Decide whether to use_pager as early as possible,

[mandoc.git] / roff.7

diff --git a/roff.7 b/roff.7
index de7b405007eaf76140405529a55391b7c1856d70..114f63eddd20dc096e3e077f1ccc34b08e47ebb6 100644 (file)
--- a/roff.7
+++ b/roff.7
@@ -1,7 +1,7 @@
-.\"    $Id: roff.7,v 1.47 2014/02/14 23:50:57 schwarze Exp $
+.\"    $Id: roff.7,v 1.75 2015/09/24 18:41:22 schwarze Exp $

 .\"
 .\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
 .\"
 .\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>

-.\" Copyright (c) 2010, 2011, 2013, 2014 Ingo Schwarze <schwarze@openbsd.org>
+.\" Copyright (c) 2010, 2011, 2013-2015 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
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above


@@ -15,7 +15,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"

-.Dd $Mdocdate: February 14 2014 $
+.Dd $Mdocdate: September 24 2015 $

 .Dt ROFF 7
 .Os
 .Sh NAME
 .Dt ROFF 7
 .Os
 .Sh NAME


@@ -239,8 +239,9 @@ pica (~1/6 inch)
 .It p
 point (~1/72 inch)
 .It f
 .It p
 point (~1/72 inch)
 .It f

-synonym for
+scale

 .Sq u
 .Sq u

+by 65536

 .It v
 default vertical span
 .It m
 .It v
 default vertical span
 .It m


@@ -254,7 +255,7 @@ width of rendered
 .Pq en
 character
 .It u
 .Pq en
 character
 .It u

-default horizontal span
+default horizontal span for the terminal

 .It M
 mini-em (~1/100 em)
 .El
 .It M
 mini-em (~1/100 em)
 .El


@@ -262,7 +263,6 @@ mini-em (~1/100 em)
 Using anything other than
 .Sq m ,
 .Sq n ,
 Using anything other than
 .Sq m ,
 .Sq n ,

-.Sq u ,

 or
 .Sq v
 is necessarily non-portable across output media.
 or
 .Sq v
 is necessarily non-portable across output media.


@@ -395,46 +395,130 @@ The
 .Xr mandoc 1
 .Nm
 parser recognises the following requests.
 .Xr mandoc 1
 .Nm
 parser recognises the following requests.

-Note that the
-.Nm
-language defines many more requests not implemented in
-.Xr mandoc 1 .
+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.
 .Ss \&ad
 Set line adjustment mode.

-This line-scoped request is intended to have one argument to select
-normal, left, right, or centre adjustment for subsequent text.
-Currently, it is ignored including its arguments,
-and the number of arguments is not checked.
+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 \&am
 Append to a macro definition.
 The syntax of this request is the same as that of
 .Sx \&de .

-It is currently ignored by
-.Xr mandoc 1 ,
-as are its children.
-.Ss \&ami
-Append to a macro definition, specifying the macro name indirectly.
-The syntax of this request is the same as that of
-.Sx \&dei .
-It is currently ignored by
-.Xr mandoc 1 ,
-as are its children.

 .Ss \&am1
 Append to a macro definition, switching roff compatibility mode off
 .Ss \&am1
 Append to a macro definition, switching roff compatibility mode off

-during macro execution.
+during macro execution (groff extension).

 The syntax of this request is the same as that of
 .Sx \&de1 .
 The syntax of this request is the same as that of
 .Sx \&de1 .

-It is currently ignored by
-.Xr mandoc 1 ,
-as are its children.
+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 \&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
 .Ss \&cc

-Changes the control character.
+Change the control character.

 Its syntax is as follows:
 .Bd -literal -offset indent
 .Pf . Cm \&cc Op Ar c
 Its syntax is as follows:
 .Bd -literal -offset indent
 .Pf . Cm \&cc Op Ar c


@@ -447,10 +531,63 @@ is not specified, the control character is reset to
 Trailing characters are ignored.
 .Ss \&ce
 Center some lines.
 Trailing characters are ignored.
 .Ss \&ce
 Center some lines.

-This line-scoped request is intended to take one integer argument,
-specifying how many lines to center.
-Currently, it is ignored including its arguments, and the number
-of arguments is not checked.
+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
 .Ss \&de
 Define a
 .Nm


@@ -528,6 +665,8 @@ produces
 .D1 \efI\e^XtFree\e^\efP.
 .Pp
 in the input stream, and thus in the output: \fI\^XtFree\^\fP.
 .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 blank characters.

 .Pp
 Since macros and user-defined strings share a common string table,
 defining a macro
 .Pp
 Since macros and user-defined strings share a common string table,
 defining a macro


@@ -546,32 +685,66 @@ one explicit newline character.
 In order to prevent endless recursion, both groff and
 .Xr mandoc 1
 limit the stack depth for expanding macros and strings
 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.
-Do not rely on the exact value of this limit.
+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
 .Ss \&dei
 Define a
 .Nm

-macro, specifying the macro name indirectly.
+macro, specifying the macro name indirectly (groff extension).

 The syntax of this request is the same as that of
 .Sx \&de .
 The syntax of this request is the same as that of
 .Sx \&de .

-It is currently ignored by
-.Xr mandoc 1 ,
-as are its children.
-.Ss \&de1
+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
 Define a
 .Nm
 macro that will be executed with
 .Nm

-compatibility mode switched off during macro execution.
-This is a GNU extension not available in traditional
-.Nm
-implementations and not even in older versions of groff.
+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
 Since
 .Xr mandoc 1
 does not implement
 .Nm
 compatibility mode at all, it handles this request as an alias for

-.Sx \&de .
+.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:
 .Ss \&ds
 Define a user-defined string.
 Its syntax is as follows:


@@ -630,6 +803,32 @@ macro when used in a
 .Xr man 7
 document.
 Such abuse is of course strongly discouraged.
 .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
 .Ss \&el
 The
 .Qq else


@@ -644,27 +843,171 @@ then false is assumed.
 The syntax of this request is similar to
 .Sx \&if
 except that the conditional is missing.
 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 \&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 \&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.
 .Ss \&fam
 Change the font family.

-This line-scoped request is intended to have one argument specifying
-the font family to be selected.
-It is a groff extension, and currently, it is ignored including its
-arguments, and the number of arguments is not checked.
+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.
 .Ss \&hw
 Specify hyphenation points in words.

-This line-scoped request is currently ignored.
+Currently ignored.

 .Ss \&hy
 Set automatic hyphenation mode.
 .Ss \&hy
 Set automatic hyphenation mode.

-This line-scoped request is currently ignored.
+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
 .Ss \&ie
 The
 .Qq if


@@ -677,10 +1020,72 @@ Its syntax is equivalent to
 .Sx \&if .
 .Ss \&if
 Begins a conditional.
 .Sx \&if .
 .Ss \&if
 Begins a conditional.

-Right now, the conditional evaluates to true
-if and only if it starts with the letter
-.Sy n ,
-indicating processing in nroff style as opposed to troff style.
+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 evaluates 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.
 If a conditional is false, its children are not processed, but are
 syntactically interpreted to preserve the integrity of the input
 document.


@@ -698,44 +1103,12 @@ 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.
 conditional.
 Sub-conditionals, in this case, obviously inherit the truth value of
 the parent.

-This request has the following syntax:
-.Bd -literal -offset indent
-\&.if COND \e{\e
-BODY...
-\&.\e}
-.Ed
-.Bd -literal -offset indent
-\&.if COND \e{ BODY
-BODY... \e}
-.Ed
-.Bd -literal -offset indent
-\&.if COND \e{ BODY
-BODY...
-\&.\e}
-.Ed
-.Bd -literal -offset indent
-\&.if COND \e
-BODY
-.Ed
-.Pp
-COND is a conditional statement.
-roff allows for complicated conditionals; mandoc is much simpler.
-At this time, mandoc supports only
-.Sq n ,
-evaluating to true;
-and
-.Sq t ,
-.Sq e ,
-and
-.Sq o ,
-evaluating to false.
-All other invocations are read up to the next end of line or space and
-evaluate as false.

 .Pp
 If the BODY section is begun by an escaped brace
 .Sq \e{ ,
 .Pp
 If the BODY section is begun by an escaped brace
 .Sq \e{ ,

-scope continues until a closing-brace escape sequence
-.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
 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


@@ -815,30 +1188,175 @@ Otherwise, it only terminates the
 and arguments following it or the
 .Sq \&..
 request are discarded.
 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.
 .Ss \&ne
 Declare the need for the specified minimum vertical space
 before the next trap or the bottom of the page.

-This line-scoped request is currently ignored.
+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.
 .Ss \&nh
 Turn off automatic hyphenation mode.

-This line-scoped request is currently ignored.
-.Ss \&rm
-Remove a request, macro or string.
-This request is intended to have one argument,
-the name of the request, macro or string to be undefined.
-Currently, it is ignored including its arguments,
-and the number of arguments is not checked.
+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
+Execute 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
 .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 value
+.D1 Pf \. Cm \&nr Ar name Oo +|- Oc Ns Ar expression

 .Pp
 .Pp

-The
-.Ar value
-may, at the moment, only be an integer.
+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
 If it is prefixed by a sign, the register will be
 incremented or decremented instead of assigned to.
 .Pp


@@ -863,16 +1381,142 @@ section with the
 .Cm \&Sh
 macro will reset this register.
 .El
 .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.
 .Ss \&ns
 Turn on no-space mode.

-This line-scoped request is intended to take no arguments.
-Currently, it is ignored including its arguments,
-and the number of arguments is not checked.
+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.
 .Ss \&ps
 Change point size.

-This line-scoped request is intended to take one numerical argument.
-Currently, it is ignored including its arguments,
-and the number of arguments is not checked.
+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:
 .Ss \&so
 Include a source file.
 Its syntax is as follows:


@@ -906,10 +1550,64 @@ is discouraged.
 Use
 .Xr ln 1
 instead.
 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.
 .Ss \&ta
 Set tab stops.

-This line-scoped request can take an arbitrary number of arguments.
-Currently, it is ignored including its arguments.
+Takes an arbitrary number of arguments.
+Currently unsupported.
+.Ss \&tc
+Change tab repetition 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:
 .Ss \&tr
 Output character translation.
 Its syntax is as follows:


@@ -927,20 +1625,163 @@ Replacement (or origin) characters may also be character escapes; thus,
 .Dl tr \e(xx\e(yy
 .Pp
 replaces all invocations of \e(xx with \e(yy.
 .Dl tr \e(xx\e(yy
 .Pp
 replaces all invocations of \e(xx with \e(yy.

-.Ss \&T&
-Re-start a table layout, retaining the options of the prior table
-invocation.
-See
-.Sx \&TS .
-.Ss \&TE
-End a table context.
-See
-.Sx \&TS .
+.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 \&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 specified 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 precedence; 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
 .Sh ESCAPE SEQUENCE REFERENCE
 The
 .Xr mandoc 1


@@ -998,9 +1839,15 @@ For short names, there are variants
 .No \e* Ns Ar c
 and
 .No \e*( Ns Ar cc .
 .No \e* Ns Ar c
 and
 .No \e*( Ns Ar cc .

+.Ss \e,
+Left italic correction (groff extension); ignored by
+.Xr mandoc 1 .

 .Ss \e-
 Special character
 .Dq mathematical minus sign .
 .Ss \e-
 Special character
 .Dq mathematical minus sign .

+.Ss \e/
+Right italic correction (groff extension); ignored by
+.Xr mandoc 1 .

 .Ss \e[ Ns Ar name ]
 .Sx Special Characters
 with names of arbitrary length, see
 .Ss \e[ Ns Ar name ]
 .Sx Special Characters
 with names of arbitrary length, see


@@ -1029,10 +1876,15 @@ Digit width space character.
 Anchor definition; ignored by
 .Xr mandoc 1 .
 .Ss \eB\(aq Ns Ar string Ns \(aq
 Anchor definition; ignored by
 .Xr mandoc 1 .
 .Ss \eB\(aq Ns Ar string Ns \(aq

-Test whether
+Interpolate
+.Sq 1
+if

 .Ar string
 .Ar string

-is a numerical expession; ignored by
-.Xr mandoc 1 .
+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 \eb\(aq Ns Ar string Ns \(aq
 Bracket building function; ignored by
 .Xr mandoc 1 .


@@ -1040,8 +1892,10 @@ Bracket building function; ignored by
 .Sx Special Characters
 with names of arbitrary length.
 .Ss \ec
 .Sx Special Characters
 with names of arbitrary length.
 .Ss \ec

-Interrupt text processing to insert requests or macros; ignored by
-.Xr mandoc 1 .
+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\(aq Ns Ar string Ns \(aq
 Draw graphics function; ignored by
 .Xr mandoc 1 .


@@ -1118,10 +1972,11 @@ For short names, there are variants
 and
 .No \en( Ns Ar cc .
 .Ss \eo\(aq Ns Ar string Ns \(aq
 and
 .No \en( Ns Ar cc .
 .Ss \eo\(aq Ns Ar string Ns \(aq

-Overstrike
-.Ar string ;
-ignored by
-.Xr mandoc 1 .
+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 \eR\(aq Ns Ar name Oo +|- Oc Ns Ar number Ns \(aq
 Set number register; ignored by
 .Xr mandoc 1 .


@@ -1156,9 +2011,13 @@ Vertical motion; ignored by
 .Xr mandoc 1 .
 .Ss \ew\(aq Ns Ar string Ns \(aq
 Interpolate the width of the
 .Xr mandoc 1 .
 .Ss \ew\(aq Ns Ar string Ns \(aq
 Interpolate the width of the

-.Ar string ;
-ignored by
-.Xr mandoc 1 .
+.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
 .Ss \eX\(aq Ns Ar string Ns \(aq
 Output
 .Ar string


@@ -1180,49 +2039,68 @@ Print
 with zero width and height; ignored by
 .Xr mandoc 1 .
 .Ss \ez
 with zero width and height; ignored by
 .Xr mandoc 1 .
 .Ss \ez

-Output the next character without advancing the cursor position;
-approximated in
-.Xr mandoc 1
-by simply skipping the next character.
+Output the next character without advancing the cursor position.

 .Sh COMPATIBILITY
 .Sh COMPATIBILITY

-This section documents compatibility between mandoc and other
+The
+.Xr mandoc 1
+implementation of the

 .Nm
 .Nm

-implementations, at this time limited to GNU troff
-.Pq Qq groff .
-The term
-.Qq historic groff
-refers to groff version 1.15.
+language is intentionally incomplete.
+Unimplemented features include:

 .Pp
 .Bl -dash -compact
 .It
 .Pp
 .Bl -dash -compact
 .It

-In mandoc, the
-.Sx \&EQ ,
-.Sx \&TE ,
-.Sx \&TS ,
-and
-.Sx \&T& ,
-macros are considered regular macros.
-In all other
-.Nm
-implementations, these are special macros that must be specified without
-spacing between the control character (which must be a period) and the
-macro name.
+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
 .It
 The

-.Cm nS
-register is only compatible with OpenBSD's groff-1.15.
+.Sq u
+scaling unit is the default terminal unit.
+In traditional troff systems, this unit changes depending on the
+output media.

 .It
 .It

-Historic groff did not accept white-space before a custom
-.Ar end
-macro for the
-.Sx \&ig
-request.
+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
 .It
 The

-.Sx \&if
-and family would print funny white-spaces with historic groff when
-using the next-line syntax.
+.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
 .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 ,
 .Sh SEE ALSO
 .Xr mandoc 1 ,
 .Xr eqn 7 ,