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.\"     $Id: mdoc.7,v 1.75 2009/11/06 10:31:31 kristaps Exp $
.\"
.\" Copyright (c) 2009 Kristaps Dzonsons <kristaps@kth.se>
.\"
.\" 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
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: November 6 2009 $
.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
.Xr mandoc 1 .
The
.Sx COMPATIBILITY
section describes compatibility with
.Xr groff 1 .
.
.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" ,
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" ,
is also ignored.  Macro lines with only a control charater 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 must either be escaped
with a non-breaking space
.Pq Sq \e&
or, if applicable, an appropriate escape sequence 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).  A numerical representation 3, 2, or 1
(bold, italic, and Roman, respectively) may be used instead.  
.Pp
These form is 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 ,
demark 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
In non-literal free-form lines, consecutive blocks of whitespace are
pruned from input and added later in the output filter, if applicable:
.Bd -literal -offset indent
These     spaces   are    pruned       from    input.
\&.Bd \-literal
These         are              not.
\&.Ed
.Ed
.
.Pp
In macro lines, whitespace delimits arguments and is discarded.  If
arguments are quoted, whitespace within the quotes is retained.
.
.Pp
Blank lines are only permitted within literal contexts, as are lines
containing only whitespace.  Tab characters are only acceptable when
delimiting
.Sq \&Bl \-column
or when in a literal context.
.
.
.Ss Quotation
Macro arguments may be quoted with a double-quote 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
This produces tokens
.Sq a" ,
.Sq b c ,
.Sq de ,
and
.Sq fg" .
Note that any quoted term, be it argument or macro, is indiscriminately
considered literal text.  Thus, the following produces
.Sq \&Em a :
.Bd -literal -offset indent
\&.Em "Em 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 .
.
.
.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 (in order) the
.Sx \&Dd ,
.Sx \&Dt ,
and
.Sx \&Os
macros, 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 SYNOPSIS and
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 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 1 & 8 only.
\&.\e\*q .Sh EXIT STATUS
\&.\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 .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 short description of the documented material.  The
syntax for this as follows:
.Bd -literal -offset indent
\&.Nm name0
\&.Nm name1
\&.Nm name2
\&.Nd a short description
.Ed
.Pp
The
.Sx \&Nm
macro(s) must precede the
.Sx \&Nd
macro.
.
.It Em LIBRARY
The name of the library containing the documented material, which is
assumed to be a function in a section 2 or 3 manual.  The syntax for
this is as follows:
.Bd -literal -offset indent
\&.Lb libarm
.Ed
.Pp
See
.Sx \&Lb
for details.
.
.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 .
.
.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
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 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 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
Documents any usages of environment variables, e.g.,
.Xr environ 7 .
.Pp
See
.Sx \&Ev .
.
.It Em FILES
Documents files used.  It's helpful to document both the file and a
short description of how the file is used (created, modified, etc.).
.Pp
See
.Sx \&Pa .
.
.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 No \-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 an e-mail address.
.Pp
See
.Sx \&An .
.
.It Em CAVEATS
Explanations of common misuses and misunderstandings should be explained
in this section.
.
.It Em BUGS
Extant bugs 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 Parsable
column indicates whether the macro may be followed by further
(ostensibly callable) macros.  If a macro is not parsable, 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" "ParsableX" "closed by XXX"
.It Em Macro Ta Em Callable Ta Em Parsable 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 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" "ParsableX" "closed by XXXXXXXXXXX"
.It Em Macro Ta Em Callable Ta Em Parsable 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 \&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
.
.
.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" "ParsableX" "closed by XXXX" -compact -offset indent
.It Em Macro Ta Em Callable Ta Em Parsable 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" "ParsableX" -compact -offset indent
.It Em Macro Ta Em Callable Ta Em Parsable
.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
.El
.
.
.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" "ParsableX" "Arguments" -compact -offset indent
.It Em Macro Ta Em Callable Ta Em Parsable 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    >0
.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    \&No     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, <3
.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
Closes an
.Sx \&Ao
block.  Does not have any tail arguments.
.
.Ss \&Ad
Address construct: usually in the context of an computational address in
memory, not a physical (post) address.
.Pp
Examples:
.Bd -literal -offset indent
\&.Ad [0,$]
\&.Ad 0x00000000
.Ed
.
.Ss \&An
Author name.  This macro may alternatively accepts the following
arguments, although these may not be specified along with a parameter:
.Bl -tag -width 12n -offset indent
.It Fl split
Renders a line break before each author listing.
.It Fl nosplit
The opposite of
.Fl split .
.El
.Pp
In the AUTHORS section, the default is not to split the first author
listing, but all subsequent author listings, whether or not they're
interspersed by other macros or text, are split.  Thus, specifying
.Fl split
will cause the first listing also to be split.  If not in the AUTHORS
section, the default is not to split.
.Pp
Examples:
.Bd -literal -offset indent
\&.An -nosplit
\&.An J. E. Hopcraft ,
\&.An J. D. Ullman .
.Ed
.Pp
.Em Remarks :
the effects of
.Fl split
or
.Fl nosplit
are re-set when entering the AUTHORS section, so if one specifies
.Sx \&An Fl nosplit
in the general document body, it must be re-specified in the AUTHORS
section.
.
.Ss \&Ao
Begins a block enclosed by angled brackets.  Does not have any head
arguments.
.Pp
Examples:
.Bd -literal -offset indent
\&.Fl -key= Ns Ao Ar val Ac
.Ed
.Pp
See also
.Sx \&Aq .
.
.Ss \&Ap
Inserts an apostrophe without any surrounding white-space.  This is
generally used as a grammatic device when referring to the verb form of
a function:
.Bd -literal -offset indent
\&.Fn execve Ap d
.Ed
.
.Ss \&Aq
Encloses its arguments in angled brackets.  
.Pp
Examples:
.Bd -literal -offset indent
\&.Fl -key= Ns Aq Ar val
.Ed
.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:
.Bd -literal -offset indent
\&.Fl o Ns Ar file1
\&.Ar
\&.Ar arg1 , arg2 .
.Ed
.
.Ss \&At
Formats an AT&T version.  Accepts at most one parameter:
.Bl -tag -width 12n -offset indent
.It Cm v[1-7] | 32v
A version of
.At .
.It Cm V[.[1-4]]?
A system version of
.At .
.El
.Pp
Note that these parameters do not begin with a hyphen.
.Pp
Examples:
.Bd -literal -offset indent
\&.At 
\&.At V.1
.Ed
.Pp
See also
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.
.Ss \&Bc
Closes a
.Sx \&Bo
block.  Does not have any tail arguments.
.
.Ss \&Bd
Begins a display block.  A display is collection of macros or text which
may be collectively offset or justified in a manner different from that
of the enclosing context.  By default, the block is preceded by a
vertical space.
.Pp
Each display is associated with a type, which must be one of the
following arguments:
.Bl -tag -width 12n -offset indent
.It Fl ragged
Only left-justify the block.
.It Fl unfilled
Do not justify the block at all.
.It Fl filled
Left- and right-justify the block.
.It Fl literal
Alias for
.Fl unfilled .
.It Fl centered
Centre-justify each line.
.El
.Pp
The type must be provided first.  Secondary arguments are as follows:
.Bl -tag -width 12n -offset indent
.It Fl offset Ar width
Offset by the value of
.Ar width ,
which is interpreted as one of the following, specified in order:
.Bl -item
.It
As one of the pre-defined strings
.Ar indent ,
the width of standard indentation;
.Ar indent-two ,
twice
.Ar indent ;
.Ar left ,
which has no effect ;
.Ar right ,
which justifies to the right margin; and
.Ar center ,
which aligns around an imagined centre axis.
.It
As a precalculated width for a named macro.  The most popular is the
imaginary macro
.Ar \&Ds ,
which resolves to
.Ar 6n .
.It
As a scaling unit following the syntax described in
.Sx Scaling Widths .
.It
As the calculated string length of the opaque string.
.El
.Pp
If unset, it will revert to the value of
.Ar 8n
as described in
.Sx Scaling Widths .
.It Fl compact
Do not assert a vertical space before the block.
.It Fl file Ar file
Prepend the file
.Ar file
before any text or macros within the block.
.El
.Pp
Examples:
.Bd -literal -offset indent
\&.Bd \-unfilled \-offset two-indent \-compact
   Hello       world.
\&.Ed
.Ed
.Pp
See also
.Sx \&D1
and
.Sx \&Dl .
.
.Ss \&Bf
.Ss \&Bk
.Ss \&Bl
.
.Ss \&Bo
Begins a block enclosed by square brackets.  Does not have any head
arguments.
.Pp
Examples:
.Bd -literal -offset indent
\&.Bo 1 ,
\&.Dv BUFSIZ Bc
.Ed
.Pp
See also
.Sx \&Bq .
.
.Ss \&Bq
Encloses its arguments in square brackets.  
.Pp
Examples:
.Bd -literal -offset indent
\&.Bq 1 , Dv BUFSIZ
.Ed
.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
Closes a
.Sx \&Bro
block.  Does not have any tail arguments.
.
.Ss \&Bro
Begins a block enclosed by curly braces.  Does not have any head
arguments.
.Pp
Examples:
.Bd -literal -offset indent
\&.Bro 1 , ... ,
\&.Va n Brc
.Ed
.Pp
See also
.Sx \&Brq .
.
.Ss \&Brq
Encloses its arguments in curly braces.
.Pp
Examples:
.Bd -literal -offset indent
\&.Brq 1 , ... , Va n
.Ed
.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:
.Bd -literal -offset indent
\&.Bsx 1.0
\&.Bsx
.Ed
.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:
.Bd -literal -offset indent
\&.Bx 4.4
\&.Bx
.Ed
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.
.Ss \&Cd
Configuration declaration (suggested for use only in section four
manuals).  This denotes strings accepted by
.Xr config 8 .
.Pp
Examples:
.Bd -literal -offset indent
\&.Cd device le0 at scode?
.Ed
.Pp
.Em Remarks :
this macro is commonly abused by using quoted literals to retain
white-space and align consecutive
.Sx \&Cd
declarations.  This practise is discouraged.
.
.Ss \&Cm
Command modifiers.  Useful when specifying configuration options or
keys.
.Pp
Examples:
.Bd -literal -offset indent
\&.Cm ControlPath
\&.Cm ControlMaster
.Ed
.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:
.Bd -literal -offset indent
\&.D1 Fl abcdefgh
.Ed
.Pp
See also
.Sx \&Bd
and
.Sx \&Dl .
.
.Ss \&Db
.Ss \&Dc
Closes 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 calling syntax is as follows:
.Pp
.D1 \. Ns Sx \&Dd Cm date
.Pp
The 
.Cm date
field 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, the current date is used instead.
.Pp
Examples:
.Bd -literal -offset indent
\&.Dd $\&Mdocdate$
\&.Dd $\&Mdocdate: July 21 2007$
\&.Dd July 21, 2007
.Ed
.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:
.Bd -literal -offset indent
\&.Dl % mandoc mdoc.7 | less
.Ed
.Pp
See also
.Sx \&Bd
and
.Sx \&D1 .
.
.Ss \&Do
Begins a block enclosed by double quotes.  Does not have any head
arguments.
.Pp
Examples:
.Bd -literal -offset indent
\&.D1 Do April is the cruellest month Dc \e(em T.S. Eliot
.Ed
.Pp
See also
.Sx \&Dq .
.
.Ss \&Dq
Encloses its arguments in double quotes.  
.Pp
Examples:
.Bd -literal -offset indent
\&.Dq April is the cruellest month
\e(em T.S. Eliot
.Ed
.Pp
See also
.Sx \&Do .
.
.Ss \&Dt
Document title.  This is the mandatory second macro of any
.Nm
file.  Its calling syntax is as follows:
.Pp
.D1 \. Ns Sx \&Dt Cm title section Op Cm volume | arch
.Pp
Its arguments are as follows:
.Bl -tag -width Ds -offset Ds
.It Cm title
The document's title (name).  This should be capitalised and is
required.
.It Cm 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 is also required and should correspond to the manual's filename
suffix.
.It Cm 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 Cm arch
This specifies a specific relevant architecture.  If
.Cm 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 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:
.Bd -literal -offset indent
\&.Dt FOO 1
\&.Dt FOO 4 KM
\&.Dt FOO 9 i386
\&.Dt FOO 9 KM i386
.Ed
.Pp
See also
.Sx \&Dd
and
.Sx \&Os .
.
.Ss \&Dv
Defined variables such as preprocessor constants.
.Pp
Examples:
.Bd -literal -offset indent
\&.Dv BUFSIZ
\&.Dv STDOUT_FILENO
.Ed
.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:
.Bd -literal -offset indent
\&.Dx 2.4.1
\&.Dx
.Ed
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Fx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.
.Ss \&Ec
.Ss \&Ed
.Ss \&Ef
.Ss \&Ek
.Ss \&El
.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:
.Bd -literal -offset indent
\&.Ed Warnings!
\&.Ed Remarks :
.Ed
.
.Ss \&En
.Ss \&Eo
.Ss \&Er
Error constants (suggested for use only in section two manuals).
.Pp
Examples:
.Bd -literal -offset indent
\&.Er EPERM
\&.Er ENOENT
.Ed
.Pp
See also
.Sx \&Dv .
.
.Ss \&Es
.
.Ss \&Ev
Environmental variables such as those specified in
.Xr environ 7 .
.Pp
Examples:
.Bd -literal -offset indent
\&.Ev DISPLAY
\&.Ev PATH
.Ed
.
.Ss \&Ex
Inserts text regarding a utility's exit values.  This macro must have
first the
.Fl std
argument specified, then an optional
.Ar utility .
If
.Ar utility
is not provided, the document's name as stipulated in
.Sx \&Nm
is provided.
.Ss \&Fa
.Ss \&Fc
.Ss \&Fd
.Ss \&Fl
.Ss \&Fn
.Ss \&Fo
.Ss \&Fr
.Ss \&Ft
.Ss \&Fx
Format the FreeBSD version provided as an argument, or a default value
if no argument is provided.
.Pp
Examples:
.Bd -literal -offset indent
\&.Fx 7.1
\&.Fx
.Ed
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Nx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.
.Ss \&Hf
.Ss \&Ic
.Ss \&In
.Ss \&It
.Ss \&Lb
.Ss \&Li
.Ss \&Lk
Format a hyperlink.  The calling syntax is as follows:
.Pp
.D1 \. Ns Sx \&Lk Cm uri Op Cm name
.Pp
Examples:
.Bd -literal -offset indent
\&.Lk http://bsd.lv "The BSD.lv Project"
\&.Lk http://bsd.lv
.Ed
.Pp
See also
.Sx \&Mt .
.
.Ss \&Lp
.Ss \&Ms
.Ss \&Mt
.Ss \&Nd
.Ss \&Nm
.Ss \&No
.Ss \&Ns
.Ss \&Nx
Format the NetBSD version provided as an argument, or a default value if
no argument is provided.
.Pp
Examples:
.Bd -literal -offset indent
\&.Nx 5.01
\&.Nx
.Ed
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Ox ,
and
.Sx \&Ux .
.
.Ss \&Oc
.Ss \&Oo
.Ss \&Op
.Ss \&Os
Document operating system version.  This is the mandatory third macro of
any
.Nm
file.  Its calling syntax is as follows:
.Pp
.D1 \. Ns 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:
.Bd -literal -offset indent
\&.Os
\&.Os KTH/CSC/TCS
\&.Os BSD 4.3
.Ed
.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:
.Bd -literal -offset indent
\&.Ox 4.5
\&.Ox
.Ed
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
and
.Sx \&Ux .
.
.Ss \&Pa
.Ss \&Pc
.Ss \&Pf
.Ss \&Po
.Ss \&Pp
.Ss \&Pq
.Ss \&Qc
.Ss \&Ql
.Ss \&Qo
.Ss \&Qq
.
.Ss \&Re
Closes a
.Sx \&Rs
block.  Does not have any tail arguments.
.
.Ss \&Rs
Begins 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 ,
and
.Sx \&%V
child macros (at least one must be specified).
.Pp
Examples:
.Bd -literal -offset indent
\&.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
.Ss \&Sc
.Ss \&Sh
.Ss \&Sm
.Ss \&So
.Ss \&Sq
.Ss \&Ss
.Ss \&St
.Ss \&Sx
.Ss \&Sy
.Ss \&Tn
.Ss \&Ud
.Ss \&Ux
Format the UNIX name.  Accepts no argument.
.Pp
Examples:
.Bd -literal -offset indent
\&.Ux
.Ed
.Pp
See also
.Sx \&At ,
.Sx \&Bsx ,
.Sx \&Bx ,
.Sx \&Dx ,
.Sx \&Fx ,
.Sx \&Nx ,
and
.Sx \&Ox .
.
.Ss \&Va
.Ss \&Vt
.Ss \&Xc
.Ss \&Xo
.Ss \&Xr
.Ss \&br
.Ss \&sp
.
.
.Sh COMPATIBILITY
This section documents compatibility with other roff implementations, at
this time limited to
.Xr groff 1 .
The term
.Qq historic groff
refers to those versions before the
.Pa doc.tmac
file re-write
.Pq somewhere between 1.15 and 1.19 .
.
.Pp
.Bl -dash -compact
.It
Negative scaling units are now truncated to zero instead of creating
interesting conditions, such as with
.Sq \&sp -1i .
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 no longer applicable.
.It
Display types
.Sx \&Bd Fl center
and
.Fl right
are aliases for
.Fl left .
The
.Fl file Ar file
argument is ignored.  Since text is not right-justified,
.Fl ragged
and
.Fl filled
are aliases, as are
.Fl literal
and
.Fl unfilled .
.It
Blocks of whitespace are stripped from both macro and free-form text
lines (except when in literal mode), while groff would retain whitespace
in free-form text lines.
.It
Historic groff has many un-callable macros.  Most of these (excluding
some block-level macros) are now callable, conforming to the
non-historic groff version.
.It
The vertical bar
.Sq \(ba
made historic groff
.Qq go orbital
but is a proper delimiter in this implementation.
.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.
.It
In groff, the
.Sx \&Fo
macro only produces the first parameter.  This is no longer the case.
.El
.
.
.Sh SEE ALSO
.Xr mandoc 1 ,
.Xr mandoc_char 7
.
.
.Sh AUTHORS
The
.Nm
reference was written by
.An Kristaps Dzonsons Aq kristaps@kth.se .
.\"
.\" XXX: this really isn't the place for these caveats.
.\" .
.\" .
.\" .Sh CAVEATS
.\" There are many ambiguous parts of mdoc.
.\" .
.\" .Pp
.\" .Bl -dash -compact
.\" .It
.\" .Sq \&Fa
.\" should be
.\" .Sq \&Va
.\" as function arguments are variables.
.\" .It
.\" .Sq \&Ft
.\" should be
.\" .Sq \&Vt
.\" as function return types are still types.  Furthermore, the
.\" .Sq \&Ft
.\" should be removed and
.\" .Sq \&Fo ,
.\" which ostensibly follows it, should follow the same convention as
.\" .Sq \&Va .
.\" .It
.\" .Sq \&Va
.\" should formalise that only one or two arguments are acceptable: a
.\" variable name and optional, preceding type.
.\" .It
.\" .Sq \&Fd
.\" is ambiguous.  It's commonly used to indicate an include file in the
.\" synopsis section.
.\" .Sq \&In
.\" should be used, instead.
.\" .It
.\" Only the
.\" .Sq \-literal
.\" argument to
.\" .Sq \&Bd
.\" makes sense.  The remaining ones should be removed.
.\" .It
.\" The
.\" .Sq \&Xo
.\" and
.\" .Sq \&Xc
.\" macros should be deprecated.
.\" .It
.\" The
.\" .Sq \&Dt
.\" macro lacks clarity.  It should be absolutely clear which title will
.\" render when formatting the manual page.
.\" .It
.\" A
.\" .Sq \&Lx
.\" should be provided for Linux (\(`a la
.\" .Sq \&Ox ,
.\" .Sq \&Nx
.\" etc.).
.\" .It
.\" There's no way to refer to references in
.\" .Sq \&Rs/Re
.\" blocks.
.\" .It
.\" The \-split and \-nosplit dictates via
.\" .Sq \&An
.\" are re-set when entering and leaving the AUTHORS section.
.\" .El
.\" .