path: root/roff.7

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.\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
.\" Copyright (c) 2010-2018 Ingo Schwarze <schwarze@openbsd.org>
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.Dd $Mdocdate$
.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
and
.Sx Special Characters .
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 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 space 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.
.Bl -tag -width Ds
.It Ic \&ab Op Ar message
Abort processing.
Currently unsupported.
.It Ic \&ad Op Cm b | c | l | n | r
Set line adjustment mode for subsequent text.
Currently ignored.
.It Ic \&af Ar registername format
Assign an output format to a number register.
Currently ignored.
.It Ic \&aln Ar newname oldname
Create an alias for a number register.
Currently unsupported.
.It Ic \&als Ar newname oldname
Create an alias for a request, string, macro, or diversion.
.It Ic \&am Ar macroname Op Ar endmacro
Append to a macro definition.
The syntax of this request is the same as that of
.Ic \&de .
.It Ic \&am1 Ar macroname Op Ar endmacro
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
.Ic \&de1 .
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Ic \&am .
.It Ic \&ami Ar macrostring Op Ar endstring
Append to a macro definition, specifying the macro name indirectly
(groff extension).
The syntax of this request is the same as that of
.Ic \&dei .
.It Ic \&ami1 Ar macrostring Op Ar endstring
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
.Ic \&dei1 .
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Ic \&ami .
.It Ic \&as Ar stringname Op Ar string
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.
.It Ic \&as1 Ar stringname Op Ar string
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
.Ic \&ds1 .
Since
.Xr mandoc 1
does not implement
.Nm
compatibility mode at all, it handles this request as an alias for
.Ic \&as .
.It Ic \&asciify Ar divname
Fully unformat a diversion.
Currently unsupported.
.It Ic \&backtrace
Print a backtrace of the input stack.
This is a groff extension and currently ignored.
.It Ic \&bd Ar font Oo Ar curfont Oc Op Ar offset
Artificially embolden by repeated printing with small shifts.
Currently ignored.
.It Ic \&bleedat Ar left top width height
Set the BleedBox page parameter for PDF generation.
This is a Heirloom extension and currently ignored.
.It Ic \&blm Ar macroname
Set a blank line trap.
Currently unsupported.
.It Ic \&box Ar divname
Begin a diversion without including a partially filled line.
Currently unsupported.
.It Ic \&boxa Ar divname
Add to a diversion without including a partially filled line.
Currently unsupported.
.It Ic \&bp Oo Cm + Ns | Ns Cm - Oc Ns Ar pagenumber
Begin a new page.
Currently ignored.
.It Ic \&BP Ar source height width position offset flags label
Define a frame and place a picture in it.
This is a Heirloom extension and currently unsupported.
.It Ic \&br
Break the output line.
.It Ic \&break
Break out of a
.Ic \&while
loop.
Currently unsupported.
.It Ic \&breakchar Ar char ...
Optional line break characters.
This is a Heirloom extension and currently ignored.
.It Ic \&brnl Ar N
Break output line after the next
.Ar N
input lines.
This is a Heirloom extension and currently ignored.
.It Ic \&brp
Break and spread output line.
Currently, this is implemented as an alias for
.Ic \&br .
.It Ic \&brpnl Ar N
Break and spread output line after the next
.Ar N
input lines.
This is a Heirloom extension and currently ignored.
.It Ic \&c2 Op Ar char
Change the no-break control character.
Currently unsupported.
.It Ic \&cc Op Ar char
Change the control character.
If
.Ar char
is not specified, the control character is reset to
.Sq \&. .
Trailing characters are ignored.
.It Ic \&ce Op Ar N
Center the next
.Ar N
input lines without filling.
.Ar N
defaults to 1.
An argument of 0 or less ends centering.
Currently, high level macros abort centering.
.It Ic \&cf Ar filename
Output the contents of a file.
Ignored because insecure.
.It Ic \&cflags Ar flags char ...
Set character flags.
This is a groff extension and currently ignored.
.It Ic \&ch Ar macroname Op Ar dist
Change a trap location.
Currently ignored.
.It Ic \&char Ar glyphname Op Ar string
Define a new glyph.
Currently unsupported.
.It Ic \&chop Ar stringname
Remove the last character from a macro, string, or diversion.
Currently unsupported.
.It Ic \&class Ar classname char ...
Define a character class.
This is a groff extension and currently ignored.
.It Ic \&close Ar streamname
Close an open file.
Ignored because insecure.
.It Ic \&CL Ar color text
Print text in color.
This is a Heirloom extension and currently unsupported.
.It Ic \&color Op Cm 1 | 0
Activate or deactivate colors.
This is a groff extension and currently ignored.
.It Ic \&composite Ar from to
Define a name component for composite glyph names.
This is a groff extension and currently unsupported.
.It Ic \&continue
Immediately start the next iteration of a
.Ic \&while
loop.
Currently unsupported.
.It Ic \&cp Op Cm 1 | 0
Switch
.Nm
compatibility mode on or off.
Currently ignored.
.It Ic \&cropat Ar left top width height
Set the CropBox page parameter for PDF generation.
This is a Heirloom extension and currently ignored.
.It Ic \&cs Ar font Op Ar width Op Ar emsize
Constant character spacing mode.
Currently ignored.
.It Ic \&cu Op Ar N
Underline next
.Ar N
input lines including whitespace.
Currently ignored.
.It Ic \&da Ar divname
Append to a diversion.
Currently unsupported.
.It Ic \&dch Ar macroname Op Ar dist
Change a trap location in the current diversion.
This is a Heirloom extension and currently unsupported.
.It Ic \&de Ar macroname Op Ar endmacro
Define a
.Nm
macro.
Its syntax can be either
.Bd -literal -offset indent
.Pf . Ic \&de Ar macroname
.Ar definition
\&..
.Ed
.Pp
or
.Bd -literal -offset indent
.Pf . Ic \&de Ar macroname Ar endmacro
.Ar definition
.Pf . Ar endmacro
.Ed
.Pp
Both forms define or redefine the macro
.Ar macroname
to represent the
.Ar 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 endmacro
macro works in the same way as for
.Ic \&ig ;
namely, the call to
.Sq Pf . Ar endmacro
first ends the
.Ar 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 macroname 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 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$2
\&..
\&.ZN XtFree .
.Ed
.Pp
produces
.Pp
.D1 \efI\e^XtFree\e^\efP.
.Pp
in the input stream, and thus in the output: \fI\^XtFree\^\fP.
Each occurrence of \e\e$* is replaced with all the arguments,
joined together with single space characters.
.Pp
Since macros and user-defined strings share a common string table,
defining a macro
.Ar macroname
clobbers the user-defined string
.Ar macroname ,
and the
.Ar definition
can also be printed using the
.Sq \e*
string interpolation syntax described below
.Ic 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.
.It Ic \&de1 Ar macroname Op Ar endmacro
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
.Ic \&de .
.It Ic \&defcolor Ar newname scheme component ...
Define a color name.
This is a groff extension and currently ignored.
.It Ic \&dei Ar macrostring Op Ar endstring
Define a
.Nm
macro, specifying the macro name indirectly (groff extension).
The syntax of this request is the same as that of
.Ic \&de .
The effect is the same as:
.Pp
.D1 Pf . Cm \&de No \e* Ns Bo Ar macrostring Bc Op \e* Ns Bq Ar endstring
.It Ic \&dei1 Ar macrostring Op Ar endstring
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
.Ic \&dei .
.It Ic \&device Ar string ...
.It Ic \&devicem Ar stringname
These two requests only make sense with the groff-specific intermediate
output format and are unsupported.
.It Ic \&di Ar divname
Begin a diversion.
Currently unsupported.
.It Ic \&do Ar command Op Ar argument ...
Execute
.Nm
request or macro line with compatibility mode disabled.
Currently unsupported.
.It Ic \&ds Ar stringname Op Oo \(dq Oc Ns Ar string
Define a user-defined string.
The
.Ar stringname
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 stringname
for a
.Ar stringname
of arbitrary length, or \e*(NN or \e*N if the length of
.Ar stringname
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 stringname
clobbers the macro
.Ar stringname ,
and the
.Ar stringname
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
.Ic SH
macro when used in a
.Xr man 7
document.
Such abuse is of course strongly discouraged.
.It Ic \&ds1 Ar stringname Op Oo \(dq Oc Ns Ar string
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
.Ic \&ds .
.It Ic \&dwh Ar dist macroname
Set a location trap in the current diversion.
This is a Heirloom extension and currently unsupported.
.It Ic \&dt Op Ar dist macroname
Set a trap within a diversion.
Currently unsupported.
.It Ic \&ec Op Ar char
Enable the escape mechanism and change the escape character.
The
.Ar char
argument defaults to the backslash
.Pq Sq \e .
.It Ic \&ecr
Restore the escape character.
Currently unsupported.
.It Ic \&ecs
Save the escape character.
Currently unsupported.
.It Ic \&el Ar body
The
.Dq else
half of an if/else conditional.
Pops a result off the stack of conditional evaluations pushed by
.Ic \&ie
and uses it as its conditional.
If no stack entries are present (e.g., due to no prior
.Ic \&ie
calls)
then false is assumed.
The syntax of this request is similar to
.Ic \&if
except that the conditional is missing.
.It Ic \&em Ar macroname
Set a trap at the end of input.
Currently unsupported.
.It Ic \&EN
End an equation block.
See
.Ic \&EQ .
.It Ic \&eo
Disable the escape mechanism completely.
.It Ic \&EP
End a picture started by
.Ic \&BP .
This is a Heirloom extension and currently unsupported.
.It Ic \&EQ
Begin an equation block.
See
.Xr eqn 7
for a description of the equation language.
.It Ic \&errprint Ar message
Print a string like an error message.
This is a Heirloom extension and currently ignored.
.It Ic \&ev Op Ar envname
Switch to another environment.
Currently unsupported.
.It Ic \&evc Op Ar envname
Copy an environment into the current environment.
Currently unsupported.
.It Ic \&ex
Abort processing and exit.
Currently unsupported.
.It Ic \&fallback Ar curfont font ...
Select the fallback sequence for a font.
This is a Heirloom extension and currently ignored.
.It Ic \&fam Op Ar familyname
Change the font family.
This is a groff extension and currently ignored.
.It Ic \&fc Op Ar delimchar Op Ar padchar
Define a delimiting and a padding character for fields.
Currently unsupported.
.It Ic \&fchar Ar glyphname Op Ar string
Define a fallback glyph.
Currently unsupported.
.It Ic \&fcolor Ar colorname
Set the fill color for \eD objects.
This is a groff extension and currently ignored.
.It Ic \&fdeferlig Ar font string ...
Defer ligature building.
This is a Heirloom extension and currently ignored.
.It Ic \&feature Cm + Ns | Ns Cm - Ns Ar name
Enable or disable an OpenType feature.
This is a Heirloom extension and currently ignored.
.It Ic \&fi
Switch to fill mode.
See
.Xr man 7 .
Ignored in
.Xr mdoc 7 .
.It Ic \&fkern Ar font minkern
Control the use of kerning tables for a font.
This is a Heirloom extension and currently ignored.
.It Ic \&fl
Flush output.
Currently ignored.
.It Ic \&flig Ar font string char ...
Define ligatures.
This is a Heirloom extension and currently ignored.
.It Ic \&fp Ar position font Op Ar filename
Assign font position.
Currently ignored.
.It Ic \&fps Ar mapname ...
Mount a font with a special character map.
This is a Heirloom extension and currently ignored.
.It Ic \&fschar Ar font glyphname Op Ar string
Define a font-specific fallback glyph.
This is a groff extension and currently unsupported.
.It Ic \&fspacewidth Ar font Op Ar afmunits
Set a font-specific width for the space character.
This is a Heirloom extension and currently ignored.
.It Ic \&fspecial Ar curfont Op Ar font ...
Conditionally define a special font.
This is a groff extension and currently ignored.
.It Ic \&ft Op Ar font
Change the font.
The following
.Ar font
arguments are supported:
.Bl -tag -width 4n -offset indent
.It Cm B , BI , CB , 3 , 4
switches to
.Sy bold
font
.It Cm I , CI , 2
switches to
.Em underlined
font
.It Cm R , CR , 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 and may be overridden
by macros and escape sequences.
.It Ic \&ftr Ar newname Op Ar oldname
Translate font name.
This is a groff extension and currently ignored.
.It Ic \&fzoom Ar font Op Ar permille
Zoom font size.
Currently ignored.
.It Ic \&gcolor Op Ar colorname
Set glyph color.
This is a groff extension and currently ignored.
.It Ic \&hc Op Ar char
Set the hyphenation character.
Currently ignored.
.It Ic \&hcode Ar char code ...
Set hyphenation codes of characters.
Currently ignored.
.It Ic \&hidechar Ar font char ...
Hide characters in a font.
This is a Heirloom extension and currently ignored.
.It Ic \&hla Ar language
Set hyphenation language.
This is a groff extension and currently ignored.
.It Ic \&hlm Op Ar number
Set maximum number of consecutive hyphenated lines.
Currently ignored.
.It Ic \&hpf Ar filename
Load hyphenation pattern file.
This is a groff extension and currently ignored.
.It Ic \&hpfa Ar filename
Load hyphenation pattern file, appending to the current patterns.
This is a groff extension and currently ignored.
.It Ic \&hpfcode Ar code code ...
Define mapping values for character codes in hyphenation patterns.
This is a groff extension and currently ignored.
.It Ic \&hw Ar word ...
Specify hyphenation points in words.
Currently ignored.
.It Ic \&hy Op Ar mode
Set automatic hyphenation mode.
Currently ignored.
.It Ic \&hylang Ar language
Set hyphenation language.
This is a Heirloom extension and currently ignored.
.It Ic \&hylen Ar nchar
Minimum word length for hyphenation.
This is a Heirloom extension and currently ignored.
.It Ic \&hym Op Ar length
Set hyphenation margin.
This is a groff extension and currently ignored.
.It Ic \&hypp Ar penalty ...
Define hyphenation penalties.
This is a Heirloom extension and currently ignored.
.It Ic \&hys Op Ar length
Set hyphenation space.
This is a groff extension and currently ignored.
.It Ic \&ie Ar condition body
The
.Dq if
half of an if/else conditional.
The result of the conditional is pushed into a stack used by subsequent
invocations of
.Ic \&el ,
which may be separated by any intervening input (or not exist at all).
Its syntax is equivalent to
.Ic \&if .
.It Ic \&if Ar condition body
Begin a conditional.
This request can also be written as follows:
.Bd -unfilled -offset indent
.Pf . Ic \&if Ar condition No \e{ Ns Ar body
.Ar body ... Ns \e}
.Ed
.Bd -unfilled -offset indent
.Pf . Ic \&if Ar condition No \e{\e
.Ar body ...
.Pf . No \e}
.Ed
.Pp
The
.Ar condition
is a boolean expression.
Currently,
.Xr mandoc 1
supports the following subset of roff conditionals:
.Bl -bullet
.It
If
.Sq \&!
is prefixed to
.Ar condition ,
it is logically inverted.
.It
If the first character of
.Ar condition
is
.Sq n
.Pq nroff mode
or
.Sq o
.Pq odd page ,
it evaluates to true, and the
.Ar body
starts with the next character.
.It
If the first character of
.Ar condition
is
.Sq e
.Pq even page ,
.Sq t
.Pq troff mode ,
or
.Sq v
.Pq vroff mode ,
it evaluates to false, and the
.Ar body
starts with the next character.
.It
If the first character of
.Ar condition
is
.Sq c
.Pq character available ,
it evaluates to true if the following character is an ASCII character
or a valid character escape sequence, or to false otherwise.
The
.Ar body
starts with the character following that next character.
.It
If the first character of
.Ar condition
is
.Sq d ,
it evaluates to true if the rest of
.Ar condition
is the name of an existing user defined macro or string;
otherwise, it evaluates to false.
.It
If the first character of
.Ar condition
is
.Sq r ,
it evaluates to true if the rest of
.Ar condition
is the name of an existing number register;
otherwise, it evaluates to false.
.It
If the
.Ar condition
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
.Ar condition
is regarded as a delimiter and it 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
.Ar condition
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
.Ar 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
.Ar body
is not enclosed in braces, scope continues until the end of the line.
If the
.Ar condition
is followed by a
.Ar 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 -unfilled -offset indent
.Pf . Ic \&if Ar condition No \e{\e
.Pf . Ar request
.Pf . No \e}
.Ed
.Pp
than having the request or macro follow as
.Pp
.D1 Pf . Ic \&if Ar condition Pf \e{. Ar request
.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.
.It Ic \&ig Op Ar endmacro
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 endmacro
.Ar ignored text
.Pf . Ar endmacro
.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 endmacro
is encountered.
Do not use the escape character
.Sq \e
anywhere in the definition of
.Ar endmacro ;
it would cause very strange behaviour.
.Pp
When the
.Ar endmacro
is a roff request or a roff macro, like in
.Pp
.D1 \&.ig if
.Pp
the subsequent invocation of
.Ic \&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.
.It Ic \&in Op Oo Cm + Ns | Ns Cm - Oc Ns Ar width
Change indentation.
See
.Xr man 7 .
Ignored in
.Xr mdoc 7 .
.It Ic \&index Ar register stringname substring
Find a substring in a string.
This is a Heirloom extension and currently unsupported.
.It Ic \&it Ar expression macro
Set an input line trap.
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.
.It Ic \&it Ar expression macro
Set an input line trap, not counting lines ending with \ec.
Currently unsupported.
.It Ic \&IX Ar class keystring
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.
.It Ic \&kern Op Cm 1 | 0
Switch kerning on or off.
Currently ignored.
.It Ic \&kernafter Ar font char ... afmunits ...
Increase kerning after some characters.
This is a Heirloom extension and currently ignored.
.It Ic \&kernbefore Ar font char ... afmunits ...
Increase kerning before some characters.
This is a Heirloom extension and currently ignored.
.It Ic \&kernpair Ar font char ... font char ... afmunits
Add a kerning pair to the kerning table.
This is a Heirloom extension and currently ignored.
.It Ic \&lc Op Ar glyph
Define a leader repetition character.
Currently unsupported.
.It Ic \&lc_ctype Ar localename
Set the
.Dv LC_CTYPE
locale.
This is a Heirloom extension and currently unsupported.
.It Ic \&lds Ar macroname string
Define a local string.
This is a Heirloom extension and currently unsupported.
.It Ic \&length Ar register string
Count the number of input characters in a string.
Currently unsupported.
.It Ic \&letadj Ar lspmin lshmin letss lspmax lshmax
Dynamic letter spacing and reshaping.
This is a Heirloom extension and currently ignored.
.It Ic \&lf Ar lineno Op Ar filename
Change the line number for error messages.
Ignored because insecure.
.It Ic \&lg Op Cm 1 | 0
Switch the ligature mechanism on or off.
Currently ignored.
.It Ic \&lhang Ar font char ... afmunits
Hang characters at left margin.
This is a Heirloom extension and currently ignored.
.It Ic \&linetabs Op Cm 1 | 0
Enable or disable line-tabs mode.
This is a groff extension and currently unsupported.
.It Ic \&ll Op Oo Cm + Ns | Ns Cm - Oc Ns Ar width
Change the output line length.
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.
.It Ic \&lnr Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar value Op Ar increment
Set local number register.
This is a Heirloom extension and currently unsupported.
.It Ic \&lnrf Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar value Op Ar increment
Set local floating-point register.
This is a Heirloom extension and currently unsupported.
.It Ic \&lpfx Ar string
Set a line prefix.
This is a Heirloom extension and currently unsupported.
.It Ic \&ls Op Ar factor
Set line spacing.
It takes one integer argument specifying the vertical distance of
subsequent output text lines measured in v units.
Currently ignored.
.It Ic \&lsm Ar macroname
Set a leading spaces trap.
This is a groff extension and currently unsupported.
.It Ic \&lt Op Oo Cm + Ns | Ns Cm - Oc Ns Ar width
Set title line length.
Currently ignored.
.It Ic \&mc Ar glyph Op Ar dist
Print margin character in the right margin.
The
.Ar dist
is currently ignored; instead, 1n is used.
.It Ic \&mediasize Ar media
Set the device media size.
This is a Heirloom extension and currently ignored.
.It Ic \&minss Ar width
Set minimum word space.
This is a Heirloom extension and currently ignored.
.It Ic \&mk Op Ar register
Mark vertical position.
Currently ignored.
.It Ic \&mso Ar filename
Load a macro file using the search path.
Ignored because insecure.
.It Ic \&na
Disable adjusting without changing the adjustment mode.
Currently ignored.
.It Ic \&ne Op Ar height
Declare the need for the specified minimum vertical space
before the next trap or the bottom of the page.
Currently ignored.
.It Ic \&nf
Switch to no-fill mode.
See
.Xr man 7 .
Ignored by
.Xr mdoc 7 .
.It Ic \&nh
Turn off automatic hyphenation mode.
Currently ignored.
.It Ic \&nhychar Ar char ...
Define hyphenation-inhibiting characters.
This is a Heirloom extension and currently ignored.
.It Ic \&nm Op Ar start Op Ar inc Op Ar space Op Ar indent
Print line numbers.
Currently unsupported.
.It Ic \&nn Op Ar number
Temporarily turn off line numbering.
Currently unsupported.
.It Ic \&nop Ar body
Execute the rest of the input line as a request, macro, or text line,
skipping the
.Ic \&nop
request and any space characters immediately following it.
This is mostly used to indent text lines inside macro definitions.
.It Ic \&nr Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar expression Op Ar stepsize
Define or change a register.
A register is an arbitrary string value that defines some sort of state,
which influences parsing and/or formatting.
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
.Ar stepsize
is used by the
.Ic \en+
auto-increment feature.
It remains unchanged when omitted while changing an existing register,
and it defaults to 0 when defining a new register.
.Pp
The following
.Ar register
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
.Ic \&Sh
macro will reset this register.
.El
.It Xo
.Ic \&nrf Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar expression
.Op Ar increment
.Xc
Define or change a floating-point register.
This is a Heirloom extension and currently unsupported.
.It Ic \&nroff
Force nroff mode.
This is a groff extension and currently ignored.
.It Ic \&ns
Turn on no-space mode.
Currently ignored.
.It Ic \&nx Op Ar filename
Abort processing of the current input file and process another one.
Ignored because insecure.
.It Ic \&open Ar stream file
Open a file for writing.
Ignored because insecure.
.It Ic \&opena Ar stream file
Open a file for appending.
Ignored because insecure.
.It Ic \&os
Output saved vertical space.
Currently ignored.
.It Ic \&output Ar string
Output directly to intermediate output.
Not supported.
.It Ic \&padj Op Cm 1 | 0
Globally control paragraph-at-once adjustment.
This is a Heirloom extension and currently ignored.
.It Ic \&papersize Ar media
Set the paper size.
This is a Heirloom extension and currently ignored.
.It Ic \&pc Op Ar char
Change the page number character.
Currently ignored.
.It Ic \&pev
Print environments.
This is a groff extension and currently ignored.
.It Ic \&pi Ar command
Pipe output to a shell command.
Ignored because insecure.
.It Ic \&PI
Low-level request used by
.Ic \&BP .
This is a Heirloom extension and currently unsupported.
.It Ic \&pl Op Oo Cm + Ns | Ns Cm - Oc Ns Ar height
Change page length.
Currently ignored.
.It Ic \&pm
Print names and sizes of macros, strings, and diversions
to standard error output.
Currently ignored.
.It Ic \&pn Oo Cm + Ns | Ns Cm - Oc Ns Ar number
Change the page number of the next page.
Currently ignored.
.It Ic \&pnr
Print all number registers on standard error output.
Currently ignored.
.It Ic \&po Op Oo Cm + Ns | Ns Cm - Oc Ns Ar offset
Set a horizontal page offset.
If no argument is specified, the page offset is reverted to its
previous value.
If a sign is specified, the new page offset is calculated relative
to the current one; otherwise, it is absolute.
The argument follows the syntax of
.Sx Scaling Widths
and the default scaling unit is
.Cm m .
.It Ic \&ps Op Oo Cm + Ns | Ns Cm - Oc Ns size
Change point size.
Currently ignored.
.It Ic \&psbb Ar filename
Retrieve the bounding box of a PostScript file.
Currently unsupported.
.It Ic \&pshape Ar indent length ...
Set a special shape for the current paragraph.
This is a Heirloom extension and currently unsupported.
.It Ic \&pso Ar command
Include output of a shell command.
Ignored because insecure.
.It Ic \&ptr
Print the names and positions of all traps on standard error output.
This is a groff extension and currently ignored.
.It Ic \&pvs Op Oo Cm + Ns | Ns Cm - Oc Ns Ar height
Change post-vertical spacing.
This is a groff extension and currently ignored.
.It Ic \&rchar Ar glyph ...
Remove glyph definitions.
Currently unsupported.
.It Ic \&rd Op Ar prompt Op Ar argument ...
Read from standard input.
Currently ignored.
.It Ic \&recursionlimit Ar maxrec maxtail
Set the maximum stack depth for recursive macros.
This is a Heirloom extension and currently ignored.
.It Ic \&return Op Ar twice
Exit a macro and return to the caller.
Currently unsupported.
.It Ic \&rfschar Ar font glyph ...
Remove font-specific fallback glyph definitions.
Currently unsupported.
.It Ic \&rhang Ar font char ... afmunits
Hang characters at right margin.
This is a Heirloom extension and currently ignored.
.It Ic \&rj Op Ar N
Justify the next
.Ar N
input lines to the right margin without filling.
.Ar N
defaults to 1.
An argument of 0 or less ends right adjustment.
.It Ic \&rm Ar macroname
Remove a request, macro or string.
.It Ic \&rn Ar oldname newname
Rename a request, macro, diversion, or string.
In
.Xr mandoc 1 ,
user-defined macros,
.Xr mdoc 7
and
.Xr man 7
macros, and user-defined strings can be renamed, but renaming of
predefined strings and of
.Nm
requests is not supported, and diversions are not implemented at all.
.It Ic \&rnn Ar oldname newname
Rename a number register.
Currently unsupported.
.It Ic \&rr Ar register
Remove a register.
.It Ic \&rs
End no-space mode.
Currently ignored.
.It Ic \&rt Op Ar dist
Return to marked vertical position.
Currently ignored.
.It Ic \&schar Ar glyph Op Ar string
Define global fallback glyph.
This is a groff extension and currently unsupported.
.It Ic \&sentchar Ar char ...
Define sentence-ending characters.
This is a Heirloom extension and currently ignored.
.It Ic \&shc Op Ar glyph
Change the soft hyphen character.
Currently ignored.
.It Ic \&shift Op Ar number
Shift macro arguments.
Currently unsupported.
.It Ic \&sizes Ar size ...
Define permissible point sizes.
This is a groff extension and currently ignored.
.It Ic \&so Ar filename
Include a source file.
The file is read and its contents processed as input in place of the
.Ic \&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
.Ic \&so
is discouraged.
Use
.Xr ln 1
instead.
.It Ic \&sp Op Ar height
Break the output line and emit vertical space.
The argument follows the syntax of
.Sx Scaling Widths
and defaults to one blank line
.Pq Li 1v .
.It Ic \&spacewidth Op Cm 1 | 0
Set the space width from the font metrics file.
This is a Heirloom extension and currently ignored.
.It Ic \&special Op Ar font ...
Define a special font.
This is a groff extension and currently ignored.
.It Ic \&spreadwarn Op Ar width
Warn about wide spacing between words.
Currently ignored.
.It Ic \&ss Ar wordspace Op Ar sentencespace
Set space character size.
Currently ignored.
.It Ic \&sty Ar position style
Associate style with a font position.
This is a groff extension and currently ignored.
.It Ic \&substring Ar stringname startpos Op Ar endpos
Replace a user-defined string with a substring.
Currently unsupported.
.It Ic \&sv Op Ar height
Save vertical space.
Currently ignored.
.It Ic \&sy Ar command
Execute shell command.
Ignored because insecure.
.It Ic \&T&
Re-start a table layout, retaining the options of the prior table
invocation.
See
.Sx \&TS .
.It Ic \&ta Op Ar width ... Op Cm T Ar width ...
Set tab stops.
Each
.Ar width
argument follows the syntax of
.Sx Scaling Widths .
If prefixed by a plus sign, it is relative to the previous tab stop.
The arguments after the
.Cm T
marker are used repeatedly as often as needed; for each reuse,
they are taken relative to the last previously established tab stop.
When
.Ic \&ta
is called without arguments, all tab stops are cleared.
.It Ic \&tc Op Ar glyph
Change tab repetition character.
Currently unsupported.
.It Ic \&TE
End a table context.
See
.Sx \&TS .
.It Ic \&ti Oo Cm + Ns | Ns Cm - Oc Ns Ar width
Break the output line and indent the next output line by
.Ar width .
If a sign is specified, the temporary indentation is calculated
relative to the current indentation; otherwise, it is absolute.
The argument follows the syntax of
.Sx Scaling Widths
and the default scaling unit is
.Cm m .
.It Ic \&tkf Ar font minps width1 maxps width2
Enable track kerning for a font.
Currently ignored.
.It Ic \&tl No \& Ap Ar left Ap Ar center Ap Ar right Ap
Print a title line.
Currently unsupported.
.It Ic \&tm Ar string
Print to standard error output.
Currently ignored.
.It Ic \&tm1 Ar string
Print to standard error output, allowing leading blanks.
This is a groff extension and currently ignored.
.It Ic \&tmc Ar string
Print to standard error output without a trailing newline.
This is a groff extension and currently ignored.
.It Ic \&tr Ar glyph glyph ...
Output character translation.
The first glyph in each pair is replaced by the second one.
Character escapes can be used; for example,
.Pp
.Dl tr \e(xx\e(yy
.Pp
replaces all invocations of \e(xx with \e(yy.
.It Ic \&track Ar font minps width1 maxps width2
Static letter space tracking.
This is a Heirloom extension and currently ignored.
.It Ic \&transchar Ar char ...
Define transparent characters for sentence-ending.
This is a Heirloom extension and currently ignored.
.It Ic \&trf Ar filename
Output the contents of a file, disallowing invalid characters.
This is a groff extension and ignored because insecure.
.It Ic \&trimat Ar left top width height
Set the TrimBox page parameter for PDF generation.
This is a Heirloom extension and currently ignored.
.It Ic \&trin Ar glyph glyph ...
Output character translation, ignored by
.Ic \&asciify .
Currently unsupported.
.It Ic \&trnt Ar glyph glyph ...
Output character translation, ignored by \e!.
Currently unsupported.
.It Ic \&troff
Force troff mode.
This is a groff extension and currently ignored.
.It Ic \&TS
Begin a table, which formats input in aligned rows and columns.
See
.Xr tbl 7
for a description of the tbl language.
.It Ic \&uf Ar font
Globally set the underline font.
Currently ignored.
.It Ic \&ul Op Ar N
Underline next
.Ar N
input lines.
Currently ignored.
.It Ic \&unformat Ar divname
Unformat spaces and tabs in a diversion.
Currently unsupported.
.It Ic \&unwatch Ar macroname
Disable notification for string or macro.
This is a Heirloom extension and currently ignored.
.It Ic \&unwatchn Ar register
Disable notification for register.
This is a Heirloom extension and currently ignored.
.It Ic \&vpt Op Cm 1 | 0
Enable or disable vertical position traps.
This is a groff extension and currently ignored.
.It Ic \&vs Op Oo Cm + Ns | Ns Cm - Oc Ns Ar height
Change vertical spacing.
Currently ignored.
.It Ic \&warn Ar flags
Set warning level.
Currently ignored.
.It Ic \&warnscale Ar si
Set the scaling indicator used in warnings.
This is a groff extension and currently ignored.
.It Ic \&watch Ar macroname
Notify on change of string or macro.
This is a Heirloom extension and currently ignored.
.It Ic \&watchlength Ar maxlength
On change, report the contents of macros and strings
up to the specified length.
This is a Heirloom extension and currently ignored.
.It Ic \&watchn Ar register
Notify on change of register.
This is a Heirloom extension and currently ignored.
.It Ic \&wh Ar dist Op Ar macroname
Set a page location trap.
Currently unsupported.
.It Ic \&while Ar condition body
Repeated execution while a condition is true.
Currently unsupported.
.It Ic \&write Oo \(dq Oc Ns Ar string
Write to an open file.
Ignored because insecure.
.It Ic \&writec Oo \(dq Oc Ns Ar string
Write to an open file without appending a newline.
Ignored because insecure.
.It Ic \&writem Ar macroname
Write macro or string to an open file.
Ignored because insecure.
.It Ic \&xflag Ar level
Set the extension level.
This is a Heirloom extension and currently ignored.
.El
.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 precedence; evaluation proceeds from left to right,
except when subexpressions are enclosed in parentheses.
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#
Line continuation with comment.
Discard the rest of the physical input line and 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.
This is a groff extension.
.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 Bq Ar name
Interpolate the string with the
.Ar name .
For short names, there are variants
.No \e* Ns Ar c
and
.No \e*( Ns Ar cc .
.Pp
One string is predefined on the
.Nm
language level: \e*(.T expands to the name of the output device,
for example ascii, utf8, ps, pdf, html, or markdown.
.Pp
Macro sets traditionally predefine additional strings which are not
portable and differ across implementations.
Those supported by
.Xr mandoc 1
are listed in
.Xr mandoc_char 7 .
.Pp
Strings can be defined, changed, and deleted with the
.Ic \&ds ,
.Ic \&as ,
and
.Ic \&rm
requests.
.Ss \e,
Left italic correction (groff extension); ignored by
.Xr mandoc 1 .
.Ss \e-
Special character
.Dq mathematical minus sign .
.Ss \e/
Right italic correction (groff extension); ignored by
.Xr mandoc 1 .
.Ss \e Ns Bq 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 Bq 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 Bq 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 Bq 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 Oo Cm \&| Oc Ns Ar width Ns \(aq
Horizontal motion.
If the vertical bar is given, the motion is relative to the current
indentation.
Otherwise, it is relative to the current position.
The default scaling unit is
.Cm m .
.Ss \ek Ns Bq 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 width Ns Oo Ar c Oc Ns \(aq
Draw a horizontal line of
.Ar width
using the glyph
.Ar c .
.Ss \eM Ns Bq 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 Bq 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 Oo +|- Oc Ns Bq 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 .
If the optional sign is specified,
the register is first incremented or decremented by the
.Ar stepsize
that was specified in the relevant
.Ic \&nr
request, and the changed value is interpolated.
.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 \ep
Break the output line at the end of the current word.
.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 Bq Oo +|- Oc Ns Ar number ,
and
.No \es Ns Oo +|- Oc Ns Bq Ar number
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 Bq 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 Bq 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 .