yes | Yes | opened by
 | Yes | Yes | closed by
) | Yes | Yes | opened by (
(| | | closed by)
] | Yes | Yes | closed by [
[| Yes | Yes | opened by]
) | Yes | Yes | closed by (
(| Yes | Yes | opened by)
" | Yes | Yes | opened by [
"| Yes | Yes | closed by]
Re | | | opened by Rs
Rs | | | closed by Re
’ | Yes | Yes | opened by ‘
‘| Yes | Yes | closed by’
 | Yes | Yes | opened by
 | Yes | Yes | closed by

  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
<| Yes | Yes>
[| Yes | Yes]
{| Yes | Yes}
D1 | | Yes
Dl | | Yes
“| Yes | Yes”
[| Yes | Yes]
(| Yes | Yes)
‘| Yes | Yes’
"| Yes | Yes"
‘| Yes | Yes’
 | Yes | Yes

Note that the 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 | 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
 | | Yes | Yes | closed by |, 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 | | | >0
%B | | | >0
%C | | | >0
%D | | | >0
%I | | | >0
%J | | | >0
%N | | | >0
%O | | | >0
%P | | | >0
%Q | | | >0
%R | | | >0
%T | | | >0
%U | | | >0
%V | | | >0
 | Yes | Yes | >0
 | Yes | Yes | >0
'| Yes | Yes | 0
file ... | Yes | Yes | n
AT&T UNIX | Yes | Yes | 1
BSD/OS | Yes | Yes | n
Bt | | | 0
BSD | Yes | Yes | n
 | Yes | Yes | >0
 | Yes | Yes | >0
Db | | | 1
Dd | | | n
Dt | | | n
 | Yes | Yes | >0
DragonFly | Yes | Yes | n
 | Yes | Yes | >0
En | | | 0
 | Yes | Yes | >0
Es | | | 0
 | Yes | Yes | >0
Ex | | | n
 | Yes | Yes | >0
Fd | | | >0
- | Yes | Yes | n
 | Yes | Yes | >0
 | | | n
 | Yes | Yes | >0
FreeBSD | Yes | Yes | n
Hf | | | n
 | Yes | Yes | >0
 | | | 1
 | | | 1
 | Yes | Yes | >0
 | Yes | Yes | >0
Lp | | | 0
 | Yes | Yes | >0
~ | Yes | Yes | >0
mdoc | Yes | Yes | n
 | Yes | Yes | 0
 | Yes | Yes | 0
NetBSD | Yes | Yes | n
Os | | | n
 | | | n
OpenBSD | Yes | Yes | n
~ | Yes | Yes | n
 | Yes | Yes | 1
Pp | | | 0
Rv | | | n
Sm | | | 1
 | | Yes | 1
 | Yes | Yes | >0
 | Yes | Yes | >0
 | Yes | Yes | >0
Ud | | | 0
UNIX | Yes | Yes | n
 | Yes | Yes | n
 | Yes | Yes | >0
 | Yes | Yes | >0
br | | | 0
sp | | | 1

  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. For example,

    .<( [ word ] ) .>

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,

    .-a ( b | c \*(Ba d ) e

renders as:

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

This applies to both opening and closing delimiters, and also to the middle delimiter:

|   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.

  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 documents compatibility between mandoc and other troff implementations, at this time limited to GNU troff ("groff"). The term "historic groff" refers to groff versions before 1.17, which featured a significant update of the doc.tmac file.

Heirloom troff, the other significant troff implementation accepting -mdoc, is similar to historic groff.

The following problematic behaviour is found in groff:

-   Display macros ( Bd, Dl, and D1) may not be nested. (Historic groff only.)
-   AT&T UNIX with unknown arguments produces no output at all. (Historic groff only.) Newer groff and mandoc print "AT&T UNIX" and the arguments.
-   Bl -column does not recognise trailing punctuation characters when they immediately precede tabulator characters, but treats them as normal text and outputs a space before them.
-   Bd -ragged -compact does not start a new line. (Historic groff only.)
-   Dd with non-standard arguments behaves very strangely. When there are three arguments, they are printed verbatim. Any other number of arguments is replaced by the current date, but without any arguments the string “Epoch” is printed.
-   - does not print a dash for an empty argument. (Historic groff only.)
-   does not start a new line unless invoked as the line macro in the SYNOPSIS section. (Historic groff only.)
-   ( with non- children causes inconsistent spacing between arguments. In mandoc, a single space is always inserted between arguments.
-   in the SYNOPSIS causes inconsistent vertical spacing, depending on whether a prior has been invoked. See and for the normalised behaviour in mandoc.
-   ignores additional arguments and is not treated specially in the SYNOPSIS. (Historic groff only.)
-   It sometimes requires a -nested flag. (Historic groff only.) In new groff and mandoc, any list may be nested by default and -enum lists will restart the sequence only for the sub-list.
-   followed by a delimiter is incorrectly used in some manuals instead of properly quoting that character, which sometimes works with historic groff.
-   only accepts a single link-name argument; the remainder is misformatted.
-   ~ does not format its arguments when used in the FILES section under certain list types.
-   | can only be called by other macros, but not at the beginning of a line.
-   %C is not implemented.
-   Historic groff only allows up to eight or nine arguments per macro input line, depending on the exact situation. Providing more arguments causes garbled output. The number of arguments on one input line is not limited with mandoc.
-   Historic groff has many un-callable macros. Most of these (excluding some block-level macros) are callable in new groff and mandoc.
-   ‘|’ (vertical bar) is not fully supported as a delimiter. (Historic groff only.)
-   ‘\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.
-   Bd -offset center and -offset right. Groff does not implement centred and flush-right rendering either, but produces large indentations.
-   The ‘\h’ (horizontal position), ‘\v’ (vertical position), ‘\m’ (text colour), ‘\M’ (text filling colour), ‘\z’ (zero-length character), ‘\w’ (string length), ‘\k’ (horizontal position marker), ‘\o’ (text overstrike), and ‘\s’ (text size) escape sequences are all discarded in mandoc.
-   The ‘\f’ scaling unit is accepted by mandoc, but rendered as the default unit.
-   In quoted literals, groff allows pairwise double-quotes to produce a standalone double-quote in formatted output. This is not supported by mandoc.

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

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>.