Note that `Dd' can be empty. This found following a thread on discuss@

[mandoc.git] / mdoc.7

.\"     $Id: mdoc.7,v 1.142 2010/07/26 13:45:49 kristaps Exp $
.\"
.\" Copyright (c) 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
.\" Copyright (c) 2010 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: July 26 2010 $
.Dt MDOC 7
.Os
.Sh NAME
.Nm mdoc
.Nd mdoc language reference
.Sh DESCRIPTION
The
.Nm mdoc
language is used to format
.Bx
.Ux
manuals.
In this reference document, we describe its syntax, structure, and
usage.
Our reference implementation is mandoc; the
.Sx COMPATIBILITY
section describes compatibility with other troff \-mdoc implementations.
.Pp
An
.Nm
document follows simple rules: lines beginning with the control
character
.Sq \.
are parsed for macros.
Other lines are interpreted within the scope of
prior macros:
.Bd -literal -offset indent
\&.Sh Macro lines change control state.
Other lines are interpreted within the current state.
.Ed
.Sh LANGUAGE SYNTAX
.Nm
documents may contain only graphable 7-bit ASCII characters, the space
character, and, in certain circumstances, the tab character.
All manuals must have
.Ux
line terminators.
.Ss Comments
Text following a
.Sq \e\*q ,
whether in a macro or free-form text line, is ignored to the end of
line.
A macro line with only a control character and comment escape,
.Sq \&.\e\*q ,
is also ignored.
Macro lines with only a control character and optionally whitespace are
stripped from input.
.Ss Reserved Characters
Within a macro line, the following characters are reserved:
.Pp
.Bl -tag -width Ds -offset indent -compact
.It \&.
.Pq period
.It \&,
.Pq comma
.It \&:
.Pq colon
.It \&;
.Pq semicolon
.It \&(
.Pq left-parenthesis
.It \&)
.Pq right-parenthesis
.It \&[
.Pq left-bracket
.It \&]
.Pq right-bracket
.It \&?
.Pq question
.It \&!
.Pq exclamation
.It \&|
.Pq vertical bar
.El
.Pp
Use of reserved characters is described in
.Sx MACRO SYNTAX .
For general use in macro lines, these characters can either be escaped
with a non-breaking space
.Pq Sq \e&
or, if applicable, an appropriate escape sequence can be used.
.Ss Special Characters
Special characters may occur in both macro and free-form lines.
Sequences begin with the escape character
.Sq \e
followed by either an open-parenthesis
.Sq \&(
for two-character sequences; an open-bracket
.Sq \&[
for n-character sequences (terminated at a close-bracket
.Sq \&] ) ;
or a single one-character sequence.
See
.Xr mandoc_char 7
for a complete list.
Examples include
.Sq \e(em
.Pq em-dash
and
.Sq \ee
.Pq back-slash .
.Ss Text Decoration
Terms may be text-decorated using the
.Sq \ef
escape followed by an indicator: B (bold), I, (italic), R (Roman), or P
(revert to previous mode):
.Pp
.D1 \efBbold\efR \efIitalic\efP
.Pp
A numerical representation 3, 2, or 1 (bold, italic, and Roman,
respectively) may be used instead.
A text decoration is valid within
the current font scope only: if a macro opens a font scope alongside
its own scope, such as
.Sx \&Bf
.Cm \&Sy ,
in-scope invocations of
.Sq \ef
are only valid within the font scope of the macro.
If
.Sq \ef
is specified outside of any font scope, such as in unenclosed, free-form
text, it will affect the remainder of the document.
.Pp
Note this form is
.Em not
recommended for
.Nm ,
which encourages semantic annotation.
.Ss Predefined Strings
Historically,
.Xr groff 1
also defined a set of package-specific
.Dq predefined strings ,
which, like
.Sx Special Characters ,
mark special output characters and strings by way of input codes.
Predefined strings are escaped with the slash-asterisk,
.Sq \e* :
single-character
.Sq \e*X ,
two-character
.Sq \e*(XX ,
and N-character
.Sq \e*[N] .
See
.Xr mandoc_char 7
for a complete list.
Examples include
.Sq \e*(Am
.Pq ampersand
and
.Sq \e*(Ba
.Pq vertical bar .
.Ss Whitespace
Whitespace consists of the space character.
In free-form lines, whitespace is preserved within a line; un-escaped
trailing spaces are stripped from input (unless in a literal context).
Blank free-form lines, which may include whitespace, are only permitted
within literal contexts.
.Pp
In macro lines, whitespace delimits arguments and is discarded.
If arguments are quoted, whitespace within the quotes is retained.
.Ss Quotation
Macro arguments may be quoted with double-quotes to group
space-delimited terms or to retain blocks of whitespace.
A quoted argument begins with a double-quote preceded by whitespace.
The next double-quote not pair-wise adjacent to another double-quote
terminates the literal, regardless of surrounding whitespace.
.Pp
Note that any quoted text, even if it would cause a macro invocation
when unquoted, is considered literal text.
Thus, the following produces
.Sq Op "Fl a" :
.Bd -literal -offset indent
\&.Op "Fl a"
.Ed
.Pp
In free-form mode, quotes are regarded as opaque text.
.Ss Dates
There are several macros in
.Nm
that require a date argument.
The canonical form for dates is the American format:
.Pp
.D1 Cm Month Day , Year
.Pp
The
.Cm Day
value is an optionally zero-padded numeral.
The
.Cm Month
value is the full month name.
The
.Cm Year
value is the full four-digit year.
.Pp
Reduced form dates are broken-down canonical form dates:
.Pp
.D1 Cm Month , Year
.D1 Cm Year
.Pp
Some examples of valid dates follow:
.Pp
.D1 "May, 2009" Pq reduced form
.D1 "2009" Pq reduced form
.D1 "May 20, 2009" Pq canonical form
.Ss Scaling Widths
Many macros support scaled widths for their arguments, such as
stipulating a two-inch list indentation with the following:
.Bd -literal -offset indent
\&.Bl -tag -width 2i
.Ed
.Pp
The syntax for scaled widths is
.Sq Li [+-]?[0-9]*.[0-9]*[:unit:] ,
where a decimal must be preceded or proceeded by at least one digit.
Negative numbers, while accepted, are truncated to zero.
The following scaling units are accepted:
.Pp
.Bl -tag -width Ds -offset indent -compact
.It c
centimetre
.It i
inch
.It P
pica (~1/6 inch)
.It p
point (~1/72 inch)
.It f
synonym for
.Sq u
.It v
default vertical span
.It m
width of rendered
.Sq m
.Pq em
character
.It n
width of rendered
.Sq n
.Pq en
character
.It u
default horizontal span
.It M
mini-em (~1/100 em)
.El
.Pp
Using anything other than
.Sq m ,
.Sq n ,
.Sq u ,
or
.Sq v
is necessarily non-portable across output media.
See
.Sx COMPATIBILITY .
.Ss Sentence Spacing
When composing a manual, make sure that your sentences end at the end of
a line.
By doing so, front-ends will be able to apply the proper amount of
spacing after the end of sentence (unescaped) period, exclamation mark,
or question mark followed by zero or more non-sentence closing
delimiters (
.Ns Sq \&) ,
.Sq \&] ,
.Sq \&' ,
.Sq \&" ) .
.Pp
The proper spacing is also intelligently preserved if a sentence ends at
the boundary of a macro line, e.g.,
.Pp
.D1 \&Xr mandoc 1 \.
.D1 \&Fl T \&Ns \&Cm ascii \.
.Sh MANUAL STRUCTURE
A well-formed
.Nm
document consists of a document prologue followed by one or more
sections.
.Pp
The prologue, which consists of the
.Sx \&Dd ,
.Sx \&Dt ,
and
.Sx \&Os
macros in that order, is required for every document.
.Pp
The first section (sections are denoted by
.Sx \&Sh )
must be the NAME section, consisting of at least one
.Sx \&Nm
followed by
.Sx \&Nd .
.Pp
Following that, convention dictates specifying at least the
.Em SYNOPSIS
and
.Em DESCRIPTION
sections, although this varies between manual sections.
.Pp
The following is a well-formed skeleton
.Nm
file:
.Bd -literal -offset indent
\&.Dd $\&Mdocdate$
\&.Dt mdoc 7
\&.Os
\&.Sh NAME
\&.Nm foo
\&.Nd a description goes here
\&.\e\*q The next is for sections 2, 3, & 9 only.
\&.\e\*q .Sh LIBRARY
\&.Sh SYNOPSIS
\&.Nm foo
\&.Op Fl options
\&.Ar
\&.Sh DESCRIPTION
The
\&.Nm
utility processes files ...
\&.\e\*q .Sh IMPLEMENTATION NOTES
\&.\e\*q The next is for sections 2, 3, & 9 only.
\&.\e\*q .Sh RETURN VALUES
\&.\e\*q The next is for sections 1, 6, 7, & 8 only.
\&.\e\*q .Sh ENVIRONMENT
\&.\e\*q .Sh FILES
\&.\e\*q The next is for sections 1 & 8 only.
\&.\e\*q .Sh EXIT STATUS
\&.\e\*q .Sh EXAMPLES
\&.\e\*q The next is for sections 1, 4, 6, 7, & 8 only.
\&.\e\*q .Sh DIAGNOSTICS
\&.\e\*q The next is for sections 2, 3, & 9 only.
\&.\e\*q .Sh ERRORS
\&.\e\*q .Sh SEE ALSO
\&.\e\*q .Xr foobar 1
\&.\e\*q .Sh STANDARDS
\&.\e\*q .Sh HISTORY
\&.\e\*q .Sh AUTHORS
\&.\e\*q .Sh CAVEATS
\&.\e\*q .Sh BUGS
\&.\e\*q .Sh SECURITY CONSIDERATIONS
.Ed
.Pp
The sections in a
.Nm
document are conventionally ordered as they appear above.
Sections should be composed as follows:
.Bl -ohang -offset Ds
.It Em NAME
The name(s) and a one-line description of the documented material.
The syntax for this as follows:
.Bd -literal -offset indent
\&.Nm name0
\&.Nm name1
\&.Nm name2
\&.Nd a one-line description
.Ed
.Pp
The
.Sx \&Nm
macro(s) must precede the
.Sx \&Nd
macro.
.Pp
See
.Sx \&Nm
and
.Sx \&Nd .
.It Em 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:
.Bd -literal -offset indent
\&.Lb libarm
.Ed
.Pp
See
.Sx \&Lb .
.It Em SYNOPSIS
Documents the utility invocation syntax, function call syntax, or device
configuration.
.Pp
For the first, utilities (sections 1, 6, and 8), this is
generally structured as follows:
.Bd -literal -offset indent
\&.Nm foo
\&.Op Fl v
\&.Op Fl o Ar file
\&.Op Ar
\&.Nm bar
\&.Op Fl v
\&.Op Fl o Ar file
\&.Op Ar
.Ed
.Pp
For the second, function calls (sections 2, 3, 9):
.Bd -literal -offset indent
\&.Vt extern const char *global;
\&.In header.h
\&.Ft "char *"
\&.Fn foo "const char *src"
\&.Ft "char *"
\&.Fn bar "const char *src"
.Ed
.Pp
And for the third, configurations (section 4):
.Bd -literal -offset indent
\&.Cd \*qit* at isa? port 0x2e\*q
\&.Cd \*qit* at isa? port 0x4e\*q
.Ed
.Pp
Manuals not in these sections generally don't need a
.Em SYNOPSIS .
.Pp
Some macros are displayed differently in the
.Em SYNOPSIS
section, particularly
.Sx \&Nm ,
.Sx \&Cd ,
.Sx \&Fd ,
.Sx \&Fn ,
.Sx \&Fo ,
.Sx \&In ,
.Sx \&Vt ,
and
.Sx \&Ft .
All of these macros are output on their own line.
If two such dissimilar macros are pair-wise invoked (except for
.Sx \&Ft
before
.Sx \&Fo
or
.Sx \&Fn ) ,
they are separated by a vertical space, unless in the case of
.Sx \&Fo ,
.Sx \&Fn ,
and
.Sx \&Ft ,
which are always separated by vertical space.
.Pp
When text and macros following an
.Sx \&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
.Sx \&Nm
macro, up to the next
.Sx \&Nm ,
.Sx \&Sh ,
or
.Sx \&Ss
macro or the end of an enclosing block, whichever comes first.
.It Em DESCRIPTION
This expands upon the brief, one-line description in
.Em NAME .
It usually contains a break-down of the options (if documenting a
command), such as:
.Bd -literal -offset indent
The arguments are as follows:
\&.Bl \-tag \-width Ds
\&.It Fl v
Print verbose information.
\&.El
.Ed
.Pp
Manuals not documenting a command won't include the above fragment.
.It Em 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.
.It Em RETURN VALUES
This section is the dual of
.Em EXIT STATUS ,
which is used for commands.
It documents the return values of functions in sections 2, 3, and 9.
.Pp
See
.Sx \&Rv .
.It Em ENVIRONMENT
Lists the environment variables used by the utility,
and explains the syntax and semantics of their values.
The
.Xr environ 7
manual provides examples of typical content and formatting.
.Pp
See
.Sx \&Ev .
.It Em 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.).
.Pp
See
.Sx \&Pa .
.It Em EXIT STATUS
Command exit status for section 1, 6, and 8 manuals.
This section is the dual of
.Em RETURN VALUES ,
which is used for functions.
Historically, this information was described in
.Em DIAGNOSTICS ,
a practise that is now discouraged.
.Pp
See
.Sx \&Ex .
.It Em EXAMPLES
Example usages.
This often contains snippets of well-formed, well-tested invocations.
Make doubly sure that your examples work properly!
.It Em DIAGNOSTICS
Documents error conditions.
This is most useful in section 4 manuals.
Historically, this section was used in place of
.Em EXIT STATUS
for manuals in sections 1, 6, and 8; however, this practise is
discouraged.
.Pp
See
.Sx \&Bl
.Fl diag .
.It Em ERRORS
Documents error handling in sections 2, 3, and 9.
.Pp
See
.Sx \&Er .
.It Em 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.
.Pp
See
.Sx \&Xr .
.It Em STANDARDS
References any standards implemented or used.
If not adhering to any standards, the
.Em HISTORY
section should be used instead.
.Pp
See
.Sx \&St .
.It Em HISTORY
The history of any manual without a
.Em STANDARDS
section should be described in this section.
.It Em AUTHORS
Credits to authors, if applicable, should appear in this section.
Authors should generally be noted by both name and email address.
.Pp
See
.Sx \&An .
.It Em CAVEATS
Common misuses and misunderstandings should be explained
in this section.
.It Em BUGS
Known bugs, limitations and work-arounds should be described
in this section.
.It Em SECURITY CONSIDERATIONS
Documents any security precautions that operators should consider.
.El
.Sh MACRO SYNTAX
Macros are one to three three characters in length and begin with a
control character,
.Sq \&. ,
at the beginning of the line.
An arbitrary amount of whitespace may sit between the control character
and the macro name.
Thus, the following are equivalent:
.Bd -literal -offset indent
\&.Pp
\&.\ \ \ \&Pp
.Ed
.Pp
The syntax of a macro depends on its classification.
In this section,
.Sq \-arg
refers to macro arguments, which may be followed by zero or more
.Sq parm
parameters;
.Sq \&Yo
opens the scope of a macro; and if specified,
.Sq \&Yc
closes it out.
.Pp
The
.Em Callable
column indicates that the macro may be called subsequent to the initial
line-macro.
If a macro is not callable, then its invocation after the initial line
macro is interpreted as opaque text, such that
.Sq \&.Fl \&Sh
produces
.Sq Fl \&Sh .
.Pp
The
.Em Parsed
column indicates whether the macro may be followed by further
(ostensibly callable) macros.
If a macro is not parsed, subsequent macro invocations on the line
will be interpreted as opaque text.
.Pp
The
.Em Scope
column, if applicable, describes closure rules.
.Ss Block full-explicit
Multi-line scope closed by an explicit closing macro.
All macros contains bodies; only
.Sx \&Bf
contains a head.
.Bd -literal -offset indent
\&.Yo \(lB\-arg \(lBparm...\(rB\(rB \(lBhead...\(rB
\(lBbody...\(rB
\&.Yc
.Ed
.Pp
.Bl -column -compact -offset indent "MacroX" "CallableX" "ParsedX" "closed by XXX"
.It Em Macro Ta Em Callable Ta Em Parsed Ta Em Scope
.It Sx \&Bd  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Ed
.It Sx \&Bf  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Ef
.It Sx \&Bk  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Ek
.It Sx \&Bl  Ta    \&No     Ta    \&No     Ta    closed by Sx \&El
.It Sx \&Ed  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Bd
.It Sx \&Ef  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Bf
.It Sx \&Ek  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Bk
.It Sx \&El  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Bl
.El
.Ss Block full-implicit
Multi-line scope closed by end-of-file or implicitly by another macro.
All macros have bodies; some
.Po
.Sx \&It Fl bullet ,
.Fl hyphen ,
.Fl dash ,
.Fl enum ,
.Fl item
.Pc
don't have heads; only one
.Po
.Sx \&It
in
.Sx \&Bl Fl column
.Pc
has multiple heads.
.Bd -literal -offset indent
\&.Yo \(lB\-arg \(lBparm...\(rB\(rB \(lBhead... \(lBTa head...\(rB\(rB
\(lBbody...\(rB
.Ed
.Pp
.Bl -column -compact -offset indent "MacroX" "CallableX" "ParsedX" "closed by XXXXXXXXXXX"
.It Em Macro Ta Em Callable Ta Em Parsed Ta Em Scope
.It Sx \&It  Ta    \&No     Ta    Yes      Ta    closed by Sx \&It , Sx \&El
.It Sx \&Nd  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Sh
.It Sx \&Nm  Ta    \&No     Ta  Yes Ta closed by Sx \&Nm , Sx \&Sh , Sx \&Ss
.It Sx \&Sh  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Sh
.It Sx \&Ss  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Sh , Sx \&Ss
.El
.Pp
Note that the
.Sx \&Nm
macro is a
.Sx Block full-implicit
macro only when invoked as the first macro
in a
.Em SYNOPSIS
section line, else it is
.Sx In-line .
.Ss 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
.Po
.Sx \&Fo ,
.Sx \&Eo
.Pc
and/or tail
.Pq Sx \&Ec .
.Bd -literal -offset indent
\&.Yo \(lB\-arg \(lBparm...\(rB\(rB \(lBhead...\(rB
\(lBbody...\(rB
\&.Yc \(lBtail...\(rB

\&.Yo \(lB\-arg \(lBparm...\(rB\(rB \(lBhead...\(rB \
\(lBbody...\(rB \&Yc \(lBtail...\(rB
.Ed
.Pp
.Bl -column "MacroX" "CallableX" "ParsedX" "closed by XXXX" -compact -offset indent
.It Em Macro Ta Em Callable Ta Em Parsed Ta Em Scope
.It Sx \&Ac  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Ao
.It Sx \&Ao  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Ac
.It Sx \&Bc  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Bo
.It Sx \&Bo  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Bc
.It Sx \&Brc Ta    Yes      Ta    Yes      Ta    opened by Sx \&Bro
.It Sx \&Bro Ta    Yes      Ta    Yes      Ta    closed by Sx \&Brc
.It Sx \&Dc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Do
.It Sx \&Do  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Dc
.It Sx \&Ec  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Eo
.It Sx \&Eo  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Ec
.It Sx \&Fc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Fo
.It Sx \&Fo  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Fc
.It Sx \&Oc  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Oo
.It Sx \&Oo  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Oc
.It Sx \&Pc  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Po
.It Sx \&Po  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Pc
.It Sx \&Qc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Oo
.It Sx \&Qo  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Oc
.It Sx \&Re  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Rs
.It Sx \&Rs  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Re
.It Sx \&Sc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&So
.It Sx \&So  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Sc
.It Sx \&Xc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Xo
.It Sx \&Xo  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Xc
.El
.Ss Block partial-implicit
Like block full-implicit, but with single-line scope closed by
.Sx Reserved Characters
or end of line.
.Bd -literal -offset indent
\&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBbody...\(rB \(lBres...\(rB
.Ed
.Pp
.Bl -column "MacroX" "CallableX" "ParsedX" -compact -offset indent
.It Em Macro Ta Em Callable Ta Em Parsed
.It Sx \&Aq  Ta    Yes      Ta    Yes
.It Sx \&Bq  Ta    Yes      Ta    Yes
.It Sx \&Brq Ta    Yes      Ta    Yes
.It Sx \&D1  Ta    \&No     Ta    \&Yes
.It Sx \&Dl  Ta    \&No     Ta    Yes
.It Sx \&Dq  Ta    Yes      Ta    Yes
.It Sx \&Op  Ta    Yes      Ta    Yes
.It Sx \&Pq  Ta    Yes      Ta    Yes
.It Sx \&Ql  Ta    Yes      Ta    Yes
.It Sx \&Qq  Ta    Yes      Ta    Yes
.It Sx \&Sq  Ta    Yes      Ta    Yes
.It Sx \&Vt  Ta    Yes      Ta    Yes
.El
.Pp
Note that the
.Sx \&Vt
macro is a
.Sx Block partial-implicit
only when invoked as the first macro
in a
.Em SYNOPSIS
section line, else it is
.Sx In-line .
.Ss In-line
Closed by
.Sx Reserved Characters ,
end of line, fixed argument lengths, and/or subsequent macros.
In-line macros have only text children.
If a number (or inequality) of arguments is
.Pq n ,
then the macro accepts an arbitrary number of arguments.
.Bd -literal -offset indent
\&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBargs...\(rB \(lbres...\(rb

\&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBargs...\(rB Yc...

\&.Yo \(lB\-arg \(lBval...\(rB\(rB arg0 arg1 argN
.Ed
.Pp
.Bl -column "MacroX" "CallableX" "ParsedX" "Arguments" -compact -offset indent
.It Em Macro Ta Em Callable Ta Em Parsed Ta Em Arguments
.It Sx \&%A  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%B  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%C  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%D  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%I  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%J  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%N  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%O  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%P  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%Q  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%R  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%T  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%U  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&%V  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&Ad  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&An  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Ap  Ta    Yes      Ta    Yes      Ta    0
.It Sx \&Ar  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&At  Ta    Yes      Ta    Yes      Ta    1
.It Sx \&Bsx Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Bt  Ta    \&No     Ta    \&No     Ta    0
.It Sx \&Bx  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Cd  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Cm  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Db  Ta    \&No     Ta    \&No     Ta    1
.It Sx \&Dd  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Dt  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Dv  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Dx  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Em  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&En  Ta    \&No     Ta    \&No     Ta    0
.It Sx \&Er  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Es  Ta    \&No     Ta    \&No     Ta    0
.It Sx \&Ev  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Ex  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Fa  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Fd  Ta    \&No     Ta    \&No     Ta    >0
.It Sx \&Fl  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Fn  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Fr  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Ft  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Fx  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Hf  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Ic  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&In  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Lb  Ta    \&No     Ta    \&No     Ta    1
.It Sx \&Li  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Lk  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Lp  Ta    \&No     Ta    \&No     Ta    0
.It Sx \&Ms  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Mt  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Nm  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&No  Ta    Yes      Ta    Yes      Ta    0
.It Sx \&Ns  Ta    Yes      Ta    Yes      Ta    0
.It Sx \&Nx  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Os  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Ot  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Ox  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Pa  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Pf  Ta    Yes      Ta    Yes      Ta    1
.It Sx \&Pp  Ta    \&No     Ta    \&No     Ta    0
.It Sx \&Rv  Ta    \&No     Ta    \&No     Ta    n
.It Sx \&Sm  Ta    \&No     Ta    \&No     Ta    1
.It Sx \&St  Ta    \&No     Ta    Yes      Ta    1
.It Sx \&Sx  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Sy  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Tn  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Ud  Ta    \&No     Ta    \&No     Ta    0
.It Sx \&Ux  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Va  Ta    Yes      Ta    Yes      Ta    n
.It Sx \&Vt  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&Xr  Ta    Yes      Ta    Yes      Ta    >0
.It Sx \&br  Ta    \&No     Ta    \&No     Ta    0
.It Sx \&sp  Ta    \&No     Ta    \&No     Ta    1
.El
.Sh REFERENCE
This section is a canonical reference of all macros, arranged
alphabetically.
For the scoping of individual macros, see
.Sx MACRO SYNTAX .
.Ss \&%A
Author name of an
.Sx \&Rs
block.
Multiple authors should each be accorded their own
.Sx \%%A
line.
Author names should be ordered with full or abbreviated forename(s)
first, then full surname.
.Ss \&%B
Book title of an
.Sx \&Rs
block.
This macro may also be used in a non-bibliographic context when
referring to book titles.
.Ss \&%C
Publication city or location of an
.Sx \&Rs
block.
.Pp
.Em Remarks :
this macro is not implemented in
.Xr groff 1 .
.Ss \&%D
Publication date of an
.Sx \&Rs
block.
This should follow the reduced or canonical form syntax described in
.Sx Dates .
.Ss \&%I
Publisher or issuer name of an
.Sx \&Rs
block.
.Ss \&%J
Journal name of an
.Sx \&Rs
block.
.Ss \&%N
Issue number (usually for journals) of an
.Sx \&Rs
block.
.Ss \&%O
Optional information of an
.Sx \&Rs
block.
.Ss \&%P
Book or journal page number of an
.Sx \&Rs
block.
.Ss \&%Q
Institutional author (school, government, etc.) of an
.Sx \&Rs
block.
Multiple institutional authors should each be accorded their own
.Sx \&%Q
line.
.Ss \&%R
Technical report name of an
.Sx \&Rs
block.
.Ss \&%T
Article title of an
.Sx \&Rs
block.
This macro may also be used in a non-bibliographical context when
referring to article titles.
.Ss \&%U
URI of reference document.
.Ss \&%V
Volume number of an
.Sx \&Rs
block.
.Ss \&Ac
Close an
.Sx \&Ao
block.
Does not have any tail arguments.
.Ss \&Ad
Memory address.
Do not use this for postal addresses.
.Pp
Examples:
.D1 \&.Ad [0,$]
.D1 \&.Ad 0x00000000
.Ss \&An
Author name.
Requires either the name of an author or one of the following arguments:
.Pp
.Bl -tag -width "-nosplitX" -offset indent -compact
.It Fl split
Start a new output line before each subsequent invocation of
.Sx \&An .
.It Fl nosplit
The opposite of
.Fl split .
.El
.Pp
The default is
.Fl nosplit .
The effect of selecting either of the
.Fl split
modes ends at the beginning of the
.Em AUTHORS
section.
In the
.Em AUTHORS
section, the default is
.Fl nosplit
for the first author listing and
.Fl split
for all other author listings.
.Pp
Examples:
.D1 \&.An -nosplit
.D1 \&.An Kristaps Dzonsons \&Aq kristaps@bsd.lv
.Ss \&Ao
Begin a block enclosed by angle brackets.
Does not have any head arguments.
.Pp
Examples:
.D1 \&.Fl -key= \&Ns \&Ao \&Ar val \&Ac
.Pp
See also
.Sx \&Aq .
.Ss \&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.
.Pp
Examples:
.D1 \&.Fn execve \&Ap d
.Ss \&Aq
Encloses its arguments in angle brackets.
.Pp
Examples:
.D1 \&.Fl -key= \&Ns \&Aq \&Ar val
.Pp
.Em Remarks :
this macro is often abused for rendering URIs, which should instead use
.Sx \&Lk
or
.Sx \&Mt ,
or to note pre-processor
.Dq Li #include
statements, which should use
.Sx \&In .
.Pp
See also
.Sx \&Ao .
.Ss \&Ar
Command arguments.
If an argument is not provided, the string
.Dq file ...\&
is used as a default.
.Pp
Examples:
.D1 \&.Fl o \&Ns \&Ar file1
.D1 \&.Ar
.D1 \&.Ar arg1 , arg2 .
.Ss \&At
Formats an AT&T version.
Accepts one optional argument:
.Pp
.Bl -tag -width "v[1-7] | 32vX" -offset indent -compact
.It Cm v[1-7] | 32v
A version of
.At .
.It Cm V[.[1-4]]?
A version of
.At V .
.El
.Pp
Note that these arguments do not begin with a hyphen.
.Pp
Examples:
.D1 \&.At
.D1 \&.At V.1
.Pp
See also
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.Ss \&Bc
Close a
.Sx \&Bo
block.
Does not have any tail arguments.
.Ss \&Bd
Begin a display block.
Its syntax is as follows:
.Bd -ragged -offset indent
.Pf \. Sx \&Bd
.Fl Ns Ar type
.Op Fl offset Ar width
.Op Fl compact
.Ed
.Pp
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 free-form text lines.
By default, a display block is preceded by a vertical space.
.Pp
The
.Ar type
must be one of the following:
.Bl -tag -width 13n -offset indent
.It Fl centered
Centre-justify each line.
Using this display type is not recommended; many
.Nm
implementations render it poorly.
.It Fl filled
Left- and right-justify the block.
.It Fl literal
Do not justify the block at all.
Preserve white space as it appears in the input.
.It Fl ragged
Only left-justify the block.
.It Fl unfilled
An alias for
.Fl literal .
.El
.Pp
The
.Ar type
must be provided first.
Additional arguments may follow:
.Bl -tag -width 13n -offset indent
.It Fl offset Ar width
Indent the display by the
.Ar width ,
which may be one of the following:
.Bl -item
.It
One of the pre-defined strings
.Cm indent ,
the width of standard indentation;
.Cm indent-two ,
twice
.Cm indent ;
.Cm left ,
which has no effect;
.Cm right ,
which justifies to the right margin; or
.Cm center ,
which aligns around an imagined centre axis.
.It
A macro invocation, which selects a predefined width
associated with that macro.
The most popular is the imaginary macro
.Ar \&Ds ,
which resolves to
.Sy 6n .
.It
A width using the syntax described in
.Sx Scaling Widths .
.It
An arbitrary string, which indents by the length of this string.
.El
.Pp
When the argument is missing,
.Fl offset
is ignored.
.It Fl compact
Do not assert vertical space before the display.
.El
.Pp
Examples:
.Bd -literal -offset indent
\&.Bd \-literal \-offset indent \-compact
   Hello       world.
\&.Ed
.Ed
.Pp
See also
.Sx \&D1
and
.Sx \&Dl .
.Ss \&Bf
Change the font mode for a scoped block of text.
Its syntax is as follows:
.Bd -ragged -offset indent
.Pf \. Sx \&Bf
.Oo
.Fl emphasis | literal | symbolic |
.Cm \&Em | \&Li | \&Sy
.Oc
.Ed
.Pp
The
.Fl emphasis
and
.Cm \&Em
argument are equivalent, as are
.Fl symbolic
and
.Cm \&Sy,
and
.Fl literal
and
.Cm \&Li .
Without an argument, this macro does nothing.
The font mode continues until broken by a new font mode in a nested
scope or
.Sx \&Ef
is encountered.
.Pp
See also
.Sx \&Li ,
.Sx \&Ef ,
.Sx \&Em ,
and
.Sx \&Sy .
.Ss \&Bk
Keep the output generated from each macro input line together
on one single output line.
Line breaks in free-form text lines are unaffected.
The syntax is as follows:
.Pp
.D1 Pf \. Sx \&Bk Fl words
.Pp
The
.Fl words
argument is required; additional arguments are ignored.
.Pp
The following example will not break within each
.Sx \&Op
macro line:
.Bd -literal -offset indent
\&.Bk \-words
\&.Op Fl f Ar flags
\&.Op Fl o Ar output
\&.Ek
.Ed
.Pp
Be careful in using over-long lines within a keep block!
Doing so will clobber the right margin.
.Ss \&Bl
Begin a list.
Lists consist of items started by the
.Sx \&It
macro, containing a head or a body or both.
The list syntax is as follows:
.Bd -ragged -offset indent
.Pf \. Sx \&Bl
.Fl Ns Ar type
.Op Fl width Ar val
.Op Fl offset Ar val
.Op Fl compact
.Op HEAD ...
.Ed
.Pp
The list
.Ar type
is mandatory and must be specified first.
The
.Fl width
and
.Fl offset
arguments accept
.Sx Scaling Widths
or use the length of the given string.
The
.Fl offset
is a global indentation for the whole list, affecting both item heads
and bodies.
For those list types supporting it, the
.Fl width
argument requests an additional indentation of item bodies,
to be added to the
.Fl offset .
Unless the
.Fl compact
argument is specified, list entries are separated by vertical space.
.Pp
A list must specify one of the following list types:
.Bl -tag -width 12n -offset indent
.It Fl 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
.Fl width
argument.
.It Fl column
A columnated list.
The
.Fl width
argument has no effect; instead, each argument specifies the width
of one column, using either the
.Sx Scaling Widths
syntax or the string length of the argument.
If the first line of the body of a
.Fl column
list is not an
.Sx \&It
macro line,
.Sx \&It
contexts spanning one input line each are implied until an
.Sx \&It
macro line is encountered, at which point items start being interpreted as
described in the
.Sx \&It
documentation.
.It Fl dash
Like
.Fl bullet ,
except that dashes are used in place of bullets.
.It Fl diag
Like
.Fl inset ,
except that item heads are not parsed for macro invocations.
.\" but with additional formatting to the head.
.It Fl enum
A numbered list.
Formatted like
.Fl bullet ,
except that cardinal numbers are used in place of bullets,
starting at 1.
.It Fl hang
Like
.Fl tag ,
except that the first lines of item bodies are not indented, but follow
the item heads like in
.Fl inset
lists.
.It Fl hyphen
Synonym for
.Fl dash .
.It Fl inset
Item bodies follow items heads on the same line, using normal inter-word
spacing.
Bodies are not indented, and the
.Fl width
argument is ignored.
.It Fl item
No item heads can be specified, and none are printed.
Bodies are not indented, and the
.Fl width
argument is ignored.
.It Fl ohang
Item bodies start on the line following item heads and are not indented.
The
.Fl width
argument is ignored.
.It Fl tag
Item bodies are indented according to the
.Fl 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.
.El
.Pp
See also
.Sx \&El
and
.Sx \&It .
.Ss \&Bo
Begin a block enclosed by square brackets.
Does not have any head arguments.
.Pp
Examples:
.Bd -literal -offset indent -compact
\&.Bo 1 ,
\&.Dv BUFSIZ \&Bc
.Ed
.Pp
See also
.Sx \&Bq .
.Ss \&Bq
Encloses its arguments in square brackets.
.Pp
Examples:
.D1 \&.Bq 1 , \&Dv BUFSIZ
.Pp
.Em Remarks :
this macro is sometimes abused to emulate optional arguments for
commands; the correct macros to use for this purpose are
.Sx \&Op ,
.Sx \&Oo ,
and
.Sx \&Oc .
.Pp
See also
.Sx \&Bo .
.Ss \&Brc
Close a
.Sx \&Bro
block.
Does not have any tail arguments.
.Ss \&Bro
Begin a block enclosed by curly braces.
Does not have any head arguments.
.Pp
Examples:
.Bd -literal -offset indent -compact
\&.Bro 1 , ... ,
\&.Va n \&Brc
.Ed
.Pp
See also
.Sx \&Brq .
.Ss \&Brq
Encloses its arguments in curly braces.
.Pp
Examples:
.D1 \&.Brq 1 , ... , \&Va n
.Pp
See also
.Sx \&Bro .
.Ss \&Bsx
Format the BSD/OS version provided as an argument, or a default value if
no argument is provided.
.Pp
Examples:
.D1 \&.Bsx 1.0
.D1 \&.Bsx
.Pp
See also
.Sx \&At ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.Ss \&Bt
Prints
.Dq is currently in beta test.
.Ss \&Bx
Format the BSD version provided as an argument, or a default value if no
argument is provided.
.Pp
Examples:
.D1 \&.Bx 4.4
.D1 \&.Bx
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.Ss \&Cd
Kernel configuration declaration.
This denotes strings accepted by
.Xr config 8 .
.Pp
Examples:
.D1 \&.Cd device le0 at scode?
.Pp
.Em Remarks :
this macro is commonly abused by using quoted literals to retain
whitespace and align consecutive
.Sx \&Cd
declarations.
This practise is discouraged.
.Ss \&Cm
Command modifiers.
Useful when specifying configuration options or keys.
.Pp
Examples:
.D1 \&.Cm ControlPath
.D1 \&.Cm ControlMaster
.Pp
See also
.Sx \&Fl .
.Ss \&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.
.Pp
Examples:
.D1 \&.D1 \&Fl abcdefgh
.Pp
See also
.Sx \&Bd
and
.Sx \&Dl .
.Ss \&Db
Switch debugging mode.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Db Cm on | off
.Pp
This macro is ignored by
.Xr mandoc 1 .
.Ss \&Dc
Close a
.Sx \&Do
block.
Does not have any tail arguments.
.Ss \&Dd
Document date.
This is the mandatory first macro of any
.Nm
manual.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Dd Op Ar date
.Pp
The
.Ar date
may be either
.Ar $\&Mdocdate$ ,
which signifies the current manual revision date dictated by
.Xr cvs 1 ,
or instead a valid canonical date as specified by
.Sx Dates .
If a date does not conform or is empty, the current date is used.
.Pp
Examples:
.D1 \&.Dd $\&Mdocdate$
.D1 \&.Dd $\&Mdocdate: July 21 2007$
.D1 \&.Dd July 21, 2007
.Pp
See also
.Sx \&Dt
and
.Sx \&Os .
.Ss \&Dl
One-line intended display.
This is formatted as literal text and is useful for commands and
invocations.
It is followed by a newline.
.Pp
Examples:
.D1 \&.Dl % mandoc mdoc.7 \e(ba less
.Pp
See also
.Sx \&Bd
and
.Sx \&D1 .
.Ss \&Do
Begin a block enclosed by double quotes.
Does not have any head arguments.
.Pp
Examples:
.Bd -literal -offset indent -compact
\&.Do
April is the cruellest month
\&.Dc
\e(em T.S. Eliot
.Ed
.Pp
See also
.Sx \&Dq .
.Ss \&Dq
Encloses its arguments in
.Dq typographic
double-quotes.
.Pp
Examples:
.Bd -literal -offset indent -compact
\&.Dq April is the cruellest month
\e(em T.S. Eliot
.Ed
.Pp
See also
.Sx \&Qq ,
.Sx \&Sq ,
and
.Sx \&Do .
.Ss \&Dt
Document title.
This is the mandatory second macro of any
.Nm
file.
Its syntax is as follows:
.Bd -ragged -offset indent
.Pf \. Sx \&Dt
.Oo
.Ar title
.Oo
.Ar section
.Op Ar volume | arch
.Oc
.Oc
.Ed
.Pp
Its arguments are as follows:
.Bl -tag -width Ds -offset Ds
.It Ar title
The document's title (name), defaulting to
.Dq UNKNOWN
if unspecified.
It should be capitalised.
.It Ar section
The manual section.
This may be one of
.Ar 1
.Pq utilities ,
.Ar 2
.Pq system calls ,
.Ar 3
.Pq libraries ,
.Ar 3p
.Pq Perl libraries ,
.Ar 4
.Pq devices ,
.Ar 5
.Pq file formats ,
.Ar 6
.Pq games ,
.Ar 7
.Pq miscellaneous ,
.Ar 8
.Pq system utilities ,
.Ar 9
.Pq kernel functions ,
.Ar X11
.Pq X Window System ,
.Ar X11R6
.Pq X Window System ,
.Ar unass
.Pq unassociated ,
.Ar local
.Pq local system ,
.Ar draft
.Pq draft manual ,
or
.Ar paper
.Pq paper .
It should correspond to the manual's filename suffix and defaults to
.Dq 1
if unspecified.
.It Ar volume
This overrides the volume inferred from
.Ar section .
This field is optional, and if specified, must be one of
.Ar USD
.Pq users' supplementary documents ,
.Ar PS1
.Pq programmers' supplementary documents ,
.Ar AMD
.Pq administrators' supplementary documents ,
.Ar SMM
.Pq system managers' manuals ,
.Ar URM
.Pq users' reference manuals ,
.Ar PRM
.Pq programmers' reference manuals ,
.Ar KM
.Pq kernel manuals ,
.Ar IND
.Pq master index ,
.Ar MMI
.Pq master index ,
.Ar LOCAL
.Pq local manuals ,
.Ar LOC
.Pq local manuals ,
or
.Ar CON
.Pq contributed manuals .
.It Ar arch
This specifies a specific relevant architecture.
If
.Ar volume
is not provided, it may be used in its place, else it may be used
subsequent that.
It, too, is optional.
It must be one of
.Ar alpha ,
.Ar amd64 ,
.Ar amiga ,
.Ar arc ,
.Ar arm ,
.Ar armish ,
.Ar aviion ,
.Ar hp300 ,
.Ar hppa ,
.Ar hppa64 ,
.Ar i386 ,
.Ar landisk ,
.Ar loongson ,
.Ar luna88k ,
.Ar mac68k ,
.Ar macppc ,
.Ar mvme68k ,
.Ar mvme88k ,
.Ar mvmeppc ,
.Ar pmax ,
.Ar sgi ,
.Ar socppc ,
.Ar sparc ,
.Ar sparc64 ,
.Ar sun3 ,
.Ar vax ,
or
.Ar zaurus .
.El
.Pp
Examples:
.D1 \&.Dt FOO 1
.D1 \&.Dt FOO 4 KM
.D1 \&.Dt FOO 9 i386
.Pp
See also
.Sx \&Dd
and
.Sx \&Os .
.Ss \&Dv
Defined variables such as preprocessor constants.
.Pp
Examples:
.D1 \&.Dv BUFSIZ
.D1 \&.Dv STDOUT_FILENO
.Pp
See also
.Sx \&Er .
.Ss \&Dx
Format the DragonFly BSD version provided as an argument, or a default
value if no argument is provided.
.Pp
Examples:
.D1 \&.Dx 2.4.1
.D1 \&.Dx
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Fx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.Ss \&Ec
Close a scope started by
.Sx \&Eo .
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Ec Op Ar TERM
.Pp
The
.Ar TERM
argument is used as the enclosure tail, for example, specifying \e(rq
will emulate
.Sx \&Dc .
.Ss \&Ed
End a display context started by
.Sx \&Bd .
.Ss \&Ef
End a font mode context started by
.Sx \&Bf .
.Ss \&Ek
End a keep context started by
.Sx \&Bk .
.Ss \&El
End a list context started by
.Sx \&Bl .
.Pp
See also
.Sx \&Bl
and
.Sx \&It .
.Ss \&Em
Denotes text that should be emphasised.
Note that this is a presentation term and should not be used for
stylistically decorating technical terms.
.Pp
Examples:
.D1 \&.Em Warnings!
.D1 \&.Em Remarks :
.Pp
See also
.Sx \&Bf ,
.Sx \&Sy ,
and
.Sx \&Li .
.Ss \&En
This macro is obsolete and not implemented in
.Xr mandoc 1 .
.Ss \&Eo
An arbitrary enclosure.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Eo Op Ar TERM
.Pp
The
.Ar TERM
argument is used as the enclosure head, for example, specifying \e(lq
will emulate
.Sx \&Do .
.Ss \&Er
Display error constants.
.Pp
Examples:
.D1 \&.Er EPERM
.D1 \&.Er ENOENT
.Pp
See also
.Sx \&Dv .
.Ss \&Es
This macro is obsolete and not implemented.
.Ss \&Ev
Environmental variables such as those specified in
.Xr environ 7 .
.Pp
Examples:
.D1 \&.Ev DISPLAY
.D1 \&.Ev PATH
.Ss \&Ex
Insert a standard sentence regarding exit values.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Ex Fl std Op Ar utility
.Pp
When
.Ar utility
is not specified, the document's name set by
.Sx \&Nm
is used.
.Pp
See also
.Sx \&Rv .
.Ss \&Fa
Function argument.
Its syntax is as follows:
.Bd -ragged -offset indent
.Pf \. Sx \&Fa
.Op Cm argtype
.Cm argname
.Ed
.Pp
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
.Sx \&Fa
macro is used in the
.Em SYNOPSIS
within
.Sx \&Fo
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
.Sx \&Fa ,
the last argument will also have a trailing comma.
.Pp
Examples:
.D1 \&.Fa \(dqconst char *p\(dq
.D1 \&.Fa \(dqint a\(dq \(dqint b\(dq \(dqint c\(dq
.D1 \&.Fa foo
.Pp
See also
.Sx \&Fo .
.Ss \&Fc
End a function context started by
.Sx \&Fo .
.Ss \&Fd
Historically used to document include files.
This usage has been deprecated in favour of
.Sx \&In .
Do not use this macro.
.Pp
See also
.Sx MANUAL STRUCTURE
and
.Sx \&In .
.Ss \&Fl
Command-line flag.
Used when listing arguments to command-line utilities.
Prints a fixed-width hyphen
.Sq \-
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.
.Pp
Examples:
.D1 \&.Fl a b c
.D1 \&.Fl \&Pf a b
.D1 \&.Fl
.D1 \&.Op \&Fl o \&Ns \&Ar file
.Pp
See also
.Sx \&Cm .
.Ss \&Fn
A function name.
Its syntax is as follows:
.Bd -ragged -offset indent
.Pf \. Ns Sx \&Fn
.Op Cm functype
.Cm funcname
.Op Oo Cm argtype Oc Cm argname
.Ed
.Pp
Function arguments are surrounded in parenthesis and
are delimited by commas.
If no arguments are specified, blank parenthesis are output.
.Pp
Examples:
.D1 \&.Fn "int funcname" "int arg0" "int arg1"
.D1 \&.Fn funcname "int arg0"
.D1 \&.Fn funcname arg0
.Bd -literal -offset indent -compact
\&.Ft functype
\&.Fn funcname
.Ed
.Pp
See also
.Sx MANUAL STRUCTURE
and
.Sx \&Ft .
.Ss \&Fo
Begin a function block.
This is a multi-line version of
.Sx \&Fn .
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Fo Cm funcname
.Pp
Invocations usually occur in the following context:
.Bd -ragged -offset indent
.Pf \. Sx \&Ft Cm functype
.br
.Pf \. Sx \&Fo Cm funcname
.br
.Pf \. Sx \&Fa Oo Cm argtype Oc Cm argname
.br
\.\.\.
.br
.Pf \. Sx \&Fc
.Ed
.Pp
A
.Sx \&Fo
scope is closed by
.Pp
See also
.Sx MANUAL STRUCTURE ,
.Sx \&Fa ,
.Sx \&Fc ,
and
.Sx \&Ft .
.Ss \&Ft
A function type.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Ft Cm functype
.Pp
Examples:
.D1 \&.Ft int
.Bd -literal -offset indent -compact
\&.Ft functype
\&.Fn funcname
.Ed
.Pp
See also
.Sx MANUAL STRUCTURE ,
.Sx \&Fn ,
and
.Sx \&Fo .
.Ss \&Fx
Format the FreeBSD version provided as an argument, or a default value
if no argument is provided.
.Pp
Examples:
.D1 \&.Fx 7.1
.D1 \&.Fx
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.Ss \&Hf
This macro is obsolete and not implemented.
.Ss \&Ic
Designate an internal or interactive command.
This is similar to
.Sx \&Cm
but used for instructions rather than values.
.Pp
Examples:
.D1 \&.Ic hash
.D1 \&.Ic alias
.Pp
Note that using
.Sx \&Bd No Fl literal
or
.Sx \&D1
is preferred for displaying code; the
.Sx \&Ic
macro is used when referring to specific instructions.
.Ss \&In
An
.Dq include
file.
In the
.Em SYNOPSIS
section (only if invoked as the line macro), the first argument is
preceded by
.Dq #include ,
the arguments is enclosed in angle brackets.
.Pp
Examples:
.D1 \&.In sys/types
.Pp
See also
.Sx MANUAL STRUCTURE .
.Ss \&It
A list item.
The syntax of this macro depends on the list type.
.Pp
Lists
of type
.Fl hang ,
.Fl ohang ,
.Fl inset ,
and
.Fl diag
have the following syntax:
.Pp
.D1 Pf \. Sx \&It Cm args
.Pp
Lists of type
.Fl bullet ,
.Fl dash ,
.Fl enum ,
.Fl hyphen
and
.Fl item
have the following syntax:
.Pp
.D1 Pf \. Sx \&It
.Pp
with subsequent lines interpreted within the scope of the
.Sx \&It
until either a closing
.Sx \&El
or another
.Sx \&It .
.Pp
The
.Fl tag
list has the following syntax:
.Pp
.D1 Pf \. Sx \&It Op Cm args
.Pp
Subsequent lines are interpreted as with
.Fl bullet
and family.
The line arguments correspond to the list's left-hand side; body
arguments correspond to the list's contents.
.Pp
The
.Fl column
list is the most complicated.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&It Op Cm args
.Pp
The
.Cm args
are phrases, a mix of macros and text corresponding to a line column,
delimited by tabs or the special
.Sq \&Ta
pseudo-macro.
Lines subsequent the
.Sx \&It
are interpreted within the scope of the last phrase.
Calling the pseudo-macro
.Sq \&Ta
will open a new phrase scope (this must occur on a macro line to be
interpreted as a macro).
Note that the tab phrase delimiter may only be used within the
.Sx \&It
line itself.
Subsequent this, only the
.Sq \&Ta
pseudo-macro may be used to delimit phrases.
Furthermore, note that quoted sections propagate over tab-delimited
phrases on an
.Sx \&It ,
for example,
.Pp
.D1 .It \(dqcol1 ; <TAB> col2 ;\(dq \&;
.Pp
will preserve the semicolon whitespace except for the last.
.Pp
See also
.Sx \&Bl .
.Ss \&Lb
Specify a library.
The syntax is as follows:
.Pp
.D1 Pf \. Sx \&Lb Cm library
.Pp
The
.Cm library
parameter may be a system library, such as
.Cm libz
or
.Cm 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
.Em SYNOPSIS
section as described in
.Sx MANUAL STRUCTURE .
.Pp
Examples:
.D1 \&.Lb libz
.D1 \&.Lb mdoc
.Ss \&Li
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.
.Pp
See also
.Sx \&Bf ,
.Sx \&Sy ,
and
.Sx \&Em .
.Ss \&Lk
Format a hyperlink.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Lk Cm uri Op Cm name
.Pp
Examples:
.D1 \&.Lk http://bsd.lv "The BSD.lv Project"
.D1 \&.Lk http://bsd.lv
.Pp
See also
.Sx \&Mt .
.Ss \&Lp
Synonym for
.Sx \&Pp .
.Ss \&Ms
Display a mathematical symbol.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Ms Cm symbol
.Pp
Examples:
.D1 \&.Ms sigma
.D1 \&.Ms aleph
.Ss \&Mt
Format a
.Dq mailto:
hyperlink.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Mt Cm address
.Pp
Examples:
.D1 \&.Mt discuss@manpages.bsd.lv
.Ss \&Nd
A one-line description of the manual's content.
This may only be invoked in the
.Em SYNOPSIS
section subsequent the
.Sx \&Nm
macro.
.Pp
Examples:
.D1 \&.Sx \&Nd mdoc language reference
.D1 \&.Sx \&Nd format and display UNIX manuals
.Pp
The
.Sx \&Nd
macro technically accepts child macros and terminates with a subsequent
.Sx \&Sh
invocation.
Do not assume this behaviour: some
.Xr whatis 1
database generators are not smart enough to parse more than the line
arguments and will display macros verbatim.
.Pp
See also
.Sx \&Nm .
.Ss \&Nm
The name of the manual page, or \(em in particular in section 1, 6,
and 8 pages \(em of an additional command or feature documented in
the manual page.
When first invoked, the
.Sx \&Nm
macro expects a single argument, the name of the manual page.
Usually, the first invocation happens in the
.Em 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
.Sx \&Nm
macro uses
.Sx Block full-implicit
semantics when invoked as the first macro on an input line in the
.Em SYNOPSIS
section; otherwise, it uses ordinary
.Sx In-line
semantics.
.Pp
Examples:
.Bd -literal -offset indent
\&.Sh SYNOPSIS
\&.Nm cat
\&.Op Fl benstuv
\&.Op Ar
.Ed
.Pp
In the
.Em SYNOPSIS
of section 2, 3 and 9 manual pages, use the
.Sx \&Fn
macro rather than
.Sx \&Nm
to mark up the name of the manual page.
.Ss \&No
A
.Dq noop
macro used to terminate prior macro contexts.
.Pp
Examples:
.D1 \&.Sx \&Fl ab \&No cd \&Fl ef
.Ss \&Ns
Suppress a space.
Following invocation, text is interpreted as free-form text until a
macro is encountered.
.Pp
Examples:
.D1 \&.Fl o \&Ns \&Ar output
.Pp
See also
.Sx \&No
and
.Sx \&Sm .
.Ss \&Nx
Format the NetBSD version provided as an argument, or a default value if
no argument is provided.
.Pp
Examples:
.D1 \&.Nx 5.01
.D1 \&.Nx
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.Ss \&Oc
Close multi-line
.Sx \&Oo
context.
.Ss \&Oo
Multi-line version of
.Sx \&Op .
.Pp
Examples:
.Bd -literal -offset indent -compact
\&.Oo
\&.Op Fl flag Ns Ar value
\&.Oc
.Ed
.Ss \&Op
Command-line option.
Used when listing options to command-line utilities.
Prints the argument(s) in brackets.
.Pp
Examples:
.D1 \&.Op \&Fl a \&Ar b
.D1 \&.Op \&Ar a | b
.Pp
See also
.Sx \&Oo .
.Ss \&Os
Document operating system version.
This is the mandatory third macro of
any
.Nm
file.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Os Op Cm system
.Pp
The optional
.Cm system
parameter specifies the relevant operating system or environment.
Left unspecified, it defaults to the local operating system version.
This is the suggested form.
.Pp
Examples:
.D1 \&.Os
.D1 \&.Os KTH/CSC/TCS
.D1 \&.Os BSD 4.3
.Pp
See also
.Sx \&Dd
and
.Sx \&Dt .
.Ss \&Ot
Unknown usage.
.Pp
.Em Remarks :
this macro has been deprecated.
.Ss \&Ox
Format the OpenBSD version provided as an argument, or a default value
if no argument is provided.
.Pp
Examples:
.D1 \&.Ox 4.5
.D1 \&.Ox
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
and
.Sx \&Ux .
.Ss \&Pa
A file-system path.
.Pp
Examples:
.D1 \&.Pa /usr/bin/mandoc
.D1 \&.Pa /usr/share/man/man7/mdoc.7
.Pp
See also
.Sx \&Lk .
.Ss \&Pc
Close parenthesised context opened by
.Sx \&Po .
.Ss \&Pf
Removes the space
.Pq Dq prefix
between its arguments.
Its syntax is as follows:
.Pp
.D1 Pf \. \&Pf Cm prefix suffix
.Pp
The
.Cm suffix
argument may be a macro.
.Pp
Examples:
.D1 \&.Pf \e. \&Sx \&Pf \&Cm prefix suffix
.Ss \&Po
Multi-line version of
.Sx \&Pq .
.Ss \&Pp
Break a paragraph.
This will assert vertical space between prior and subsequent macros
and/or text.
.Ss \&Pq
Parenthesised enclosure.
.Pp
See also
.Sx \&Po .
.Ss \&Qc
Close quoted context opened by
.Sx \&Qo .
.Ss \&Ql
Format a single-quoted literal.
See also
.Sx \&Qq
and
.Sx \&Sq .
.Ss \&Qo
Multi-line version of
.Sx \&Qq .
.Ss \&Qq
Encloses its arguments in
.Dq typewriter
double-quotes.
Consider using
.Sx \&Dq .
.Pp
See also
.Sx \&Dq ,
.Sx \&Sq ,
and
.Sx \&Qo .
.Ss \&Re
Close an
.Sx \&Rs
block.
Does not have any tail arguments.
.Ss \&Rs
Begin a bibliographic
.Pq Dq reference
block.
Does not have any head arguments.
The block macro may only contain
.Sx \&%A ,
.Sx \&%B ,
.Sx \&%C ,
.Sx \&%D ,
.Sx \&%I ,
.Sx \&%J ,
.Sx \&%N ,
.Sx \&%O ,
.Sx \&%P ,
.Sx \&%Q ,
.Sx \&%R ,
.Sx \&%T ,
.Sx \&%U ,
and
.Sx \&%V
child macros (at least one must be specified).
.Pp
Examples:
.Bd -literal -offset indent -compact
\&.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
.Ed
.Pp
If an
.Sx \&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.
.Ss \&Rv
Inserts text regarding a function call's return value.
This macro must consist of the
.Fl std
argument followed by an optional
.Ar function .
If
.Ar function
is not provided, the document's name as stipulated by the first
.Sx \&Nm
is provided.
.Pp
See also
.Sx \&Ex .
.Ss \&Sc
Close single-quoted context opened by
.Sx \&So .
.Ss \&Sh
Begin a new section.
For a list of conventional manual sections, see
.Sx MANUAL STRUCTURE .
These sections should be used unless it's absolutely necessary that
custom sections be used.
.Pp
Section names should be unique so that they may be keyed by
.Sx \&Sx .
.Pp
See also
.Sx \&Pp ,
.Sx \&Ss ,
and
.Sx \&Sx .
.Ss \&Sm
Switches the spacing mode for output generated from macros.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Sm Cm on | off
.Pp
By default, spacing is
.Cm on .
When switched
.Cm off ,
no white space is inserted between macro arguments and between the
output generated from adjacent macros, but free-form text lines
still get normal spacing between words and sentences.
.Ss \&So
Multi-line version of
.Sx \&Sq .
.Ss \&Sq
Encloses its arguments in
.Dq typewriter
single-quotes.
.Pp
See also
.Sx \&Dq ,
.Sx \&Qq ,
and
.Sx \&So .
.Ss \&Ss
Begin a new sub-section.
Unlike with
.Sx \&Sh ,
there's no convention for sub-sections.
Conventional sections, as described in
.Sx MANUAL STRUCTURE ,
rarely have sub-sections.
.Pp
Sub-section names should be unique so that they may be keyed by
.Sx \&Sx .
.Pp
See also
.Sx \&Pp ,
.Sx \&Sh ,
and
.Sx \&Sx .
.Ss \&St
Replace an abbreviation for a standard with the full form.
The following standards are recognised:
.Pp
.Bl -tag -width "-p1003.1g-2000X" -compact
.It \-p1003.1-88
.St -p1003.1-88
.It \-p1003.1-90
.St -p1003.1-90
.It \-p1003.1-96
.St -p1003.1-96
.It \-p1003.1-2001
.St -p1003.1-2001
.It \-p1003.1-2004
.St -p1003.1-2004
.It \-p1003.1-2008
.St -p1003.1-2008
.It \-p1003.1
.St -p1003.1
.It \-p1003.1b
.St -p1003.1b
.It \-p1003.1b-93
.St -p1003.1b-93
.It \-p1003.1c-95
.St -p1003.1c-95
.It \-p1003.1g-2000
.St -p1003.1g-2000
.It \-p1003.1i-95
.St -p1003.1i-95
.It \-p1003.2-92
.St -p1003.2-92
.It \-p1003.2a-92
.St -p1003.2a-92
.It \-p1387.2-95
.St -p1387.2-95
.It \-p1003.2
.St -p1003.2
.It \-p1387.2
.St -p1387.2
.It \-isoC
.St -isoC
.It \-isoC-90
.St -isoC-90
.It \-isoC-amd1
.St -isoC-amd1
.It \-isoC-tcor1
.St -isoC-tcor1
.It \-isoC-tcor2
.St -isoC-tcor2
.It \-isoC-99
.St -isoC-99
.It \-iso9945-1-90
.St -iso9945-1-90
.It \-iso9945-1-96
.St -iso9945-1-96
.It \-iso9945-2-93
.St -iso9945-2-93
.It \-ansiC
.St -ansiC
.It \-ansiC-89
.St -ansiC-89
.It \-ansiC-99
.St -ansiC-99
.It \-ieee754
.St -ieee754
.It \-iso8802-3
.St -iso8802-3
.It \-ieee1275-94
.St -ieee1275-94
.It \-xpg3
.St -xpg3
.It \-xpg4
.St -xpg4
.It \-xpg4.2
.St -xpg4.2
.St -xpg4.3
.It \-xbd5
.St -xbd5
.It \-xcu5
.St -xcu5
.It \-xsh5
.St -xsh5
.It \-xns5
.St -xns5
.It \-xns5.2
.St -xns5.2
.It \-xns5.2d2.0
.St -xns5.2d2.0
.It \-xcurses4.2
.St -xcurses4.2
.It \-susv2
.St -susv2
.It \-susv3
.St -susv3
.It \-svid4
.St -svid4
.El
.Ss \&Sx
Reference a section or sub-section.
The referenced section or sub-section name must be identical to the
enclosed argument, including whitespace.
.Pp
Examples:
.D1 \&.Sx MANUAL STRUCTURE
.Ss \&Sy
Format enclosed arguments in symbolic
.Pq Dq boldface .
Note that this is a presentation term and should not be used for
stylistically decorating technical terms.
.Pp
See also
.Sx \&Bf ,
.Sx \&Li ,
and
.Sx \&Em .
.Ss \&Tn
Format a tradename.
.Pp
Examples:
.D1 \&.Tn IBM
.Ss \&Ud
Prints out
.Dq currently under development.
.Ss \&Ux
Format the UNIX name.
Accepts no argument.
.Pp
Examples:
.D1 \&.Ux
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
and
.Sx \&Ox .
.Ss \&Va
A variable name.
.Pp
Examples:
.D1 \&.Va foo
.D1 \&.Va const char *bar ;
.Ss \&Vt
A variable type.
This is also used for indicating global variables in the
.Em SYNOPSIS
section, in which case a variable name is also specified.
Note that it accepts
.Sx Block partial-implicit
syntax when invoked as the first macro in the
.Em SYNOPSIS
section, else it accepts ordinary
.Sx In-line
syntax.
.Pp
Note that this should not be confused with
.Sx \&Ft ,
which is used for function return types.
.Pp
Examples:
.D1 \&.Vt unsigned char
.D1 \&.Vt extern const char * const sys_signame[] \&;
.Pp
See also
.Sx MANUAL STRUCTURE
and
.Sx \&Va .
.Ss \&Xc
Close a scope opened by
.Sx \&Xo .
.Ss \&Xo
Open an extension scope.
This macro originally existed to extend the 9-argument limit of troff;
since this limit has been lifted, the macro has been deprecated.
.Ss \&Xr
Link to another manual
.Pq Qq cross-reference .
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&Xr Cm name section
.Pp
The
.Cm name
and
.Cm section
are the name and section of the linked manual.
If
.Cm section
is followed by non-punctuation, an
.Sx \&Ns
is inserted into the token stream.
This behaviour is for compatibility with
.Xr groff 1 .
.Pp
Examples:
.D1 \&.Xr mandoc 1
.D1 \&.Xr mandoc 1 \&;
.D1 \&.Xr mandoc 1 \&Ns s behaviour
.Ss \&br
Emits a line-break.
This macro should not be used; it is implemented for compatibility with
historical manuals.
.Pp
Consider using
.Sx \&Pp
in the event of natural paragraph breaks.
.Ss \&sp
Emits vertical space.
This macro should not be used; it is implemented for compatibility with
historical manuals.
Its syntax is as follows:
.Pp
.D1 Pf \. Sx \&sp Op Cm height
.Pp
The
.Cm height
argument must be formatted as described in
.Sx Scaling Widths .
If unspecified,
.Sx \&sp
asserts a single vertical space.
.Sh COMPATIBILITY
This section documents compatibility between mandoc and other other
troff implementations, at this time limited to GNU troff
.Pq Qq groff .
The term
.Qq historic groff
refers to groff versions before the
.Pa doc.tmac
file re-write
.Pq somewhere between 1.15 and 1.19 .
.Pp
Heirloom troff, the other significant troff implementation accepting
\-mdoc, is similar to historic groff.
.Pp
.Bl -dash -compact
.It
An empty
.Sq \&Dd
macro in groff prints
.Dq Epoch .
In mandoc, it resolves to the current date.
.It
The \es (font size), \em (font colour), and \eM (font filling colour)
font decoration escapes are all discarded in mandoc.
.It
Old groff fails to assert a newline before
.Sx \&Bd Fl ragged compact .
.It
groff behaves inconsistently when encountering
.Pf non- Sx \&Fa
children of
.Sx \&Fo
regarding spacing between arguments.
In mandoc, this is not the case: each argument is consistently followed
by a single space and the trailing
.Sq \&)
suppresses prior spacing.
.It
groff behaves inconsistently when encountering
.Sx \&Ft
and
.Sx \&Fn
in the
.Em SYNOPSIS :
at times newline(s) are suppressed depending on whether a prior
.Sx \&Fn
has been invoked.
In mandoc, this is not the case.
See
.Sx \&Ft
and
.Sx \&Fn
for the normalised behaviour.
.It
Historic groff does not break before an
.Sx \&Fn
when not invoked as the line macro in the
.Em SYNOPSIS
section.
.It
Historic groff formats the
.Sx \&In
badly: trailing arguments are trashed and
.Em SYNOPSIS
is not specially treated.
.It
groff does not accept the
.Sq \&Ta
pseudo-macro as a line macro.
mandoc does.
.It
The comment syntax
.Sq \e\."
is no longer accepted.
.It
In groff, the
.Sx \&Pa
macro does not format its arguments when used in the FILES section under
certain list types.
mandoc does.
.It
Historic groff does not print a dash for empty
.Sx \&Fl
arguments.
mandoc and newer groff implementations do.
.It
groff behaves irregularly when specifying
.Sq \ef
.Sx Text Decoration
within line-macro scopes.
mandoc follows a consistent system.
.It
In mandoc, negative scaling units are truncated to zero; groff would
move to prior lines.
Furthermore, the
.Sq f
scaling unit, while accepted, is rendered as the default unit.
.It
In quoted literals, groff allowed pair-wise double-quotes to produce a
standalone double-quote in formatted output.
This idiosyncratic behaviour is not applicable in mandoc.
.It
Display offsets
.Sx \&Bd
.Fl offset Ar center
and
.Fl offset Ar right
are disregarded in mandoc.
Furthermore, troff specifies a
.Fl file Ar file
argument that is not supported in mandoc.
Lastly, since text is not right-justified in mandoc (or even groff),
.Fl ragged
and
.Fl filled
are aliases, as are
.Fl literal
and
.Fl unfilled .
.It
Historic groff has many un-callable macros.
Most of these (excluding some block-level macros) are now callable.
.It
The vertical bar
.Sq \(ba
made historic groff
.Qq go orbital
but has been a proper delimiter since then.
.It
.Sx \&It Fl nested
is assumed for all lists (it wasn't in historic groff): any list may be
nested and
.Fl enum
lists will restart the sequence only for the sub-list.
.It
Some manuals use
.Sx \&Li
incorrectly by following it with a reserved character and expecting the
delimiter to render.
This is not supported in mandoc.
.It
In groff, the
.Sx \&Cd ,
.Sx \&Er ,
.Sx \&Ex ,
and
.Sx \&Rv
macros were stipulated only to occur in certain manual sections.
mandoc does not have these restrictions.
.It
Newer groff and mandoc print
.Qq AT&T UNIX
prior to unknown arguments of
.Sx \&At ;
older groff did nothing.
.El
.Sh SEE ALSO
.Xr mandoc 1 ,
.Xr mandoc_char 7
.Sh AUTHORS
The
.Nm
reference was written by
.An Kristaps Dzonsons Aq kristaps@bsd.lv .