Fix issue of non-NAME sections triggering "no sections" error, reported by Christian...

[mandoc.git] / man.7

.\"     $Id: man.7,v 1.61 2010/04/05 07:25:23 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
.\" 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: April 5 2010 $
.Dt MAN 7
.Os
.
.
.Sh NAME
.Nm man
.Nd man language reference
.
.
.Sh DESCRIPTION
The
.Nm man
language was historically used to format
.Ux
manuals.  This reference document describes its syntax, structure, and
usage.
.
.Pp
.Bf -emphasis
Do not use
.Nm
to write your manuals.
.Ef
Use the
.Xr mdoc 7
language, instead.
.
.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 INPUT ENCODING
.Nm
documents may contain only graphable 7-bit ASCII characters, the
space character, and the tabs character.  All manuals must have
.Ux
line termination.
.
.Pp
Blank lines are acceptable; where found, the output will assert a
vertical space.
.
.
.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 character and
optionally whitespace are stripped from input.
.
.
.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 only valid, if
specified in free-form text, until the next macro invocation; if
specified within a macro, it's only valid until the macro closes scope.
Note that macros like
.Sx \&BR
open and close a font scope with each argument.
.Pp
Text may also be sized with the
.Sq \es
escape, whose syntax is one of
.Sq \es+-n
for one-digit numerals;
.Sq \es(+-nn
or
.Sq \es+-(nn
for two-digit numerals; and
.Sq \es[+-N] ,
.Sq \es+-[N] ,
.Sq \es'+-N' ,
or
.Sq \es+-'N'
for arbitrary-digit numerals:
.Pp
.D1 \es+1bigger\es-1
.D1 \es[+10]much bigger\es[-10]
.D1 \es+(10much bigger\es-(10
.D1 \es+'100'much much bigger\es-'100'
.Pp
Both
.Sq \es
and
.Sq \ef
attributes are forgotten when entering or exiting a macro block.
.
.
.Ss Whitespace
Unless specifically escaped, consecutive blocks of whitespace are pruned
from input.  These are later re-added, if applicable, by a front-end
utility such as
.Xr mandoc 1 .
.
.
.Ss Dates
The
.Sx \&TH
macro is the only
.Nm
macro that requires a date.  The form for this date is the ISO-8601
standard
.Cm YYYY-MM-DD .
.
.
.Ss Scaling Widths
Many macros support scaled widths for their arguments, such as
stipulating a two-inch paragraph indentation with the following:
.Bd -literal -offset indent
\&.HP 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.
.
.Pp
If a scaling unit is not provided, the numerical value is interpreted
under the default rules of
.Sq v
for vertical spaces and
.Sq u
for horizontal ones.
.Em Note :
this differs from
.Xr mdoc 7 ,
which, if a unit is not provided, will instead interpret the string as
literal text.
.
.
.Sh MANUAL STRUCTURE
Each
.Nm
document must contain contains at least the
.Sx \&TH
macro describing the document's section and title.  It may occur
anywhere in the document, although conventionally, it appears as the
first macro.
.
.Pp
Beyond
.Sx \&TH ,
at least one macro or text node must appear in the document.  Documents
are generally structured as follows:
.Bd -literal -offset indent
\&.TH FOO 1 2009-10-10
\&.
\&.SH NAME
\efBfoo\efR \e(en a description goes here
\&.\e\*q The next is for sections 2 & 3 only.
\&.\e\*q .SH LIBRARY
\&.
\&.SH SYNOPSIS
\efBfoo\efR [\efB\e-options\efR] arguments...
\&.
\&.SH DESCRIPTION
The \efBfoo\efR 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 .BR foo ( 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 indent
.It Em NAME
The name(s) and a short description of the documented material.  The
syntax for this is generally as follows:
.Pp
.D1 \efBname\efR \e(en description
.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.  For functions in
the C library, this may be as follows:
.Pp
.D1 Standard C Library (libc, -lc)
.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:
.Pp
.D1 \efBname\efR [-\efBab\efR] [-\efBc\efR\efIarg\efR] \efBpath\efR...
.Pp
For the second, function calls (sections 2, 3, 9):
.Pp
.D1 \&.B char *name(char *\efIarg\efR);
.Pp
And for the third, configurations (section 4):
.Pp
.D1 \&.B name* at cardbus ? function ?
.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).
.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.
.
.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.
.
.It Em ENVIRONMENT
Documents any usages of environment variables, e.g.,
.Xr environ 7 .
.
.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.).
.
.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.
.
.It Em ERRORS
Documents error handling in sections 2, 3, and 9.
.
.It Em SEE ALSO
References other manuals with related topics.  This section should exist
for most manuals.
.Pp
.D1 \&.BR bar \&( 1 \&),
.Pp
Cross-references should conventionally be ordered
first by section, then alphabetically.
.
.It Em STANDARDS
References any standards implemented or used, such as
.Pp
.D1 IEEE Std 1003.2 (\e(lqPOSIX.2\e(rq)
.Pp
If not adhering to any standards, the
.Em HISTORY
section should be used.
.
.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.
.
.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.  The
.Sq \(aq
macro control character is also accepted.  An arbitrary amount of
whitespace (spaces or tabs) may sit between the control character and
the macro name.  Thus, the following are equivalent:
.Bd -literal -offset indent
\&.PP
\&.\ \ \ PP
.Ed
.
.Pp
The
.Nm
macros are classified by scope: line scope or block scope.  Line
macros are only scoped to the current line (and, in some situations,
the subsequent line).  Block macros are scoped to the current line and
subsequent lines until closed by another block macro.
.
.
.Ss Line Macros
Line macros are generally scoped to the current line, with the body
consisting of zero or more arguments.  If a macro is scoped to the next
line and the line arguments are empty, the next line, which must be
text, is used instead.  Thus:
.Bd -literal -offset indent
\&.I
foo
.Ed
.
.Pp
is equivalent to
.Sq \&.I foo .
If next-line macros are invoked consecutively, only the last is used.
If a next-line macro is followed by a non-next-line macro, an error is
raised (unless in the case of
.Sx \&br ,
.Sx \&sp ,
or
.Sx \&na ) .
.Pp
The syntax is as follows:
.Bd -literal -offset indent
\&.YO \(lBbody...\(rB
\(lBbody...\(rB
.Ed
.
.Pp
.Bl -column -compact -offset indent "MacroX" "ArgumentsX" "ScopeXXXXX" "CompatX"
.It Em Macro Ta Em Arguments Ta Em Scope     Ta Em Notes
.It Sx \&B   Ta    n         Ta    next-line Ta    \&
.It Sx \&BI  Ta    n         Ta    current   Ta    \&
.It Sx \&BR  Ta    n         Ta    current   Ta    \&
.It Sx \&DT  Ta    0         Ta    current   Ta    \&
.It Sx \&I   Ta    n         Ta    next-line Ta    \&
.It Sx \&IB  Ta    n         Ta    current   Ta    \&
.It Sx \&IR  Ta    n         Ta    current   Ta    \&
.\" .It Sx \&PD  Ta    n         Ta    current   Ta    compat
.It Sx \&R   Ta    n         Ta    next-line Ta    \&
.It Sx \&RB  Ta    n         Ta    current   Ta    \&
.It Sx \&RI  Ta    n         Ta    current   Ta    \&
.It Sx \&SB  Ta    n         Ta    next-line Ta    \&
.It Sx \&SM  Ta    n         Ta    next-line Ta    \&
.It Sx \&TH  Ta    >1, <6    Ta    current   Ta    \&
.\" .It Sx \&UC  Ta    n         Ta    current   Ta    compat
.It Sx \&br  Ta    0         Ta    current   Ta    compat
.It Sx \&fi  Ta    0         Ta    current   Ta    compat
.It Sx \&i   Ta    n         Ta    current   Ta    compat
.It Sx \&na  Ta    0         Ta    current   Ta    compat
.It Sx \&nf  Ta    0         Ta    current   Ta    compat
.It Sx \&r   Ta    0         Ta    current   Ta    compat
.It Sx \&sp  Ta    1         Ta    current   Ta    compat
.\" .It Sx \&Sp  Ta    0         Ta    current   Ta    compat
.\" .It Sx \&Vb  Ta    <1        Ta    current   Ta    compat
.\" .It Sx \&Ve  Ta    0         Ta    current   Ta    compat
.El
.
.Pp
Macros marked as
.Qq compat
are included for compatibility with the significant corpus of existing
manuals that mix dialects of roff.  These macros should not be used for
portable
.Nm
manuals.
.
.
.Ss Block Macros
Block macros are comprised of a head and body.  Like for in-line macros,
the head is scoped to the current line and, in one circumstance, the
next line (the next-line stipulations as in
.Sx Line Macros
apply here as well).
.Pp
The syntax is as follows:
.Bd -literal -offset indent
\&.YO \(lBhead...\(rB
\(lBhead...\(rB
\(lBbody...\(rB
.Ed
.
.Pp
The closure of body scope may be to the section, where a macro is closed
by
.Sx \&SH ;
sub-section, closed by a section or
.Sx \&SS ;
part, closed by a section, sub-section, or
.Sx \&RE ;
or paragraph, closed by a section, sub-section, part,
.Sx \&HP ,
.Sx \&IP ,
.Sx \&LP ,
.Sx \&P ,
.Sx \&PP ,
or
.Sx \&TP .
No closure refers to an explicit block closing macro.
.
.Pp
As a rule, block macros may not be nested; thus, calling a block macro
while another block macro scope is open, and the open scope is not
implicitly closed, is syntactically incorrect.
.
.Pp
.Bl -column -compact -offset indent "MacroX" "ArgumentsX" "Head ScopeX" "sub-sectionX" "compatX"
.It Em Macro Ta Em Arguments Ta Em Head Scope Ta Em Body Scope  Ta Em Notes
.It Sx \&HP  Ta    <2        Ta    current    Ta    paragraph   Ta    \&
.It Sx \&IP  Ta    <3        Ta    current    Ta    paragraph   Ta    \&
.It Sx \&LP  Ta    0         Ta    current    Ta    paragraph   Ta    \&
.It Sx \&P   Ta    0         Ta    current    Ta    paragraph   Ta    \&
.It Sx \&PP  Ta    0         Ta    current    Ta    paragraph   Ta    \&
.It Sx \&RE  Ta    0         Ta    current    Ta    none        Ta    compat
.It Sx \&RS  Ta    1         Ta    current    Ta    part        Ta    compat
.It Sx \&SH  Ta    >0        Ta    next-line  Ta    section     Ta    \&
.It Sx \&SS  Ta    >0        Ta    next-line  Ta    sub-section Ta    \&
.It Sx \&TP  Ta    n         Ta    next-line  Ta    paragraph   Ta    \&
.El
.Pp
.
Macros marked
.Qq compat
are as mentioned in
.Sx Line Macros .
.
.Pp
If a block macro is next-line scoped, it may only be followed by in-line
macros for decorating text.
.
.
.Sh REFERENCE
This section is a canonical reference to all macros, arranged
alphabetically.  For the scoping of individual macros, see
.Sx MACRO SYNTAX .
.
.
.Ss \&B
Text is rendered in bold face.
.Pp
See also
.Sx \&I ,
.Sx \&R ,
.Sx \&b ,
.Sx \&i ,
and
.Sx \&r .
.
.
.Ss \&BI
Text is rendered alternately in bold face and italic.  Thus,
.Sq .BI this word and that
causes
.Sq this
and
.Sq and
to render in bold face, while
.Sq word
and
.Sq that
render in italics.  Whitespace between arguments is omitted in output.
.Pp
Examples:
.Pp
.D1 \&.BI bold italic bold italic
.Pp
The output of this example will be emboldened
.Dq bold
and italicised
.Dq italic ,
with spaces stripped between arguments.
.Pp
See also
.Sx \&IB ,
.Sx \&BR ,
.Sx \&RB ,
.Sx \&RI ,
and
.Sx \&IR .
.
.
.Ss \&BR
Text is rendered alternately in bold face and roman (the default font).
Whitespace between arguments is omitted in output.
.Pp
See
.Sx \&BI
for an equivalent example.
.Pp
See also
.Sx \&BI ,
.Sx \&IB ,
.Sx \&RB ,
.Sx \&RI ,
and
.Sx \&IR .
.
.
.Ss \&DT
Has no effect.  Included for compatibility.
.
.
.Ss \&HP
Begin a paragraph whose initial output line is left-justified, but
subsequent output lines are indented, with the following syntax:
.Bd -filled -offset indent
.Pf \. Sx \&HP
.Op Cm width
.Ed
.Pp
The
.Cm width
argument must conform to
.Sx Scaling Widths .
If specified, it's saved for later paragraph left-margins; if unspecified, the
saved or default width is used.
.Pp
See also
.Sx \&IP ,
.Sx \&LP ,
.Sx \&P ,
.Sx \&PP ,
and
.Sx \&TP .
.
.
.Ss \&I
Text is rendered in italics.
.Pp
See also
.Sx \&B ,
.Sx \&R ,
.Sx \&b ,
.Sx \&i ,
and
.Sx \&r .
.
.
.Ss \&IB
Text is rendered alternately in italics and bold face.  Whitespace
between arguments is omitted in output.
.Pp
See
.Sx \&BI
for an equivalent example.
.Pp
See also
.Sx \&BI ,
.Sx \&BR ,
.Sx \&RB ,
.Sx \&RI ,
and
.Sx \&IR .
.
.
.Ss \&IP
Begin an indented paragraph with the following syntax:
.Bd -filled -offset indent
.Pf \. Sx \&IP
.Op Cm head Op Cm width
.Ed
.Pp
The
.Cm width
argument defines the width of the left margin and is defined by
.Sx Scaling Widths ,
It's saved for later paragraph left-margins; if unspecified, the saved or
default width is used.
.Pp
The
.Cm head
argument is used as a leading term, flushed to the left margin.  This is
useful for bulleted paragraphs and so on.
.Pp
See also
.Sx \&HP ,
.Sx \&LP ,
.Sx \&P ,
.Sx \&PP ,
and
.Sx \&TP .
.
.
.Ss \&IR
Text is rendered alternately in italics and roman (the default font).
Whitespace between arguments is omitted in output.
.Pp
See
.Sx \&BI
for an equivalent example.
.Pp
See also
.Sx \&BI ,
.Sx \&IB ,
.Sx \&BR ,
.Sx \&RB ,
and
.Sx \&RI .
.
.
.Ss \&LP
Begin an undecorated paragraph.  The scope of a paragraph is closed by a
subsequent paragraph, sub-section, section, or end of file.  The saved
paragraph left-margin width is re-set to the default.
.Pp
See also
.Sx \&HP ,
.Sx \&IP ,
.Sx \&P ,
.Sx \&PP ,
and
.Sx \&TP .
.
.
.Ss \&P
Synonym for
.Sx \&LP .
.Pp
See also
.Sx \&HP ,
.Sx \&IP ,
.Sx \&LP ,
.Sx \&PP ,
and
.Sx \&TP .
.
.
.Ss \&PP
Synonym for
.Sx \&LP .
.Pp
See also
.Sx \&HP ,
.Sx \&IP ,
.Sx \&LP ,
.Sx \&P ,
and
.Sx \&TP .
.
.
.Ss \&R
Text is rendered in roman (the default font).
.Pp
See also
.Sx \&I ,
.Sx \&B ,
.Sx \&b ,
.Sx \&i ,
and
.Sx \&r .
.
.
.Ss \&RB
Text is rendered alternately in roman (the default font) and bold face.
Whitespace between arguments is omitted in output.
.Pp
See
.Sx \&BI
for an equivalent example.
.Pp
See also
.Sx \&BI ,
.Sx \&IB ,
.Sx \&BR ,
.Sx \&RI ,
and
.Sx \&IR .
.
.
.Ss \&RE
Explicitly close out the scope of a prior
.Sx \&RS .
.
.
.Ss \&RI
Text is rendered alternately in roman (the default font) and italics.
Whitespace between arguments is omitted in output.
.Pp
See
.Sx \&BI
for an equivalent example.
.Pp
See also
.Sx \&BI ,
.Sx \&IB ,
.Sx \&BR ,
.Sx \&RB ,
and
.Sx \&IR .
.
.
.Ss \&RS
Begin a part setting the left margin.  The left margin controls the
offset, following an initial indentation, to un-indented text such as
that of
.Sx \&PP .
This has the following syntax:
.Bd -filled -offset indent
.Pf \. Sx \&Rs
.Op Cm width
.Ed
.Pp
The
.Cm width
argument must conform to
.Sx Scaling Widths .
If not specified, the saved or default width is used.
.
.
.Ss \&SB
Text is rendered in small size (one point smaller than the default font)
bold face.
.
.
.Ss \&SH
Begin a section.  The scope of a section is only closed by another
section or the end of file.  The paragraph left-margin width is re-set
to the default.
.
.
.Ss \&SM
Text is rendered in small size (one point smaller than the default
font).
.
.
.Ss \&SS
Begin a sub-section.  The scope of a sub-section is closed by a
subsequent sub-section, section, or end of file.  The paragraph
left-margin width is re-set to the default.
.
.
.Ss \&TH
Sets the title of the manual page with the following syntax:
.Bd -filled -offset indent
.Pf \. Sx \&TH
.Cm title section
.Op Cm date Op Cm source Op Cm volume
.Ed
.Pp
At least the upper-case document title
.Cm title
and numeric manual section
.Cm section
arguments must be provided.  The
.Cm date
argument should be formatted as described in
.Sx Dates :
if it does not conform, the current date is used instead.  The
.Cm source
string specifies the organisation providing the utility.  The
.Cm volume
string replaces the default rendered volume, which is dictated by the
manual section.
.Pp
Examples:
.Pp
.D1 \&.TH CVS 5 "1992-02-12" GNU
.
.
.Ss \&TP
Begin a paragraph where the head, if exceeding the indentation width, is
followed by a newline; if not, the body follows on the same line after a
buffer to the indentation width.  Subsequent output lines are indented.
The syntax is as follows:
.Bd -filled -offset indent
.Pf \. Sx \&TP
.Op Cm width
.Ed
.Pp
The
.Cm width
argument must conform to
.Sx Scaling Widths .
If specified, it's saved for later paragraph left-margins; if
unspecified, the saved or default width is used.
.Pp
See also
.Sx \&HP ,
.Sx \&IP ,
.Sx \&LP ,
.Sx \&P ,
and
.Sx \&PP .
.\" .
.\" .
.\" .Ss \&PD
.\" Has no effect.  Included for compatibility.
.\" .
.\" .
.\" .Ss \&UC
.\" Has no effect.  Included for compatibility.
.
.
.Ss \&br
Breaks the current line.  Consecutive invocations have no further effect.
.Pp
See also
.Sx \&sp .
.
.
.Ss \&fi
End literal mode begun by
.Sx \&nf .
.
.
.Ss \&i
Italicise arguments.  Synonym for
.Sx \&I .
.Pp
See also
.Sx \&B ,
.Sx \&I ,
.Sx \&R .
.Sx \&b ,
and
.Sx \&r .
.
.
.Ss \&na
Don't align to the right margin.
.
.
.Ss \&nf
Begin literal mode: all subsequent free-form lines have their end of
line boundaries preserved.  May be ended by
.Sx \&fi .
.
.
.Ss \&r
Fonts and styles (bold face, italics) reset to roman (default font).
.Pp
See also
.Sx \&B ,
.Sx \&I ,
.Sx \&R ,
.Sx \&b ,
and
.Sx \&i .
.
.
.Ss \&sp
Insert vertical spaces into output with the following syntax:
.Bd -filled -offset indent
.Pf \. Sx \&sp
.Op Cm height
.Ed
.Pp
Insert
.Cm height
spaces, which must conform to
.Sx Scaling Widths .
If 0, this is equivalent to the
.Sx \&br
macro.  Defaults to 1, if unspecified.
.Pp
See also
.Sx \&br .
.
.\" .Ss \&Sp
.\" A synonym for
.\" .Sx \&sp
.\" .Cm 0.5v .
.\" .
.\" .Ss \&Vb
.\" A synonym for
.\" .Sx \&nf .
.\" Accepts an argument (the height of the formatted space) which is
.\" disregarded.
.\" .
.\" .Ss \&Ve
.\" A synonym for
.\" .Sx \&fi .
.\" .
.
.Sh COMPATIBILITY
This section documents areas of questionable portability between
implementations of the
.Nm
language.
.
.Pp
.Bl -dash -compact
.It
In quoted literals, GNU troff allowed pair-wise double-quotes to produce
a standalone double-quote in formatted output.  It is not known whether
this behaviour is exhibited by other formatters.
.
.It
Blocks of whitespace are stripped from macro and free-form text lines
(except when in literal mode) in mandoc.  This is not the case for GNU
troff: for maximum portability, whitespace sensitive blocks should be
enclosed in literal contexts.
.
.It
The
.Sx \&sp
macro does not accept negative values in mandoc.  In GNU troff, this
would result in strange behaviour.
.
.It
The
.Sq \(aq
macro control character, in GNU troff (and prior troffs) suppresses a
newline before macro output; in mandoc, it is an alias for the standard
.Sq \&.
control character.
.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 .
.
.
.Sh CAVEATS
Do not use this language.  Use
.Xr mdoc 7 ,
instead.
.