Minimal implementation of the read-only number register \n(.$

[mandoc.git] / roff.7

.\"     $Id: roff.7,v 1.72 2015/05/31 23:13:22 schwarze Exp $
.\"
.\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
.\" Copyright (c) 2010, 2011, 2013, 2014 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: May 31 2015 $
.Dt ROFF 7
.Os
.Sh NAME
.Nm roff
.Nd roff language reference for mandoc
.Sh DESCRIPTION
The
.Nm roff
language is a general purpose text formatting language.
Since traditional implementations of the
.Xr mdoc 7
and
.Xr man 7
manual formatting languages are based on it,
many real-world manuals use small numbers of
.Nm
requests and escape sequences intermixed with their
.Xr mdoc 7
or
.Xr man 7
code.
To properly format such manuals, the
.Xr mandoc 1
utility supports a tiny subset of
.Nm
requests and escapes.
Only these requests and escapes supported by
.Xr mandoc 1
are documented in the present manual,
together with the basic language syntax shared by
.Nm ,
.Xr mdoc 7 ,
and
.Xr man 7 .
For complete
.Nm
manuals, consult the
.Sx SEE ALSO
section.
.Pp
Input lines beginning with the control character
.Sq \&.
are parsed for requests and macros.
Such lines are called
.Dq request lines
or
.Dq macro lines ,
respectively.
Requests change the processing state and manipulate the formatting;
some macros also define the document structure and produce formatted
output.
The single quote
.Pq Qq \(aq
is accepted as an alternative control character,
treated by
.Xr mandoc 1
just like
.Ql \&.
.Pp
Lines not beginning with control characters are called
.Dq text lines .
They provide free-form text to be printed; the formatting of the text
depends on the respective processing context.
.Sh LANGUAGE SYNTAX
.Nm
documents may contain only graphable 7-bit ASCII characters, the space
character, and, in certain circumstances, the tab character.
The backslash character
.Sq \e
indicates the start of an escape sequence, used for example for
.Sx Comments ,
.Sx Special Characters ,
.Sx Predefined Strings ,
and
user-defined strings defined using the
.Sx ds
request.
For a listing of escape sequences, consult the
.Sx ESCAPE SEQUENCE REFERENCE
below.
.Ss Comments
Text following an escaped double-quote
.Sq \e\(dq ,
whether in a request, macro, or text line, is ignored to the end of the line.
A request line beginning with a control character and comment escape
.Sq \&.\e\(dq
is also ignored.
Furthermore, request lines with only a control character and optional
trailing whitespace are stripped from input.
.Pp
Examples:
.Bd -literal -offset indent -compact
\&.\e\(dq This is a comment line.
\&.\e\(dq The next line is ignored:
\&.
\&.Sh EXAMPLES \e\(dq This is a comment, too.
\&example text \e\(dq And so is this.
.Ed
.Ss Special Characters
Special characters are used to encode special glyphs and are rendered
differently across output media.
They may occur in request, macro, and text 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.
.Pp
Examples:
.Bl -tag -width Ds -offset indent -compact
.It Li \e(em
Two-letter em dash escape.
.It Li \ee
One-letter backslash escape.
.El
.Pp
See
.Xr mandoc_char 7
for a complete list.
.Ss Text Decoration
Terms may be text-decorated using the
.Sq \ef
escape followed by an indicator: B (bold), I (italic), R (regular), or P
(revert to previous mode).
A numerical representation 3, 2, or 1 (bold, italic, and regular,
respectively) may be used instead.
The indicator or numerical representative may be preceded by C
(constant-width), which is ignored.
.Pp
The two-character indicator
.Sq BI
requests a font that is both bold and italic.
It may not be portable to old roff implementations.
.Pp
Examples:
.Bl -tag -width Ds -offset indent -compact
.It Li \efBbold\efR
Write in \fBbold\fP, then switch to regular font mode.
.It Li \efIitalic\efP
Write in \fIitalic\fP, then return to previous font mode.
.It Li \ef(BIbold italic\efP
Write in \f(BIbold italic\fP, then return to previous font mode.
.El
.Pp
Text decoration is
.Em not
recommended for
.Xr mdoc 7 ,
which encourages semantic annotation.
.Ss Predefined Strings
Predefined strings, like
.Sx Special Characters ,
mark special output glyphs.
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] .
.Pp
Examples:
.Bl -tag -width Ds -offset indent -compact
.It Li \e*(Am
Two-letter ampersand predefined string.
.It Li \e*q
One-letter double-quote predefined string.
.El
.Pp
Predefined strings are not recommended for use,
as they differ across implementations.
Those supported by
.Xr mandoc 1
are listed in
.Xr mandoc_char 7 .
Manuals using these predefined strings are almost certainly not portable.
.Ss Whitespace
Whitespace consists of the space character.
In text lines, whitespace is preserved within a line.
In request and macro lines, whitespace delimits arguments and is discarded.
.Pp
Unescaped trailing spaces are stripped from text line input unless in a
literal context.
In general, trailing whitespace on any input line is discouraged for
reasons of portability.
In the rare case that a blank character is needed at the end of an
input line, it may be forced by
.Sq \e\ \e& .
.Pp
Literal space characters can be produced in the output
using escape sequences.
In macro lines, they can also be included in arguments using quotation; see
.Sx MACRO SYNTAX
for details.
.Pp
Blank text lines, which may include whitespace, are only permitted
within literal contexts.
If the first character of a text line is a space, that line is printed
with a leading newline.
.Ss Scaling Widths
Many requests and macros support scaled widths for their arguments.
The syntax for a scaled width is
.Sq Li [+-]?[0-9]*.[0-9]*[:unit:] ,
where a decimal must be preceded or followed by at least one digit.
Negative numbers, while accepted, are truncated to zero.
.Pp
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
scale
.Sq u
by 65536
.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 for the terminal
.It M
mini-em (~1/100 em)
.El
.Pp
Using anything other than
.Sq m ,
.Sq n ,
or
.Sq v
is necessarily non-portable across output media.
See
.Sx COMPATIBILITY .
.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.
.Pp
Examples:
.Bl -tag -width ".Bl -tag -width 2i" -offset indent -compact
.It Li \&.Bl -tag -width 2i
two-inch tagged list indentation in
.Xr mdoc 7
.It Li \&.HP 2i
two-inch tagged list indentation in
.Xr man 7
.It Li \&.sp 2v
two vertical spaces
.El
.Ss Sentence Spacing
Each sentence should terminate at the end of an input line.
By doing this, a formatter 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
.Po
.Sq \&) ,
.Sq \&] ,
.Sq \&' ,
.Sq \&"
.Pc .
.Pp
The proper spacing is also intelligently preserved if a sentence ends at
the boundary of a macro line.
.Pp
Examples:
.Bd -literal -offset indent -compact
Do not end sentences mid-line like this.  Instead,
end a sentence like this.
A macro would end like this:
\&.Xr mandoc 1 \&.
.Ed
.Sh REQUEST SYNTAX
A request or macro line consists of:
.Pp
.Bl -enum -compact
.It
the control character
.Sq \&.
or
.Sq \(aq
at the beginning of the line,
.It
optionally an arbitrary amount of whitespace,
.It
the name of the request or the macro, which is one word of arbitrary
length, terminated by whitespace,
.It
and zero or more arguments delimited by whitespace.
.El
.Pp
Thus, the following request lines are all equivalent:
.Bd -literal -offset indent
\&.ig end
\&.ig    end
\&.   ig end
.Ed
.Sh MACRO SYNTAX
Macros are provided by the
.Xr mdoc 7
and
.Xr man 7
languages and can be defined by the
.Sx \&de
request.
When called, they follow the same syntax as requests, except that
macro arguments may optionally be quoted by enclosing them
in double quote characters
.Pq Sq \(dq .
Quoted text, even if it contains whitespace or would cause
a macro invocation when unquoted, is always considered literal text.
Inside quoted text, pairs of double quote characters
.Pq Sq Qq
resolve to single double quote characters.
.Pp
To be recognised as the beginning of a quoted argument, the opening
quote character must be preceded by a space character.
A quoted argument extends to the next double quote character that is not
part of a pair, or to the end of the input line, whichever comes earlier.
Leaving out the terminating double quote character at the end of the line
is discouraged.
For clarity, if more arguments follow on the same input line,
it is recommended to follow the terminating double quote character
by a space character; in case the next character after the terminating
double quote character is anything else, it is regarded as the beginning
of the next, unquoted argument.
.Pp
Both in quoted and unquoted arguments, pairs of backslashes
.Pq Sq \e\e
resolve to single backslashes.
In unquoted arguments, space characters can alternatively be included
by preceding them with a backslash
.Pq Sq \e\~ ,
but quoting is usually better for clarity.
.Pp
Examples:
.Bl -tag -width Ds -offset indent -compact
.It Li .Fn strlen \(dqconst char *s\(dq
Group arguments
.Qq const char *s
into one function argument.
If unspecified,
.Qq const ,
.Qq char ,
and
.Qq *s
would be considered separate arguments.
.It Li .Op \(dqFl a\(dq
Consider
.Qq \&Fl a
as literal text instead of a flag macro.
.El
.Sh REQUEST REFERENCE
The
.Xr mandoc 1
.Nm
parser recognises the following requests.
For requests marked as "ignored" or "unsupported", any arguments are
ignored, and the number of arguments is not checked.
.Ss \&ab
Abort processing.
Currently unsupported.
.Ss \&ad
Set line adjustment mode.
It takes one argument to select normal, left, right,
or center adjustment for subsequent text.
Currently ignored.
.Ss \&af
Assign an output format to a number register.
Currently ignored.
.Ss \&aln
Create an alias for a number register.
Currently unsupported.
.Ss \&als
Create an alias for a request, string, macro, or diversion.
Currently unsupported.
.Ss \&am
Append to a macro definition.
The syntax of this request is the same as that of
.Sx \&de .
.Ss \&am1
Append to a macro definition, switching roff compatibility mode off
during macro execution (groff extension).
The syntax of this request is the same as that of
.Sx \&de1 .
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Sx \&am .
.Ss \&ami
Append to a macro definition, specifying the macro name indirectly
(groff extension).
The syntax of this request is the same as that of
.Sx \&dei .
.Ss \&ami1
Append to a macro definition, specifying the macro name indirectly
and switching roff compatibility mode off during macro execution
(groff extension).
The syntax of this request is the same as that of
.Sx \&dei1 .
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Sx \&ami .
.Ss \&as
Append to a user-defined string.
The syntax of this request is the same as that of
.Sx \&ds .
If a user-defined string with the specified name does not yet exist,
it is set to the empty string before appending.
.Ss \&as1
Append to a user-defined string, switching roff compatibility mode off
during macro execution (groff extension).
The syntax of this request is the same as that of
.Sx \&ds1 .
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Sx \&as .
.Ss \&asciify
Fully unformat a diversion.
Currently unsupported.
.Ss \&backtrace
Print a backtrace of the input stack.
This is a groff extension and currently ignored.
.Ss \&bd
Artificially embolden by repeated printing with small shifts.
Currently ignored.
.Ss \&bleedat
Set the BleedBox page parameter for PDF generation.
This is a Heirloom extension and currently ignored.
.Ss \&blm
Set a blank line trap.
Currently unsupported.
.Ss \&box
Begin a diversion without including a partially filled line.
Currently unsupported.
.Ss \&boxa
Add to a diversion without including a partially filled line.
Currently unsupported.
.Ss \&bp
Begin new page.
Currently ignored.
.Ss \&BP
Define a frame and place a picture in it.
This is a Heirloom extension and currently unsupported.
.Ss \&br
Break the output line.
See
.Xr man 7
and
.Xr mdoc 7 .
.Ss \&break
Break out of a
.Sx \&while
loop.
Currently unsupported.
.Ss \&breakchar
Optional line break characters.
This is a Heirloom extension and currently ignored.
.Ss \&brnl
Break output line after next N input lines.
This is a Heirloom extension and currently ignored.
.Ss \&brp
Break and spread output line.
Currently, this is implemented as an alias for
.Sx \&br .
.Ss \&brpnl
Break and spread output line after next N input lines.
This is a Heirloom extension and currently ignored.
.Ss \&c2
Change the no-break control character.
Currently unsupported.
.Ss \&cc
Change the control character.
Its syntax is as follows:
.Bd -literal -offset indent
.Pf . Cm \&cc Op Ar c
.Ed
.Pp
If
.Ar c
is not specified, the control character is reset to
.Sq \&. .
Trailing characters are ignored.
.Ss \&ce
Center some lines.
It takes one integer argument, specifying how many lines to center.
Currently ignored.
.Ss \&cf
Output the contents of a file.
Ignored because insecure.
.Ss \&cflags
Set character flags.
This is a groff extension and currently ignored.
.Ss \&ch
Change a trap location.
Currently ignored.
.Ss \&char
Define a new glyph.
Currently unsupported.
.Ss \&chop
Remove the last character from a macro, string, or diversion.
Currently unsupported.
.Ss \&class
Define a character class.
This is a groff extension and currently ignored.
.Ss \&close
Close an open file.
Ignored because insecure.
.Ss \&CL
Print text in color.
This is a Heirloom extension and currently unsupported.
.Ss \&color
Activate or deactivate colors.
This is a groff extension and currently ignored.
.Ss \&composite
Define a name component for composite glyph names.
This is a groff extension and currently unsupported.
.Ss \&continue
Immediately start the next iteration of a
.Sx \&while
loop.
Currently unsupported.
.Ss \&cp
Switch
.Nm
compatibility mode on or off.
Currently ignored.
.Ss \&cropat
Set the CropBox page parameter for PDF generation.
This is a Heirloom extension and currently ignored.
.Ss \&cs
Constant character spacing mode.
Currently ignored.
.Ss \&cu
Underline including whitespace.
Currently ignored.
.Ss \&da
Append to a diversion.
Currently unsupported.
.Ss \&dch
Change a trap location in the current diversion.
This is a Heirloom extension and currently unsupported.
.Ss \&de
Define a
.Nm
macro.
Its syntax can be either
.Bd -literal -offset indent
.Pf . Cm \&de Ar name
.Ar macro definition
\&..
.Ed
.Pp
or
.Bd -literal -offset indent
.Pf . Cm \&de Ar name Ar end
.Ar macro definition
.Pf . Ar end
.Ed
.Pp
Both forms define or redefine the macro
.Ar name
to represent the
.Ar macro definition ,
which may consist of one or more input lines, including the newline
characters terminating each line, optionally containing calls to
.Nm
requests,
.Nm
macros or high-level macros like
.Xr man 7
or
.Xr mdoc 7
macros, whichever applies to the document in question.
.Pp
Specifying a custom
.Ar end
macro works in the same way as for
.Sx \&ig ;
namely, the call to
.Sq Pf . Ar end
first ends the
.Ar macro definition ,
and after that, it is also evaluated as a
.Nm
request or
.Nm
macro, but not as a high-level macro.
.Pp
The macro can be invoked later using the syntax
.Pp
.D1 Pf . Ar name Op Ar argument Op Ar argument ...
.Pp
Regarding argument parsing, see
.Sx MACRO SYNTAX
above.
.Pp
The line invoking the macro will be replaced
in the input stream by the
.Ar macro definition ,
replacing all occurrences of
.No \e\e$ Ns Ar N ,
where
.Ar N
is a digit, by the
.Ar N Ns th Ar argument .
For example,
.Bd -literal -offset indent
\&.de ZN
\efI\e^\e\e$1\e^\efP\e\e$2
\&..
\&.ZN XtFree .
.Ed
.Pp
produces
.Pp
.D1 \efI\e^XtFree\e^\efP.
.Pp
in the input stream, and thus in the output: \fI\^XtFree\^\fP.
.Pp
Since macros and user-defined strings share a common string table,
defining a macro
.Ar name
clobbers the user-defined string
.Ar name ,
and the
.Ar macro definition
can also be printed using the
.Sq \e*
string interpolation syntax described below
.Sx ds ,
but this is rarely useful because every macro definition contains at least
one explicit newline character.
.Pp
In order to prevent endless recursion, both groff and
.Xr mandoc 1
limit the stack depth for expanding macros and strings
to a large, but finite number, and
.Xr mandoc 1
also limits the length of the expanded input line.
Do not rely on the exact values of these limits.
.Ss \&de1
Define a
.Nm
macro that will be executed with
.Nm
compatibility mode switched off during macro execution.
This is a groff extension.
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Sx \&de .
.Ss \&defcolor
Define a color name.
This is a groff extension and currently ignored.
.Ss \&dei
Define a
.Nm
macro, specifying the macro name indirectly (groff extension).
The syntax of this request is the same as that of
.Sx \&de .
The request
.Pp
.D1 Pf . Cm \&dei Ar name Op Ar end
.Pp
has the same effect as:
.Pp
.D1 Pf . Cm \&de No \e* Ns Bo Ar name Bc Op \e* Ns Bq Ar end
.Ss \&dei1
Define a
.Nm
macro that will be executed with
.Nm
compatibility mode switched off during macro execution,
specifying the macro name indirectly (groff extension).
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Sx \&dei .
.Ss \&device
This request only makes sense with the groff-specific intermediate
output format and is unsupported.
.Ss \&devicem
This request only makes sense with the groff-specific intermediate
output format and is unsupported.
.Ss \&di
Begin a diversion.
Currently unsupported.
.Ss \&do
Execute
.Nm
request or macro line with compatibility mode disabled.
Currently unsupported.
.Ss \&ds
Define a user-defined string.
Its syntax is as follows:
.Pp
.D1 Pf . Cm \&ds Ar name Oo \(dq Oc Ns Ar string
.Pp
The
.Ar name
and
.Ar string
arguments are space-separated.
If the
.Ar string
begins with a double-quote character, that character will not be part
of the string.
All remaining characters on the input line form the
.Ar string ,
including whitespace and double-quote characters, even trailing ones.
.Pp
The
.Ar string
can be interpolated into subsequent text by using
.No \e* Ns Bq Ar name
for a
.Ar name
of arbitrary length, or \e*(NN or \e*N if the length of
.Ar name
is two or one characters, respectively.
Interpolation can be prevented by escaping the leading backslash;
that is, an asterisk preceded by an even number of backslashes
does not trigger string interpolation.
.Pp
Since user-defined strings and macros share a common string table,
defining a string
.Ar name
clobbers the macro
.Ar name ,
and the
.Ar name
used for defining a string can also be invoked as a macro,
in which case the following input line will be appended to the
.Ar string ,
forming a new input line passed to the
.Nm
parser.
For example,
.Bd -literal -offset indent
\&.ds badidea .S
\&.badidea
H SYNOPSIS
.Ed
.Pp
invokes the
.Cm SH
macro when used in a
.Xr man 7
document.
Such abuse is of course strongly discouraged.
.Ss \&ds1
Define a user-defined string that will be expanded with
.Nm
compatibility mode switched off during string expansion.
This is a groff extension.
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Sx \&ds .
.Ss \&dwh
Set a location trap in the current diversion.
This is a Heirloom extension and currently unsupported.
.Ss \&dt
Set a trap within a diversion.
Currently unsupported.
.Ss \&ec
Change the escape character.
Currently unsupported.
.Ss \&ecs
Restore the escape character.
Currently unsupported.
.Ss \&ecr
Save the escape character.
Currently unsupported.
.Ss \&el
The
.Qq else
half of an if/else conditional.
Pops a result off the stack of conditional evaluations pushed by
.Sx \&ie
and uses it as its conditional.
If no stack entries are present (e.g., due to no prior
.Sx \&ie
calls)
then false is assumed.
The syntax of this request is similar to
.Sx \&if
except that the conditional is missing.
.Ss \&em
Set a trap at the end of input.
Currently unsupported.
.Ss \&EN
End an equation block.
See
.Sx \&EQ .
.Ss \&eo
Disable the escape mechanism completely.
Currently unsupported.
.Ss \&EP
End a picture started by
.Sx \&BP .
This is a Heirloom extension and currently unsupported.
.Ss \&EQ
Begin an equation block.
See
.Xr eqn 7
for a description of the equation language.
.Ss \&errprint
Print a string like an error message.
This is a Heirloom extension and currently ignored.
.Ss \&ev
Switch to another environment.
Currently unsupported.
.Ss \&evc
Copy an environment into the current environment.
Currently unsupported.
.Ss \&ex
Abort processing and exit.
Currently unsupported.
.Ss \&fallback
Select the fallback sequence for a font.
This is a Heirloom extension and currently ignored.
.Ss \&fam
Change the font family.
Takes one argument specifying the font family to be selected.
It is a groff extension and currently ignored.
.Ss \&fc
Define a delimiting and a padding character for fields.
Currently unsupported.
.Ss \&fchar
Define a fallback glyph.
Currently unsupported.
.Ss \&fcolor
Set the fill color for \eD objects.
This is a groff extension and currently ignored.
.Ss \&fdeferlig
Defer ligature building.
This is a Heirloom extension and currently ignored.
.Ss \&feature
Enable or disable an OpenType feature.
This is a Heirloom extension and currently ignored.
.Ss \&fi
Switch to fill mode.
See
.Xr man 7 .
Ignored in
.Xr mdoc 7 .
.Ss \&fkern
Control the use of kerning tables for a font.
This is a Heirloom extension and currently ignored.
.Ss \&fl
Flush output.
Currently ignored.
.Ss \&flig
Define ligatures.
This is a Heirloom extension and currently ignored.
.Ss \&fp
Assign font position.
Currently ignored.
.Ss \&fps
Mount a font with a special character map.
This is a Heirloom extension and currently ignored.
.Ss \&fschar
Define a font-specific fallback glyph.
This is a groff extension and currently unsupported.
.Ss \&fspacewidth
Set a font-specific width for the space character.
This is a Heirloom extension and currently ignored.
.Ss \&fspecial
Conditionally define a special font.
This is a groff extension and currently ignored.
.Ss \&ft
Change the font.
Its syntax is as follows:
.Pp
.D1 Pf . Cm \&ft Op Ar font
.Pp
The following
.Ar font
arguments are supported:
.Bl -tag -width 4n -offset indent
.It Cm B , BI , 3 , 4
switches to
.Sy bold
font
.It Cm I , 2
switches to
.Em underlined
font
.It Cm R , CW , 1
switches to normal font
.It Cm P No "or no argument"
switches back to the previous font
.El
.Pp
This request takes effect only locally, may be overridden by macros
and escape sequences, and is only supported in
.Xr man 7
for now.
.Ss \&ftr
Translate font name.
This is a groff extension and currently ignored.
.Ss \&fzoom
Zoom font size.
Currently ignored.
.Ss \&gcolor
Set glyph color.
This is a groff extension and currently ignored.
.Ss \&hc
Set the hyphenation character.
Currently ignored.
.Ss \&hcode
Set hyphenation codes of characters.
Currently ignored.
.Ss \&hidechar
Hide characters in a font.
This is a Heirloom extension and currently ignored.
.Ss \&hla
Set hyphenation language.
This is a groff extension and currently ignored.
.Ss \&hlm
Set maximum number of consecutive hyphenated lines.
Currently ignored.
.Ss \&hpf
Load hyphenation pattern file.
This is a groff extension and currently ignored.
.Ss \&hpfa
Load hyphenation pattern file, appending to the current patterns.
This is a groff extension and currently ignored.
.Ss \&hpfcode
Define mapping values for character codes in hyphenation patterns.
This is a groff extension and currently ignored.
.Ss \&hw
Specify hyphenation points in words.
Currently ignored.
.Ss \&hy
Set automatic hyphenation mode.
Currently ignored.
.Ss \&hylang
Set hyphenation language.
This is a Heirloom extension and currently ignored.
.Ss \&hylen
Minimum word length for hyphenation.
This is a Heirloom extension and currently ignored.
.Ss \&hym
Set hyphenation margin.
This is a groff extension and currently ignored.
.Ss \&hypp
Define hyphenation penalties.
This is a Heirloom extension and currently ignored.
.Ss \&hys
Set hyphenation space.
This is a groff extension and currently ignored.
.Ss \&ie
The
.Qq if
half of an if/else conditional.
The result of the conditional is pushed into a stack used by subsequent
invocations of
.Sx \&el ,
which may be separated by any intervening input (or not exist at all).
Its syntax is equivalent to
.Sx \&if .
.Ss \&if
Begins a conditional.
This request has the following syntax:
.Bd -literal -offset indent
\&.if COND BODY
.Ed
.Bd -literal -offset indent
\&.if COND \e{BODY
BODY...\e}
.Ed
.Bd -literal -offset indent
\&.if COND \e{\e
BODY...
\&.\e}
.Ed
.Pp
COND is a conditional statement.
Currently,
.Xr mandoc 1
supports the following subset of roff conditionals:
.Bl -bullet
.It
If
.Sq \&!
is prefixed to COND, the condition is logically inverted.
.It
If the first character of COND is
.Sq n
.Pq nroff mode
or
.Sq o
.Pq odd page ,
COND evaluates to true.
.It
If the first character of COND is
.Sq c
.Pq character available ,
.Sq d
.Pq string defined ,
.Sq e
.Pq even page ,
.Sq t
.Pq troff mode ,
or
.Sq v
.Pq vroff mode ,
COND evaluates to false.
.It
If the first character of COND is
.Sq r ,
it evalutes to true if the rest of COND is the name of an existing
number register; otherwise, it evaluates to false.
.It
If COND starts with a parenthesis or with an optionally signed
integer number, it is evaluated according to the rules of
.Sx Numerical expressions
explained below.
It evaluates to true if the result is positive,
or to false if the result is zero or negative.
.It
Otherwise, the first character of COND is regarded as a delimiter
and COND evaluates to true if the string extending from its first
to its second occurrence is equal to the string extending from its
second to its third occurrence.
.It
If COND cannot be parsed, it evaluates to false.
.El
.Pp
If a conditional is false, its children are not processed, but are
syntactically interpreted to preserve the integrity of the input
document.
Thus,
.Pp
.D1 \&.if t .ig
.Pp
will discard the
.Sq \&.ig ,
which may lead to interesting results, but
.Pp
.D1 \&.if t .if t \e{\e
.Pp
will continue to syntactically interpret to the block close of the final
conditional.
Sub-conditionals, in this case, obviously inherit the truth value of
the parent.
.Pp
If the BODY section is begun by an escaped brace
.Sq \e{ ,
scope continues until the end of the input line containing the
matching closing-brace escape sequence
.Sq \e} .
If the BODY is not enclosed in braces, scope continues until
the end of the line.
If the COND is followed by a BODY on the same line, whether after a
brace or not, then requests and macros
.Em must
begin with a control character.
It is generally more intuitive, in this case, to write
.Bd -literal -offset indent
\&.if COND \e{\e
\&.foo
bar
\&.\e}
.Ed
.Pp
than having the request or macro follow as
.Pp
.D1 \&.if COND \e{ .foo
.Pp
The scope of a conditional is always parsed, but only executed if the
conditional evaluates to true.
.Pp
Note that the
.Sq \e}
is converted into a zero-width escape sequence if not passed as a
standalone macro
.Sq \&.\e} .
For example,
.Pp
.D1 \&.Fl a \e} b
.Pp
will result in
.Sq \e}
being considered an argument of the
.Sq \&Fl
macro.
.Ss \&ig
Ignore input.
Its syntax can be either
.Bd -literal -offset indent
.Pf . Cm \&ig
.Ar ignored text
\&..
.Ed
.Pp
or
.Bd -literal -offset indent
.Pf . Cm \&ig Ar end
.Ar ignored text
.Pf . Ar end
.Ed
.Pp
In the first case, input is ignored until a
.Sq \&..
request is encountered on its own line.
In the second case, input is ignored until the specified
.Sq Pf . Ar end
macro is encountered.
Do not use the escape character
.Sq \e
anywhere in the definition of
.Ar end ;
it would cause very strange behaviour.
.Pp
When the
.Ar end
macro is a roff request or a roff macro, like in
.Pp
.D1 \&.ig if
.Pp
the subsequent invocation of
.Sx \&if
will first terminate the
.Ar ignored text ,
then be invoked as usual.
Otherwise, it only terminates the
.Ar ignored text ,
and arguments following it or the
.Sq \&..
request are discarded.
.Ss \&in
Change indentation.
See
.Xr man 7 .
Ignored in
.Xr mdoc 7 .
.Ss \&index
Find a substring in a string.
This is a Heirloom extension and currently unsupported.
.Ss \&it
Set an input line trap.
Its syntax is as follows:
.Pp
.D1 Pf . Cm it Ar expression macro
.Pp
The named
.Ar macro
will be invoked after processing the number of input text lines
specified by the numerical
.Ar expression .
While evaluating the
.Ar expression ,
the unit suffixes described below
.Sx Scaling Widths
are ignored.
.Ss \&itc
Set an input line trap, not counting lines ending with \ec.
Currently unsupported.
.Ss \&IX
To support the generation of a table of contents,
.Xr pod2man 1
emits this user-defined macro, usually without defining it.
To avoid reporting large numbers of spurious errors,
.Xr mandoc 1
ignores it.
.Ss \&kern
Switch kerning on or off.
Currently ignored.
.Ss \&kernafter
Increase kerning after some characters.
This is a Heirloom extension and currently ignored.
.Ss \&kernbefore
Increase kerning before some characters.
This is a Heirloom extension and currently ignored.
.Ss \&kernpair
Add a kerning pair to the kerning table.
This is a Heirloom extension and currently ignored.
.Ss \&lc
Define a leader repetition character.
Currently unsupported.
.Ss \&lc_ctype
Set the
.Dv LC_CTYPE
locale.
This is a Heirloom extension and currently unsupported.
.Ss \&lds
Define a local string.
This is a Heirloom extension and currently unsupported.
.Ss \&length
Count the number of input characters in a user-defined string.
Currently unsupported.
.Ss \&letadj
Dynamic letter spacing and reshaping.
This is a Heirloom extension and currently ignored.
.Ss \&lf
Change the line number for error messages.
Ignored because insecure.
.Ss \&lg
Switch the ligature mechanism on or off.
Currently ignored.
.Ss \&lhang
Hang characters at left margin.
This is a Heirloom extension and currently ignored.
.Ss \&linetabs
Enable or disable line-tabs mode.
This is a groff extension and currently unsupported.
.Ss \&ll
Change the output line length.
Its syntax is as follows:
.Pp
.D1 Pf . Cm \&ll Op Oo +|- Oc Ns Ar width
.Pp
If the
.Ar width
argument is omitted, the line length is reset to its previous value.
The default setting for terminal output is 78n.
If a sign is given, the line length is added to or subtracted from;
otherwise, it is set to the provided value.
Using this request in new manuals is discouraged for several reasons,
among others because it overrides the
.Xr mandoc 1
.Fl O Cm width
command line option.
.Ss \&lnr
Set local number register.
This is a Heirloom extension and currently unsupported.
.Ss \&lnrf
Set local floating-point register.
This is a Heirloom extension and currently unsupported.
.Ss \&lpfx
Set a line prefix.
This is a Heirloom extension and currently unsupported.
.Ss \&ls
Set line spacing.
It takes one integer argument specifying the vertical distance of
subsequent output text lines measured in v units.
Currently ignored.
.Ss \&lsm
Set a leading spaces trap.
This is a groff extension and currently unsupported.
.Ss \&lt
Set title line length.
Currently ignored.
.Ss \&mc
Print margin character in the right margin.
Currently ignored.
.Ss \&mediasize
Set the device media size.
This is a Heirloom extension and currently ignored.
.Ss \&minss
Set minimum word space.
This is a Heirloom extension and currently ignored.
.Ss \&mk
Mark vertical position.
Currently ignored.
.Ss \&mso
Load a macro file.
Ignored because insecure.
.Ss \&na
Disable adjusting without changing the adjustment mode.
Currently ignored.
.Ss \&ne
Declare the need for the specified minimum vertical space
before the next trap or the bottom of the page.
Currently ignored.
.Ss \&nf
Switch to no-fill mode.
See
.Xr man 7 .
Ignored by
.Xr mdoc 7 .
.Ss \&nh
Turn off automatic hyphenation mode.
Currently ignored.
.Ss \&nhychar
Define hyphenation-inhibiting characters.
This is a Heirloom extension and currently ignored.
.Ss \&nm
Print line numbers.
Currently unsupported.
.Ss \&nn
Temporarily turn off line numbering.
Currently unsupported.
.Ss \&nop
Exexute the rest of the input line as a request or macro line.
Currently unsupported.
.Ss \&nr
Define or change a register.
A register is an arbitrary string value that defines some sort of state,
which influences parsing and/or formatting.
Its syntax is as follows:
.Pp
.D1 Pf \. Cm \&nr Ar name Oo +|- Oc Ns Ar expression
.Pp
For the syntax of
.Ar expression ,
see
.Sx Numerical expressions
below.
If it is prefixed by a sign, the register will be
incremented or decremented instead of assigned to.
.Pp
The following register
.Ar name
is handled specially:
.Bl -tag -width Ds
.It Cm nS
If set to a positive integer value, certain
.Xr mdoc 7
macros will behave in the same way as in the
.Em SYNOPSIS
section.
If set to 0, these macros will behave in the same way as outside the
.Em SYNOPSIS
section, even when called within the
.Em SYNOPSIS
section itself.
Note that starting a new
.Xr mdoc 7
section with the
.Cm \&Sh
macro will reset this register.
.El
.Ss \&nrf
Define or change a floating-point register.
This is a Heirloom extension and currently unsupported.
.Ss \&nroff
Force nroff mode.
This is a groff extension and currently ignored.
.Ss \&ns
Turn on no-space mode.
Currently ignored.
.Ss \&nx
Abort processing of the current input file and process another one.
Ignored because insecure.
.Ss \&open
Open a file for writing.
Ignored because insecure.
.Ss \&opena
Open a file for appending.
Ignored because insecure.
.Ss \&os
Output saved vertical space.
Currently ignored.
.Ss \&output
Output directly to intermediate output.
Not supported.
.Ss \&padj
Globally control paragraph-at-once adjustment.
This is a Heirloom extension and currently ignored.
.Ss \&papersize
Set the paper size.
This is a Heirloom extension and currently ignored.
.Ss \&pc
Change the page number character.
Currently ignored.
.Ss \&pev
Print environments.
This is a groff extension and currently ignored.
.Ss \&pi
Pipe output to a shell command.
Ignored because insecure.
.Ss \&PI
Low-level request used by
.Sx \&BP .
This is a Heirloom extension and currently unsupported.
.Ss \&pl
Change page length.
Takes one height argument.
Currently ignored.
.Ss \&pm
Print names and sizes of macros, strings, and diversions.
Currently ignored.
.Ss \&pn
Change page number of the next page.
Currently ignored.
.Ss \&pnr
Print all number registers.
Currently ignored.
.Ss \&po
Set horizontal page offset.
Currently ignored.
.Ss \&ps
Change point size.
Takes one numerical argument.
Currently ignored.
.Ss \&psbb
Retrieve the bounding box of a PostScript file.
Currently unsupported.
.Ss \&pshape
Set a special shape for the current paragraph.
This is a Heirloom extension and currently unsupported.
.Ss \&pso
Include output of a shell command.
Ignored because insecure.
.Ss \&ptr
Print the names and positions of all traps.
This is a groff extension and currently ignored.
.Ss \&pvs
Change post-vertical spacing.
This is a groff extension and currently ignored.
.Ss \&rchar
Remove glyph definitions.
Currently unsupported.
.Ss \&rd
Read from standard input.
Currently ignored.
.Ss \&recursionlimit
Set the maximum stack depth for recursive macros.
This is a Heirloom extension and currently ignored.
.Ss \&return
Exit a macro and return to the caller.
Currently unsupported.
.Ss \&rfschar
Remove font-specific fallback glyph definitions.
Currently unsupported.
.Ss \&rhang
Hang characters at right margin.
This is a Heirloom extension and currently ignored.
.Ss \&rj
Justify unfilled text to the right margin.
Currently ignored.
.Ss \&rm
Remove a request, macro or string.
Its syntax is as follows:
.Pp
.D1 Pf \. Cm \&rm Ar name
.Ss \&rn
Rename a request, macro, diversion, or string.
Currently unsupported.
.Ss \&rnn
Rename a number register.
Currently unsupported.
.Ss \&rr
Remove a register.
Its syntax is as follows:
.Pp
.D1 Pf \. Cm \&rr Ar name
.Ss \&rs
End no-space mode.
Currently ignored.
.Ss \&rt
Return to marked vertical position.
Currently ignored.
.Ss \&schar
Define global fallback glyph.
This is a groff extension and currently unsupported.
.Ss \&sentchar
Define sentence-ending characters.
This is a Heirloom extension and currently ignored.
.Ss \&shc
Change the soft hyphen character.
Currently ignored.
.Ss \&shift
Shift macro arguments.
Currently unsupported.
.Ss \&sizes
Define permissible point sizes.
This is a groff extension and currently ignored.
.Ss \&so
Include a source file.
Its syntax is as follows:
.Pp
.D1 Pf \. Cm \&so Ar file
.Pp
The
.Ar file
will be read and its contents processed as input in place of the
.Sq \&.so
request line.
To avoid inadvertent inclusion of unrelated files,
.Xr mandoc 1
only accepts relative paths not containing the strings
.Qq ../
and
.Qq /.. .
.Pp
This request requires
.Xr man 1
to change to the right directory before calling
.Xr mandoc 1 ,
per convention to the root of the manual tree.
Typical usage looks like:
.Pp
.Dl \&.so man3/Xcursor.3
.Pp
As the whole concept is rather fragile, the use of
.Sx \&so
is discouraged.
Use
.Xr ln 1
instead.
.Ss \&spacewidth
Set the space width from the font metrics file.
This is a Heirloom extension and currently ignored.
.Ss \&special
Define a special font.
This is a groff extension and currently ignored.
.Ss \&spreadwarn
Warn about wide spacing between words.
Currently ignored.
.Ss \&ss
Set space character size.
Currently ignored.
.Ss \&sty
Associate style with a font position.
This is a groff extension and currently ignored.
.Ss \&substring
Replace a user-defined string with a substring.
Currently unsupported.
.Ss \&sv
Save vertical space.
Currently ignored.
.Ss \&sy
Execute shell command.
Ignored because insecure.
.Ss \&T&
Re-start a table layout, retaining the options of the prior table
invocation.
See
.Sx \&TS .
.Ss \&ta
Set tab stops.
Takes an arbitrary number of arguments.
Currently unsupported.
.Ss \&tc
Change tab repetion character.
Currently unsupported.
.Ss \&TE
End a table context.
See
.Sx \&TS .
.Ss \&ti
Temporary indent.
Currently unsupported.
.Ss \&tkf
Enable track kerning for a font.
Currently ignored.
.Ss \&tl
Print a title line.
Currently unsupported.
.Ss \&tm
Print to standard error output.
Currently ignored.
.Ss \&tm1
Print to standard error output, allowing leading blanks.
This is a groff extension and currently ignored.
.Ss \&tmc
Print to standard error output without a trailing newline.
This is a groff extension and currently ignored.
.Ss \&tr
Output character translation.
Its syntax is as follows:
.Pp
.D1 Pf \. Cm \&tr Ar [ab]+
.Pp
Pairs of
.Ar ab
characters are replaced
.Ar ( a
for
.Ar b ) .
Replacement (or origin) characters may also be character escapes; thus,
.Pp
.Dl tr \e(xx\e(yy
.Pp
replaces all invocations of \e(xx with \e(yy.
.Ss \&track
Static letter space tracking.
This is a Heirloom extension and currently ignored.
.Ss \&transchar
Define transparent characters for sentence-ending.
This is a Heirloom extension and currently ignored.
.Ss \&trf
Output the contents of a file, disallowing invalid characters.
This is a groff extension and ignored because insecure.
.Ss \&trimat
Set the TrimBox page parameter for PDF generation.
This is a Heirloom extension and currently ignored.
.Ss \&trin
Output character translation, ignored by
.Cm \&asciify .
Currently unsupported.
.Ss \&trnt
Output character translation, ignored by \e!.
Currently unsupported.
.Ss \&troff
Force troff mode.
This is a groff extension and currently ignored.
.Ss \&TS
Begin a table, which formats input in aligned rows and columns.
See
.Xr tbl 7
for a description of the tbl language.
.Ss \&uf
Globally set the underline font.
Currently ignored.
.Ss \&ul
Underline.
Currently ignored.
.Ss \&unformat
Unformat spaces and tabs in a diversion.
Currently unsupported.
.Ss \&unwatch
Disable notification for string or macro.
This is a Heirloom extension and currently ignored.
.Ss \&unwatchn
Disable notification for register.
This is a Heirloom extension and currently ignored.
.Ss \&vpt
Enable or disable vertical position traps.
This is a groff extension and currently ignored.
.Ss \&vs
Change vertical spacing.
Currently ignored.
.Ss \&warn
Set warning level.
Currently ignored.
.Ss \&warnscale
Set the scaling indicator used in warnings.
This is a groff extension and currently ignored.
.Ss \&watch
Notify on change of string or macro.
This is a Heirloom extension and currently ignored.
.Ss \&watchlength
On change, report the contents of macros and strings
up to the sepcified length.
This is a Heirloom extension and currently ignored.
.Ss \&watchn
Notify on change of register.
This is a Heirloom extension and currently ignored.
.Ss \&wh
Set a page location trap.
Currently unsupported.
.Ss \&while
Repeated execution while a condition is true.
Currently unsupported.
.Ss \&write
Write to an open file.
Ignored because insecure.
.Ss \&writec
Write to an open file without appending a newline.
Ignored because insecure.
.Ss \&writem
Write macro or string to an open file.
Ignored because insecure.
.Ss \&xflag
Set the extension level.
This is a Heirloom extension and currently ignored.
.Ss Numerical expressions
The
.Sx \&nr ,
.Sx \&if ,
and
.Sx \&ie
requests accept integer numerical expressions as arguments.
These are always evaluated using the C
.Vt int
type; integer overflow works the same way as in the C language.
Numbers consist of an arbitrary number of digits
.Sq 0
to
.Sq 9
prefixed by an optional sign
.Sq +
or
.Sq - .
Each number may be followed by one optional scaling unit described below
.Sx Scaling Widths .
The following equations hold:
.Bd -literal -offset indent
1i = 6v = 6P = 10m = 10n = 72p = 1000M = 240u = 240
254c = 100i = 24000u = 24000
1f = 65536u = 65536
.Ed
.Pp
The following binary operators are implemented.
Unless otherwise stated, they behave as in the C language:
.Pp
.Bl -tag -width 2n -compact
.It Ic +
addition
.It Ic -
subtraction
.It Ic *
multiplication
.It Ic /
division
.It Ic %
remainder of division
.It Ic <
less than
.It Ic >
greater than
.It Ic ==
equal to
.It Ic =
equal to, same effect as
.Ic ==
(this differs from C)
.It Ic <=
less than or equal to
.It Ic >=
greater than or equal to
.It Ic <>
not equal to (corresponds to C
.Ic != ;
this one is of limited portability, it is supported by Heirloom roff,
but not by groff)
.It Ic &
logical and (corresponds to C
.Ic && )
.It Ic \&:
logical or (corresponds to C
.Ic \&|| )
.It Ic <?
minimum (not available in C)
.It Ic >?
maximum (not available in C)
.El
.Pp
There is no concept of precendence; evaluation proceeds from left to right,
except when subexpressions are enclosed in parantheses.
Inside parentheses, whitespace is ignored.
.Sh ESCAPE SEQUENCE REFERENCE
The
.Xr mandoc 1
.Nm
parser recognises the following escape sequences.
Note that the
.Nm
language defines more escape sequences not implemented in
.Xr mandoc 1 .
In
.Xr mdoc 7
and
.Xr man 7
documents, using escape sequences is discouraged except for those
described in the
.Sx LANGUAGE SYNTAX
section above.
.Pp
A backslash followed by any character not listed here
simply prints that character itself.
.Ss \e<newline>
A backslash at the end of an input line can be used to continue the
logical input line on the next physical input line, joining the text
on both lines together as if it were on a single input line.
.Ss \e<space>
The escape sequence backslash-space
.Pq Sq \e\ \&
is an unpaddable space-sized non-breaking space character; see
.Sx Whitespace .
.Ss \e\(dq
The rest of the input line is treated as
.Sx Comments .
.Ss \e%
Hyphenation allowed at this point of the word; ignored by
.Xr mandoc 1 .
.Ss \e&
Non-printing zero-width character; see
.Sx Whitespace .
.Ss \e\(aq
Acute accent special character; use
.Sq \e(aa
instead.
.Ss \e( Ns Ar cc
.Sx Special Characters
with two-letter names, see
.Xr mandoc_char 7 .
.Ss \e*[ Ns Ar name ]
Interpolate the string with the
.Ar name ;
see
.Sx Predefined Strings
and
.Sx ds .
For short names, there are variants
.No \e* Ns Ar c
and
.No \e*( Ns Ar cc .
.Ss \e-
Special character
.Dq mathematical minus sign .
.Ss \e[ Ns Ar name ]
.Sx Special Characters
with names of arbitrary length, see
.Xr mandoc_char 7 .
.Ss \e^
One-twelfth em half-narrow space character, effectively zero-width in
.Xr mandoc 1 .
.Ss \e`
Grave accent special character; use
.Sq \e(ga
instead.
.Ss \e{
Begin conditional input; see
.Sx if .
.Ss \e\(ba
One-sixth em narrow space character, effectively zero-width in
.Xr mandoc 1 .
.Ss \e}
End conditional input; see
.Sx if .
.Ss \e~
Paddable non-breaking space character.
.Ss \e0
Digit width space character.
.Ss \eA\(aq Ns Ar string Ns \(aq
Anchor definition; ignored by
.Xr mandoc 1 .
.Ss \eB\(aq Ns Ar string Ns \(aq
Interpolate
.Sq 1
if
.Ar string
conforms to the syntax of
.Sx Numerical expressions
explained above and
.Sq 0
otherwise.
.Ss \eb\(aq Ns Ar string Ns \(aq
Bracket building function; ignored by
.Xr mandoc 1 .
.Ss \eC\(aq Ns Ar name Ns \(aq
.Sx Special Characters
with names of arbitrary length.
.Ss \ec
When encountered at the end of an input text line,
the next input text line is considered to continue that line,
even if there are request or macro lines in between.
No whitespace is inserted.
.Ss \eD\(aq Ns Ar string Ns \(aq
Draw graphics function; ignored by
.Xr mandoc 1 .
.Ss \ed
Move down by half a line; ignored by
.Xr mandoc 1 .
.Ss \ee
Backslash special character.
.Ss \eF[ Ns Ar name ]
Switch font family (groff extension); ignored by
.Xr mandoc 1 .
For short names, there are variants
.No \eF Ns Ar c
and
.No \eF( Ns Ar cc .
.Ss \ef[ Ns Ar name ]
Switch to the font
.Ar name ,
see
.Sx Text Decoration .
For short names, there are variants
.No \ef Ns Ar c
and
.No \ef( Ns Ar cc .
.Ss \eg[ Ns Ar name ]
Interpolate the format of a number register; ignored by
.Xr mandoc 1 .
For short names, there are variants
.No \eg Ns Ar c
and
.No \eg( Ns Ar cc .
.Ss \eH\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
Set the height of the current font; ignored by
.Xr mandoc 1 .
.Ss \eh\(aq Ns Ar number Ns \(aq
Horizontal motion; ignored by
.Xr mandoc 1 .
.Ss \ek[ Ns Ar name ]
Mark horizontal input place in register; ignored by
.Xr mandoc 1 .
For short names, there are variants
.No \ek Ns Ar c
and
.No \ek( Ns Ar cc .
.Ss \eL\(aq Ns Ar number Ns Oo Ar c Oc Ns \(aq
Vertical line drawing function; ignored by
.Xr mandoc 1 .
.Ss \el\(aq Ns Ar number Ns Oo Ar c Oc Ns \(aq
Horizontal line drawing function; ignored by
.Xr mandoc 1 .
.Ss \eM[ Ns Ar name ]
Set fill (background) color (groff extension); ignored by
.Xr mandoc 1 .
For short names, there are variants
.No \eM Ns Ar c
and
.No \eM( Ns Ar cc .
.Ss \em[ Ns Ar name ]
Set glyph drawing color (groff extension); ignored by
.Xr mandoc 1 .
For short names, there are variants
.No \em Ns Ar c
and
.No \em( Ns Ar cc .
.Ss \eN\(aq Ns Ar number Ns \(aq
Character
.Ar number
on the current font.
.Ss \en[ Ns Ar name ]
Interpolate the number register
.Ar name .
For short names, there are variants
.No \en Ns Ar c
and
.No \en( Ns Ar cc .
.Ss \eo\(aq Ns Ar string Ns \(aq
Overstrike, writing all the characters contained in the
.Ar string
to the same output position.
In terminal and HTML output modes,
only the last one of the characters is visible.
.Ss \eR\(aq Ns Ar name Oo +|- Oc Ns Ar number Ns \(aq
Set number register; ignored by
.Xr mandoc 1 .
.Ss \eS\(aq Ns Ar number Ns \(aq
Slant output; ignored by
.Xr mandoc 1 .
.Ss \es\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
Change point size; ignored by
.Xr mandoc 1 .
Alternative forms
.No \es Ns Oo +|- Oc Ns Ar n ,
.No \es Ns Oo +|- Oc Ns \(aq Ns Ar number Ns \(aq ,
.No \es Ns [ Oo +|- Oc Ns Ar number ] ,
and
.No \es Ns Oo +|- Oc Ns [ Ar number Ns ]
are also parsed and ignored.
.Ss \et
Horizontal tab; ignored by
.Xr mandoc 1 .
.Ss \eu
Move up by half a line; ignored by
.Xr mandoc 1 .
.Ss \eV[ Ns Ar name ]
Interpolate an environment variable; ignored by
.Xr mandoc 1 .
For short names, there are variants
.No \eV Ns Ar c
and
.No \eV( Ns Ar cc .
.Ss \ev\(aq Ns Ar number Ns \(aq
Vertical motion; ignored by
.Xr mandoc 1 .
.Ss \ew\(aq Ns Ar string Ns \(aq
Interpolate the width of the
.Ar string .
The
.Xr mandoc 1
implementation assumes that after expansion of user-defined strings, the
.Ar string
only contains normal characters, no escape sequences, and that each
character has a width of 24 basic units.
.Ss \eX\(aq Ns Ar string Ns \(aq
Output
.Ar string
as device control function; ignored in nroff mode and by
.Xr mandoc 1 .
.Ss \ex\(aq Ns Ar number Ns \(aq
Extra line space function; ignored by
.Xr mandoc 1 .
.Ss \eY[ Ns Ar name ]
Output a string as a device control function; ignored in nroff mode and by
.Xr mandoc 1 .
For short names, there are variants
.No \eY Ns Ar c
and
.No \eY( Ns Ar cc .
.Ss \eZ\(aq Ns Ar string Ns \(aq
Print
.Ar string
with zero width and height; ignored by
.Xr mandoc 1 .
.Ss \ez
Output the next character without advancing the cursor position.
.Sh COMPATIBILITY
The
.Xr mandoc 1
implementation of the
.Nm
language is intentionally incomplete.
Unimplemented features include:
.Pp
.Bl -dash -compact
.It
For security reasons,
.Xr mandoc 1
never reads or writes external files except via
.Sx \&so
requests with safe relative paths.
.It
There is no automatic hyphenation, no adjustment to the right margin,
and no centering; the output is always set flush-left.
.It
Support for setting tabulator positions
and tabulator and leader characters is missing,
and support for manually changing indentation is limited.
.It
The
.Sq u
scaling unit is the default terminal unit.
In traditional troff systems, this unit changes depending on the
output media.
.It
Width measurements are implemented in a crude way
and often yield wrong results.
Explicit movement requests and escapes are ignored.
.It
There is no concept of output pages, no support for floats,
graphics drawing, and picture inclusion;
terminal output is always continuous.
.It
Requests regarding color, font families, and glyph manipulation
are ignored.
Font support is very limited.
Kerning is not implemented, and no ligatures are produced.
.It
The
.Qq \(aq
macro control character does not suppress output line breaks.
.It
Diversions are not implemented,
and support for traps is very incomplete.
.It
While recursion is supported,
.Sx \&while
loops are not.
.El
.Pp
The special semantics of the
.Cm nS
number register is an idiosyncracy of
.Ox
manuals and not supported by other
.Xr mdoc 7
implementations.
.Sh SEE ALSO
.Xr mandoc 1 ,
.Xr eqn 7 ,
.Xr man 7 ,
.Xr mandoc_char 7 ,
.Xr mdoc 7 ,
.Xr tbl 7
.Rs
.%A Joseph F. Ossanna
.%A Brian W. Kernighan
.%I AT&T Bell Laboratories
.%T Troff User's Manual
.%R Computing Science Technical Report
.%N 54
.%C Murray Hill, New Jersey
.%D 1976 and 1992
.%U http://www.kohala.com/start/troff/cstr54.ps
.Re
.Rs
.%A Joseph F. Ossanna
.%A Brian W. Kernighan
.%A Gunnar Ritter
.%T Heirloom Documentation Tools Nroff/Troff User's Manual
.%D September 17, 2007
.%U http://heirloom.sourceforge.net/doctools/troff.pdf
.Re
.Sh HISTORY
The RUNOFF typesetting system, whose input forms the basis for
.Nm ,
was written in MAD and FAP for the CTSS operating system by Jerome E.
Saltzer in 1964.
Doug McIlroy rewrote it in BCPL in 1969, renaming it
.Nm .
Dennis M. Ritchie rewrote McIlroy's
.Nm
in PDP-11 assembly for
.At v1 ,
Joseph F. Ossanna improved roff and renamed it nroff
for
.At v2 ,
then ported nroff to C as troff, which Brian W. Kernighan released with
.At v7 .
In 1989, James Clarke re-implemented troff in C++, naming it groff.
.Sh AUTHORS
.An -nosplit
This
.Nm
reference was written by
.An Kristaps Dzonsons Aq Mt kristaps@bsd.lv
and
.An Ingo Schwarze Aq Mt schwarze@openbsd.org .