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version 1.32, 2011/09/02 19:37:35 version 1.56, 2014/08/13 20:34:29
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 .\"     $Id$  .\"     $Id$
 .\"  .\"
 .\" Copyright (c) 2010 Kristaps Dzonsons <kristaps@bsd.lv>  .\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
 .\" Copyright (c) 2010 Ingo Schwarze <schwarze@openbsd.org>  .\" Copyright (c) 2010, 2011, 2013, 2014 Ingo Schwarze <schwarze@openbsd.org>
 .\"  .\"
 .\" Permission to use, copy, modify, and distribute this software for any  .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above  .\" purpose with or without fee is hereby granted, provided that the above
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 The  The
 .Nm roff  .Nm roff
 language is a general purpose text formatting language.  language is a general purpose text formatting language.
 In particular, it serves as the basis for the  Since traditional implementations of the
 .Xr mdoc 7  .Xr mdoc 7
 and  and
 .Xr man 7  .Xr man 7
 manual formatting macro languages.  manual formatting languages are based on it,
 This manual describes the subset of the  many real-world manuals use small numbers of
 .Nm  .Nm
 language accepted by the  requests and escape sequences intermixed with their
   .Xr mdoc 7
   or
   .Xr man 7
   code.
   To properly format such manuals, the
 .Xr mandoc 1  .Xr mandoc 1
 utility.  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  .Pp
 Input lines beginning with the control characters  Input lines beginning with the control character
 .Sq \&.  .Sq \&.
 or  
 .Sq \(aq  
 are parsed for requests and macros.  are parsed for requests and macros.
 These define the document structure, change the processing state  Such lines are called
 and manipulate the formatting.  .Dq request lines
 Some requests and macros also produce formatted output,  or
 while others do not.  .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  .Pp
 All other input lines provide free-form text to be printed;  Lines not beginning with control characters are called
 the formatting of free-form text depends on the respective  .Dq text lines .
 processing context.  They provide free-form text to be printed; the formatting of the text
   depends on the respective processing context.
 .Sh LANGUAGE SYNTAX  .Sh LANGUAGE SYNTAX
 .Nm  .Nm
 documents may contain only graphable 7-bit ASCII characters, the space  documents may contain only graphable 7-bit ASCII characters, the space
 character, and, in certain circumstances, the tab character.  character, and, in certain circumstances, the tab character.
 To produce other characters in the output, use the escape sequences  The backslash character
 documented in the  .Sq \e
   indicates the start of an escape sequence, used for example for
   .Sx Comments ,
   .Sx Special Characters ,
   .Sx Predefined Strings ,
   and
   user-defined strings defined using the
   .Sx ds
   request.
   For a listing of escape sequences, consult the
   .Sx ESCAPE SEQUENCE REFERENCE
   below.
   .Ss Comments
   Text following an escaped double-quote
   .Sq \e\(dq ,
   whether in a request, macro, or text line, is ignored to the end of the line.
   A request line beginning with a control character and comment escape
   .Sq \&.\e\(dq
   is also ignored.
   Furthermore, request lines with only a control character and optional
   trailing whitespace are stripped from input.
   .Pp
   Examples:
   .Bd -literal -offset indent -compact
   \&.\e\(dq This is a comment line.
   \&.\e\(dq The next line is ignored:
   \&.
   \&.Sh EXAMPLES \e\(dq This is a comment, too.
   \&example text \e\(dq And so is this.
   .Ed
   .Ss Special Characters
   Special characters are used to encode special glyphs and are rendered
   differently across output media.
   They may occur in request, macro, and text lines.
   Sequences begin with the escape character
   .Sq \e
   followed by either an open-parenthesis
   .Sq \&(
   for two-character sequences; an open-bracket
   .Sq \&[
   for n-character sequences (terminated at a close-bracket
   .Sq \&] ) ;
   or a single one character sequence.
   .Pp
   Examples:
   .Bl -tag -width Ds -offset indent -compact
   .It Li \e(em
   Two-letter em dash escape.
   .It Li \ee
   One-letter backslash escape.
   .El
   .Pp
   See
 .Xr mandoc_char 7  .Xr mandoc_char 7
 manual.  for a complete list.
   .Ss Text Decoration
   Terms may be text-decorated using the
   .Sq \ef
   escape followed by an indicator: B (bold), I (italic), R (regular), or P
   (revert to previous mode).
   A numerical representation 3, 2, or 1 (bold, italic, and regular,
   respectively) may be used instead.
   The indicator or numerical representative may be preceded by C
   (constant-width), which is ignored.
   .Pp
   The two-character indicator
   .Sq BI
   requests a font that is both bold and italic.
   It may not be portable to old roff implementations.
   .Pp
   Examples:
   .Bl -tag -width Ds -offset indent -compact
   .It Li \efBbold\efR
   Write in \fBbold\fP, then switch to regular font mode.
   .It Li \efIitalic\efP
   Write in \fIitalic\fP, then return to previous font mode.
   .It Li \ef(BIbold italic\efP
   Write in \f(BIbold italic\fP, then return to previous font mode.
   .El
   .Pp
   Text decoration is
   .Em not
   recommended for
   .Xr mdoc 7 ,
   which encourages semantic annotation.
   .Ss Predefined Strings
   Predefined strings, like
   .Sx Special Characters ,
   mark special output glyphs.
   Predefined strings are escaped with the slash-asterisk,
   .Sq \e* :
   single-character
   .Sq \e*X ,
   two-character
   .Sq \e*(XX ,
   and N-character
   .Sq \e*[N] .
   .Pp
   Examples:
   .Bl -tag -width Ds -offset indent -compact
   .It Li \e*(Am
   Two-letter ampersand predefined string.
   .It Li \e*q
   One-letter double-quote predefined string.
   .El
   .Pp
   Predefined strings are not recommended for use,
   as they differ across implementations.
   Those supported by
   .Xr mandoc 1
   are listed in
   .Xr mandoc_char 7 .
   Manuals using these predefined strings are almost certainly not portable.
   .Ss Whitespace
   Whitespace consists of the space character.
   In text lines, whitespace is preserved within a line.
   In request and macro lines, whitespace delimits arguments and is discarded.
   .Pp
   Unescaped trailing spaces are stripped from text line input unless in a
   literal context.
   In general, trailing whitespace on any input line is discouraged for
   reasons of portability.
   In the rare case that a blank character is needed at the end of an
   input line, it may be forced by
   .Sq \e\ \e& .
   .Pp
   Literal space characters can be produced in the output
   using escape sequences.
   In macro lines, they can also be included in arguments using quotation; see
   .Sx MACRO SYNTAX
   for details.
   .Pp
   Blank text lines, which may include whitespace, are only permitted
   within literal contexts.
   If the first character of a text line is a space, that line is printed
   with a leading newline.
   .Ss Scaling Widths
   Many requests and macros support scaled widths for their arguments.
   The syntax for a scaled width is
   .Sq Li [+-]?[0-9]*.[0-9]*[:unit:] ,
   where a decimal must be preceded or followed by at least one digit.
   Negative numbers, while accepted, are truncated to zero.
   .Pp
   The following scaling units are accepted:
   .Pp
   .Bl -tag -width Ds -offset indent -compact
   .It c
   centimetre
   .It i
   inch
   .It P
   pica (~1/6 inch)
   .It p
   point (~1/72 inch)
   .It f
   scale
   .Sq u
   by 65536
   .It v
   default vertical span
   .It m
   width of rendered
   .Sq m
   .Pq em
   character
   .It n
   width of rendered
   .Sq n
   .Pq en
   character
   .It u
   default horizontal span for the terminal
   .It M
   mini-em (~1/100 em)
   .El
   .Pp
   Using anything other than
   .Sq m ,
   .Sq n ,
   or
   .Sq v
   is necessarily non-portable across output media.
   See
   .Sx COMPATIBILITY .
   .Pp
   If a scaling unit is not provided, the numerical value is interpreted
   under the default rules of
   .Sq v
   for vertical spaces and
   .Sq u
   for horizontal ones.
   .Pp
   Examples:
   .Bl -tag -width ".Bl -tag -width 2i" -offset indent -compact
   .It Li \&.Bl -tag -width 2i
   two-inch tagged list indentation in
   .Xr mdoc 7
   .It Li \&.HP 2i
   two-inch tagged list indentation in
   .Xr man 7
   .It Li \&.sp 2v
   two vertical spaces
   .El
   .Ss Sentence Spacing
   Each sentence should terminate at the end of an input line.
   By doing this, a formatter will be able to apply the proper amount of
   spacing after the end of sentence (unescaped) period, exclamation mark,
   or question mark followed by zero or more non-sentence closing
   delimiters
   .Po
   .Sq \&) ,
   .Sq \&] ,
   .Sq \&' ,
   .Sq \&"
   .Pc .
   .Pp
   The proper spacing is also intelligently preserved if a sentence ends at
   the boundary of a macro line.
   .Pp
   Examples:
   .Bd -literal -offset indent -compact
   Do not end sentences mid-line like this.  Instead,
   end a sentence like this.
   A macro would end like this:
   \&.Xr mandoc 1 \&.
   .Ed
 .Sh REQUEST SYNTAX  .Sh REQUEST SYNTAX
 A request or macro line consists of:  A request or macro line consists of:
 .Pp  .Pp
Line 83  Thus, the following request lines are all equivalent:
Line 336  Thus, the following request lines are all equivalent:
 \&.   ig end  \&.   ig end
 .Ed  .Ed
 .Sh MACRO SYNTAX  .Sh MACRO SYNTAX
 Macros can be defined by the  Macros are provided by the
   .Xr mdoc 7
   and
   .Xr man 7
   languages and can be defined by the
 .Sx \&de  .Sx \&de
 request.  request.
 When called, they follow the same syntax as requests, except that  When called, they follow the same syntax as requests, except that
 macro arguments may optionally be quoted by enclosing them  macro arguments may optionally be quoted by enclosing them
 in double quote characters  in double quote characters
 .Pq Sq \(dq .  .Pq Sq \(dq .
 To be recognised as the beginning of a quoted argument, the opening  Quoted text, even if it contains whitespace or would cause
 quote character must be preceded by a space character.  a macro invocation when unquoted, is always considered literal text.
 .Pp  Inside quoted text, pairs of double quote characters
 A quoted argument may contain whitespace, and pairs of double quote  
 characters  
 .Pq Sq Qq  .Pq Sq Qq
 resolve to single double quote characters.  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  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.  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  Leaving out the terminating double quote character at the end of the line
Line 114  In unquoted arguments, space characters can alternativ
Line 372  In unquoted arguments, space characters can alternativ
 by preceding them with a backslash  by preceding them with a backslash
 .Pq Sq \e\~ ,  .Pq Sq \e\~ ,
 but quoting is usually better for clarity.  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  .Sh REQUEST REFERENCE
 The  The
 .Xr mandoc 1  .Xr mandoc 1
Line 133  and the number of arguments is not checked.
Line 409  and the number of arguments is not checked.
 Append to a macro definition.  Append to a macro definition.
 The syntax of this request is the same as that of  The syntax of this request is the same as that of
 .Sx \&de .  .Sx \&de .
 It is currently ignored by  
 .Xr mandoc 1 ,  
 as are its children.  
 .Ss \&ami  .Ss \&ami
 Append to a macro definition, specifying the macro name indirectly.  Append to a macro definition, specifying the macro name indirectly.
 The syntax of this request is the same as that of  The syntax of this request is the same as that of
 .Sx \&dei .  .Sx \&dei .
 It is currently ignored by  
 .Xr mandoc 1 ,  
 as are its children.  
 .Ss \&am1  .Ss \&am1
 Append to a macro definition, switching roff compatibility mode off  Append to a macro definition, switching roff compatibility mode off
 during macro execution.  during macro execution.
 The syntax of this request is the same as that of  The syntax of this request is the same as that of
 .Sx \&de1 .  .Sx \&de1 .
 It is currently ignored by  Since
 .Xr mandoc 1 ,  .Xr mandoc 1
 as are its children.  does not implement
   .Nm
   compatibility mode at all, it handles this request as an alias for
   .Sx \&am .
   .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 \&cc
   Changes the control character.
   Its syntax is as follows:
   .Bd -literal -offset indent
   .Pf . Cm \&cc Op Ar c
   .Ed
   .Pp
   If
   .Ar c
   is not specified, the control character is reset to
   .Sq \&. .
   Trailing characters are ignored.
   .Ss \&ce
   Center some lines.
   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.
 .Ss \&de  .Ss \&de
 Define a  Define a
 .Nm  .Nm
Line 254  Define a
Line 551  Define a
 macro, specifying the macro name indirectly.  macro, specifying the macro name indirectly.
 The syntax of this request is the same as that of  The syntax of this request is the same as that of
 .Sx \&de .  .Sx \&de .
 It is currently ignored by  The request
 .Xr mandoc 1 ,  .Pp
 as are its children.  .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 \&de1  .Ss \&de1
 Define a  Define a
 .Nm  .Nm
Line 353  Begin an equation block.
Line 654  Begin an equation block.
 See  See
 .Xr eqn 7  .Xr eqn 7
 for a description of the equation language.  for a description of the equation language.
   .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.
   .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 \&hw
   Specify hyphenation points in words.
   This line-scoped request is currently ignored.
 .Ss \&hy  .Ss \&hy
 Set automatic hyphenation mode.  Set automatic hyphenation mode.
 This line-scoped request is currently ignored.  This line-scoped request is currently ignored.
Line 368  Its syntax is equivalent to
Line 706  Its syntax is equivalent to
 .Sx \&if .  .Sx \&if .
 .Ss \&if  .Ss \&if
 Begins a conditional.  Begins a conditional.
 Right now, the conditional evaluates to true  This request has the following syntax:
 if and only if it starts with the letter  .Bd -literal -offset indent
 .Sy n ,  \&.if COND BODY
 indicating processing in nroff style as opposed to troff style.  .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 r
   .Pq register accessed ,
   or
   .Sq t
   .Pq troff mode ,
   COND 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 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  If a conditional is false, its children are not processed, but are
 syntactically interpreted to preserve the integrity of the input  syntactically interpreted to preserve the integrity of the input
 document.  document.
Line 389  will continue to syntactically interpret to the block 
Line 784  will continue to syntactically interpret to the block 
 conditional.  conditional.
 Sub-conditionals, in this case, obviously inherit the truth value of  Sub-conditionals, in this case, obviously inherit the truth value of
 the parent.  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  .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  If the BODY section is begun by an escaped brace
 .Sq \e{ ,  .Sq \e{ ,
 scope continues until a closing-brace escape sequence  scope continues until the end of the input line containing the
 .Sq \.\e} .  matching closing-brace escape sequence
   .Sq \e} .
 If the BODY is not enclosed in braces, scope continues until  If the BODY is not enclosed in braces, scope continues until
 the end of the line.  the end of the line.
 If the COND is followed by a BODY on the same line, whether after a  If the COND is followed by a BODY on the same line, whether after a
Line 506  Otherwise, it only terminates the
Line 869  Otherwise, it only terminates the
 and arguments following it or the  and arguments following it or the
 .Sq \&..  .Sq \&..
 request are discarded.  request are discarded.
   .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 \&ne  .Ss \&ne
 Declare the need for the specified minimum vertical space  Declare the need for the specified minimum vertical space
 before the next trap or the bottom of the page.  before the next trap or the bottom of the page.
Line 513  This line-scoped request is currently ignored.
Line 893  This line-scoped request is currently ignored.
 .Ss \&nh  .Ss \&nh
 Turn off automatic hyphenation mode.  Turn off automatic hyphenation mode.
 This line-scoped request is currently ignored.  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.  
 .Ss \&nr  .Ss \&nr
 Define a register.  Define or change a register.
 A register is an arbitrary string value that defines some sort of state,  A register is an arbitrary string value that defines some sort of state,
 which influences parsing and/or formatting.  which influences parsing and/or formatting.
 Its syntax is as follows:  Its syntax is as follows:
 .Pp  .Pp
 .D1 Pf \. Cm \&nr Ar name Ar value  .D1 Pf \. Cm \&nr Ar name Oo +|- Oc Ns Ar expression
 .Pp  .Pp
 The  For the syntax of
 .Ar value  .Ar expression ,
 may, at the moment, only be an integer.  see
 So far, only the following register  .Sx Numerical expressions
   below.
   If it is prefixed by a sign, the register will be
   incremented or decremented instead of assigned to.
   .Pp
   The following register
 .Ar name  .Ar name
 is recognised:  is handled specially:
 .Bl -tag -width Ds  .Bl -tag -width Ds
 .It Cm nS  .It Cm nS
 If set to a positive integer value, certain  If set to a positive integer value, certain
Line 561  Change point size.
Line 940  Change point size.
 This line-scoped request is intended to take one numerical argument.  This line-scoped request is intended to take one numerical argument.
 Currently, it is ignored including its arguments,  Currently, it is ignored including its arguments,
 and the number of arguments is not checked.  and the number of arguments is not checked.
   .Ss \&rm
   Remove a request, macro or string.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Cm \&rm Ar name
   .Ss \&rr
   Remove a register.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Cm \&rr Ar name
 .Ss \&so  .Ss \&so
 Include a source file.  Include a source file.
 Its syntax is as follows:  Its syntax is as follows:
Line 578  only accepts relative paths not containing the strings
Line 967  only accepts relative paths not containing the strings
 .Qq ../  .Qq ../
 and  and
 .Qq /.. .  .Qq /.. .
   .Pp
   This request requires
   .Xr man 1
   to change to the right directory before calling
   .Xr mandoc 1 ,
   per convention to the root of the manual tree.
   Typical usage looks like:
   .Pp
   .Dl \&.so man3/Xcursor.3
   .Pp
   As the whole concept is rather fragile, the use of
   .Sx \&so
   is discouraged.
   Use
   .Xr ln 1
   instead.
 .Ss \&ta  .Ss \&ta
 Set tab stops.  Set tab stops.
 This line-scoped request can take an arbitrary number of arguments.  This line-scoped request can take an arbitrary number of arguments.
Line 613  Begin a table, which formats input in aligned rows and
Line 1018  Begin a table, which formats input in aligned rows and
 See  See
 .Xr tbl 7  .Xr tbl 7
 for a description of the tbl language.  for a description of the tbl language.
   .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 - .
   .Pp
   The following binary operators are implemented.
   Unless otherwise stated, they behave as in the C language:
   .Pp
   .Bl -tag -width 2n -compact
   .It Ic +
   addition
   .It Ic -
   subtraction
   .It Ic *
   multiplication
   .It Ic /
   division
   .It Ic %
   remainder of division
   .It Ic <
   less than
   .It Ic >
   greater than
   .It Ic ==
   equal to
   .It Ic =
   equal to, same effect as
   .Ic ==
   (this differs from C)
   .It Ic <=
   less than or equal to
   .It Ic >=
   greater than or equal to
   .It Ic <>
   not equal to (corresponds to C
   .Ic != ;
   this one is of limited portability, it is supported by Heirloom roff,
   but not by groff)
   .It Ic &
   logical and (corresponds to C
   .Ic && )
   .It Ic \&:
   logical or (corresponds to C
   .Ic \&|| )
   .It Ic <?
   minimum (not available in C)
   .It Ic >?
   maximum (not available in C)
   .El
   .Pp
   There is no concept of precendence; evaluation proceeds from left to right,
   except when subexpressions are enclosed in parantheses.
   Inside parentheses, whitespace is ignored.
   .Sh ESCAPE SEQUENCE REFERENCE
   The
   .Xr mandoc 1
   .Nm
   parser recognises the following escape sequences.
   Note that the
   .Nm
   language defines more escape sequences not implemented in
   .Xr mandoc 1 .
   In
   .Xr mdoc 7
   and
   .Xr man 7
   documents, using escape sequences is discouraged except for those
   described in the
   .Sx LANGUAGE SYNTAX
   section above.
   .Pp
   A backslash followed by any character not listed here
   simply prints that character itself.
   .Ss \e<newline>
   A backslash at the end of an input line can be used to continue the
   logical input line on the next physical input line, joining the text
   on both lines together as if it were on a single input line.
   .Ss \e<space>
   The escape sequence backslash-space
   .Pq Sq \e\ \&
   is an unpaddable space-sized non-breaking space character; see
   .Sx Whitespace .
   .Ss \e\(dq
   The rest of the input line is treated as
   .Sx Comments .
   .Ss \e%
   Hyphenation allowed at this point of the word; ignored by
   .Xr mandoc 1 .
   .Ss \e&
   Non-printing zero-width character; see
   .Sx Whitespace .
   .Ss \e\(aq
   Acute accent special character; use
   .Sq \e(aa
   instead.
   .Ss \e( Ns Ar cc
   .Sx Special Characters
   with two-letter names, see
   .Xr mandoc_char 7 .
   .Ss \e*[ Ns Ar name ]
   Interpolate the string with the
   .Ar name ;
   see
   .Sx Predefined Strings
   and
   .Sx ds .
   For short names, there are variants
   .No \e* Ns Ar c
   and
   .No \e*( Ns Ar cc .
   .Ss \e-
   Special character
   .Dq mathematical minus sign .
   .Ss \e[ Ns Ar name ]
   .Sx Special Characters
   with names of arbitrary length, see
   .Xr mandoc_char 7 .
   .Ss \e^
   One-twelfth em half-narrow space character, effectively zero-width in
   .Xr mandoc 1 .
   .Ss \e`
   Grave accent special character; use
   .Sq \e(ga
   instead.
   .Ss \e{
   Begin conditional input; see
   .Sx if .
   .Ss \e\(ba
   One-sixth em narrow space character, effectively zero-width in
   .Xr mandoc 1 .
   .Ss \e}
   End conditional input; see
   .Sx if .
   .Ss \e~
   Paddable non-breaking space character.
   .Ss \e0
   Digit width space character.
   .Ss \eA\(aq Ns Ar string Ns \(aq
   Anchor definition; ignored by
   .Xr mandoc 1 .
   .Ss \eB\(aq Ns Ar string Ns \(aq
   Interpolate
   .Sq 1
   if
   .Ar string
   conforms to the syntax of
   .Sx Numerical expressions
   explained above and
   .Sq 0
   otherwise.
   .Ss \eb\(aq Ns Ar string Ns \(aq
   Bracket building function; ignored by
   .Xr mandoc 1 .
   .Ss \eC\(aq Ns Ar name Ns \(aq
   .Sx Special Characters
   with names of arbitrary length.
   .Ss \ec
   Interrupt text processing to insert requests or macros; ignored by
   .Xr mandoc 1 .
   .Ss \eD\(aq Ns Ar string Ns \(aq
   Draw graphics function; ignored by
   .Xr mandoc 1 .
   .Ss \ed
   Move down by half a line; ignored by
   .Xr mandoc 1 .
   .Ss \ee
   Backslash special character.
   .Ss \eF[ Ns Ar name ]
   Switch font family (groff extension); ignored by
   .Xr mandoc 1 .
   For short names, there are variants
   .No \eF Ns Ar c
   and
   .No \eF( Ns Ar cc .
   .Ss \ef[ Ns Ar name ]
   Switch to the font
   .Ar name ,
   see
   .Sx Text Decoration .
   For short names, there are variants
   .No \ef Ns Ar c
   and
   .No \ef( Ns Ar cc .
   .Ss \eg[ Ns Ar name ]
   Interpolate the format of a number register; ignored by
   .Xr mandoc 1 .
   For short names, there are variants
   .No \eg Ns Ar c
   and
   .No \eg( Ns Ar cc .
   .Ss \eH\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
   Set the height of the current font; ignored by
   .Xr mandoc 1 .
   .Ss \eh\(aq Ns Ar number Ns \(aq
   Horizontal motion; ignored by
   .Xr mandoc 1 .
   .Ss \ek[ Ns Ar name ]
   Mark horizontal input place in register; ignored by
   .Xr mandoc 1 .
   For short names, there are variants
   .No \ek Ns Ar c
   and
   .No \ek( Ns Ar cc .
   .Ss \eL\(aq Ns Ar number Ns Oo Ar c Oc Ns \(aq
   Vertical line drawing function; ignored by
   .Xr mandoc 1 .
   .Ss \el\(aq Ns Ar number Ns Oo Ar c Oc Ns \(aq
   Horizontal line drawing function; ignored by
   .Xr mandoc 1 .
   .Ss \eM[ Ns Ar name ]
   Set fill (background) color (groff extension); ignored by
   .Xr mandoc 1 .
   For short names, there are variants
   .No \eM Ns Ar c
   and
   .No \eM( Ns Ar cc .
   .Ss \em[ Ns Ar name ]
   Set glyph drawing color (groff extension); ignored by
   .Xr mandoc 1 .
   For short names, there are variants
   .No \em Ns Ar c
   and
   .No \em( Ns Ar cc .
   .Ss \eN\(aq Ns Ar number Ns \(aq
   Character
   .Ar number
   on the current font.
   .Ss \en[ Ns Ar name ]
   Interpolate the number register
   .Ar name .
   For short names, there are variants
   .No \en Ns Ar c
   and
   .No \en( Ns Ar cc .
   .Ss \eo\(aq Ns Ar string Ns \(aq
   Overstrike
   .Ar string ;
   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 .
   .Ss \eS\(aq Ns Ar number Ns \(aq
   Slant output; ignored by
   .Xr mandoc 1 .
   .Ss \es\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
   Change point size; ignored by
   .Xr mandoc 1 .
   Alternative forms
   .No \es Ns Oo +|- Oc Ns Ar n ,
   .No \es Ns Oo +|- Oc Ns \(aq Ns Ar number Ns \(aq ,
   .No \es Ns [ Oo +|- Oc Ns Ar number ] ,
   and
   .No \es Ns Oo +|- Oc Ns [ Ar number Ns ]
   are also parsed and ignored.
   .Ss \et
   Horizontal tab; ignored by
   .Xr mandoc 1 .
   .Ss \eu
   Move up by half a line; ignored by
   .Xr mandoc 1 .
   .Ss \eV[ Ns Ar name ]
   Interpolate an environment variable; ignored by
   .Xr mandoc 1 .
   For short names, there are variants
   .No \eV Ns Ar c
   and
   .No \eV( Ns Ar cc .
   .Ss \ev\(aq Ns Ar number Ns \(aq
   Vertical motion; ignored by
   .Xr mandoc 1 .
   .Ss \ew\(aq Ns Ar string Ns \(aq
   Interpolate the width of the
   .Ar string .
   The
   .Xr mandoc 1
   implementation assumes that after expansion of user-defined strings, the
   .Ar string
   only contains normal characters, no escape sequences, and that each
   character has a width of 24 basic units.
   .Ss \eX\(aq Ns Ar string Ns \(aq
   Output
   .Ar string
   as device control function; ignored in nroff mode and by
   .Xr mandoc 1 .
   .Ss \ex\(aq Ns Ar number Ns \(aq
   Extra line space function; ignored by
   .Xr mandoc 1 .
   .Ss \eY[ Ns Ar name ]
   Output a string as a device control function; ignored in nroff mode and by
   .Xr mandoc 1 .
   For short names, there are variants
   .No \eY Ns Ar c
   and
   .No \eY( Ns Ar cc .
   .Ss \eZ\(aq Ns Ar string Ns \(aq
   Print
   .Ar string
   with zero width and height; ignored by
   .Xr mandoc 1 .
   .Ss \ez
   Output the next character without advancing the cursor position;
   approximated in
   .Xr mandoc 1
   by simply skipping the next character.
 .Sh COMPATIBILITY  .Sh COMPATIBILITY
 This section documents compatibility between mandoc and other other  This section documents compatibility between mandoc and other
 .Nm  .Nm
 implementations, at this time limited to GNU troff  implementations, at this time limited to GNU troff
 .Pq Qq groff .  .Pq Qq groff .
Line 624  refers to groff version 1.15.
Line 1348  refers to groff version 1.15.
 .Pp  .Pp
 .Bl -dash -compact  .Bl -dash -compact
 .It  .It
   The
   .Sq u
   scaling unit is the default terminal unit.
   In traditional troff systems, this unit would change depending on the
   output media.
   .It
 In mandoc, the  In mandoc, the
 .Sx \&EQ ,  .Sx \&EQ ,
 .Sx \&TE ,  .Sx \&TE ,
Line 679  using the next-line syntax.
Line 1409  using the next-line syntax.
 .%U http://heirloom.sourceforge.net/doctools/troff.pdf  .%U http://heirloom.sourceforge.net/doctools/troff.pdf
 .Re  .Re
 .Sh HISTORY  .Sh HISTORY
 The RUNOFF typesetting system was written in PL/1 for the CTSS  The RUNOFF typesetting system, whose input forms the basis for
 operating system by Jerome ("Jerry") E. Saltzer in 1961.  
 It was first used as the main documentation tool by Multics since 1963.  
 Robert ("Bob") H. Morris ported it to the GE-635 and called it  
 .Nm ,  .Nm ,
 Doug McIlroy rewrote it in BCPL in 1969,  was written in MAD and FAP for the CTSS operating system by Jerome E.
 Joseph F. Ossanna rewrote it in PDP-11 assembly in 1973,  Saltzer in 1964.
 and Brian W. Kernighan rewrote it in C in 1975.  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  .Sh AUTHORS
 .An -nosplit  .An -nosplit
 This  This
 .Nm  .Nm
 reference was written by  reference was written by
 .An Kristaps Dzonsons ,  .An Kristaps Dzonsons Aq Mt kristaps@bsd.lv
 .Mt kristaps@bsd.lv ;  
 and  and
 .An Ingo Schwarze ,  .An Ingo Schwarze Aq Mt schwarze@openbsd.org .
 .Mt schwarze@openbsd.org .  
Legend:
Removed from v.1.32  
changed lines
  Added in v.1.56
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