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version 1.23, 2009/06/10 20:18:43 version 1.140, 2010/07/19 21:59:48
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 .\"     $Id$  .\"     $Id$
 .\"  .\"
 .\" Copyright (c) 2009 Kristaps Dzonsons <kristaps@kth.se>  .\" Copyright (c) 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
   .\" Copyright (c) 2010 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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 .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN  .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.  .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"  .\"
 .Dd $Mdocdate$  .Dd $Mdocdate$
 .Dt MDOC 7  .Dt MDOC 7
 .Os  .Os
 .\" SECTION  
 .Sh NAME  .Sh NAME
 .Nm mdoc  .Nm mdoc
 .Nd mdoc language reference  .Nd mdoc language reference
 .\" SECTION  
 .Sh DESCRIPTION  .Sh DESCRIPTION
 The  The
 .Nm mdoc  .Nm mdoc
 language is used to format  language is used to format
 .Bx  .Bx
 .Ux  .Ux
 manuals.  In this reference document, we describe the syntax, ontology  manuals.
 and structure of the  In this reference document, we describe its syntax, structure, and
 .Nm  usage.
 language.  Our reference implementation is mandoc; the
 .\" PARAGRAPH  .Sx COMPATIBILITY
   section describes compatibility with other troff \-mdoc implementations.
 .Pp  .Pp
 An  An
 .Nm  .Nm
 document follows simple rules:  lines beginning with the control  document follows simple rules: lines beginning with the control
 character  character
 .Sq \.  .Sq \.
 are parsed for macros.  Other lines are interpreted within the scope of  are parsed for macros.
   Other lines are interpreted within the scope of
 prior macros:  prior macros:
 .Bd -literal -offset XXX  .Bd -literal -offset indent
 \&.Sh Macro lines change control state.  \&.Sh Macro lines change control state.
 Other lines are interpreted within the current state.  Other lines are interpreted within the current state.
 .Ed  .Ed
 .\" SECTION  .Sh LANGUAGE SYNTAX
 .Sh INPUT ENCODING  
 .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  character, and, in certain circumstances, the tab character.
 .Sq \  ,  
 and, in certain circumstances, the tab character  
 .Sq \et .  
 All manuals must have  All manuals must have
 .Sq \en  .Ux
 line termination.  line terminators.
 .Pp  .Ss Comments
 The only time a blank line is acceptable is within  Text following a
 the context of  .Sq \e\*q ,
 .Sq \&.Bd \-literal  whether in a macro or free-form text line, is ignored to the end of
 or  line.
 .Sq \&.Bd \-unfilled .  A macro line with only a control character and comment escape,
 .Pp  .Sq \&.\e\*q ,
 Tab characters  is also ignored.
 .Pq \et  Macro lines with only a control character and optionally whitespace are
 are only acceptable when delimiting  stripped from input.
 .Sq \&.Bl \-column  
 and in  
 .Sq \&.Bd \-literal  
 or  
 .Sq \&.Bd \-unfilled  
 contexts.  
 .\" SUB-SECTION  
 .Ss Reserved Characters  .Ss Reserved Characters
 Within a macro line, the following characters are reserved:  Within a macro line, the following characters are reserved:
 .Bl -tag -width 12n -offset XXXX -compact  .Pp
   .Bl -tag -width Ds -offset indent -compact
 .It \&.  .It \&.
 .Pq period  .Pq period
 .It \&,  .It \&,
Line 95  Within a macro line, the following characters are rese
Line 86  Within a macro line, the following characters are rese
 .It \&?  .It \&?
 .Pq question  .Pq question
 .It \&!  .It \&!
 .Pq exclamation  .Pq exclamation
   .It \&|
   .Pq vertical bar
 .El  .El
 .\" PARAGRAPH  
 .Pp  .Pp
 Use of reserved characters is described in  Use of reserved characters is described in
 .Sx Closure .  .Sx MACRO SYNTAX .
 For general non-reserved use, characters must either be escaped with a  For general use in macro lines, these characters must either be escaped
 non-breaking space  with a non-breaking space
 .Pq Sq \e&  .Pq Sq \e&
 or, if applicable, an appropriate escape-sequence used.  or, if applicable, an appropriate escape sequence used.
 .\" SUB-SECTION  
 .Ss Special Characters  .Ss Special Characters
 Special character sequences begin with the escape character  Special characters may occur in both macro and free-form lines.
   Sequences begin with the escape character
 .Sq \e  .Sq \e
 followed by either an open-parenthesis  followed by either an open-parenthesis
 .Sq \&(  .Sq \&(
 for two-character sequences; an open-bracket  for two-character sequences; an open-bracket
 .Sq \&[  .Sq \&[
 for n-character sequences (terminated at a close-bracket  for n-character sequences (terminated at a close-bracket
 .Sq \&] ) ;  .Sq \&] ) ;
 or a single one-character sequence.  or a single one-character sequence.
   See
   .Xr mandoc_char 7
   for a complete list.
   Examples include
   .Sq \e(em
   .Pq em-dash
   and
   .Sq \ee
   .Pq back-slash .
   .Ss Text Decoration
   Terms may be text-decorated using the
   .Sq \ef
   escape followed by an indicator: B (bold), I, (italic), R (Roman), or P
   (revert to previous mode):
 .Pp  .Pp
 Characters may alternatively be escaped by a slash-asterisk,  .D1 \efBbold\efR \efIitalic\efP
 .Sq \e* ,  
 with the same combinations as described above.  This form is deprecated.  
 .\" SECTION  
 .Sh STRUCTURE  
 Macros are classified in an ontology described by their scope rules.  
 Some macros are allowed to deviate from their classifications to  
 preserve backward-compatibility with old macro combinations still found  
 in the manual corpus.  These are specifically noted on a per-macro  
 basis.  
 .\" SUB-SECTION  
 .Ss Scope  
 .Bl -inset  
 .\" LIST-ITEM  
 .It Em Block  
 macros enclose other block macros, in-line macros or text, and  
 may span multiple lines.  
 .Bl -inset -offset XXXX  
 .\" LIST-ITEM  
 .It Em Full-block  
 macros always span multiple lines.  They consist of zero or  
 more  
 .Qq heads ,  
 subsequent macros or text on the same line following invocation; an  
 optional  
 .Qq body ,  
 which spans subsequent lines of text or macros; and an optional  
 .Qq tail ,  
 macros or text on the same line following closure.  
 .\" LIST-ITEM  
 .It Em Partial-block  
 macros may span multiple lines.  They consists of a optional  
 .Qq head ,  
 text immediately following invocation; always a  
 .Qq body ,  
 text or macros following the head on the same and subsequent lines; and  
 optionally a  
 .Qq tail ,  
 text immediately following closure.  
 .\" LIST-ITEM  
 .It Em In-line  
 macros may only enclose text and span at most a single line.  
 .El  
 .El  
 .\" SUB-SECTION  
 .Ss Closure  
 Closure of a macro's scope depends first on its classification, then  
 on whether it's parsable.  In this table,  
 .Sq BFE  
 refers to block full-explicit and so on.  
 .\" PARAGRAPH  
 .Pp  .Pp
 .Bl -tag -width 12n -offset XXXX -compact  A numerical representation 3, 2, or 1 (bold, italic, and Roman,
 .It BPE , BFE  respectively) may be used instead.
 corresponding explicit closure macro  A text decoration is valid within
 .It BFI  the current font scope only: if a macro opens a font scope alongside
 end-of-file or a corresponding implicit closure macro  its own scope, such as
 .It BPI  .Sx \&Bf
 end-of-line (body may be closed by >0 space-separated  .Cm \&Sy ,
 .Sx Reserved Characters ,  in-scope invocations of
 although block scope will still be open)  .Sq \ef
 .It INL  are only valid within the font scope of the macro.
 end-of-line  If
 .El  .Sq \ef
 .\" PARAGRAPH  is specified outside of any font scope, such as in unenclosed, free-form
   text, it will affect the remainder of the document.
 .Pp  .Pp
 If a macro (block or in-line) is parsable, it may also be closed out by  Note this form is
 one of the following scenarios (unless specifically noted otherwise):  .Em not
 .\" PARAGRAPH  recommended for
   .Nm ,
   which encourages semantic annotation.
   .Ss Predefined Strings
   Historically,
   .Xr groff 1
   also defined a set of package-specific
   .Dq predefined strings ,
   which, like
   .Sx Special Characters ,
   mark special output characters and strings by way of input codes.
   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] .
   See
   .Xr mandoc_char 7
   for a complete list.
   Examples include
   .Sq \e*(Am
   .Pq ampersand
   and
   .Sq \e*(Ba
   .Pq vertical bar .
   .Ss Whitespace
   Whitespace consists of the space character.
   In free-form lines, whitespace is preserved within a line; un-escaped
   trailing spaces are stripped from input (unless in a literal context).
   Blank free-form lines, which may include whitespace, are only permitted
   within literal contexts.
 .Pp  .Pp
 .Bl -dash -offset XXXX -compact  In macro lines, whitespace delimits arguments and is discarded.
 .It  If arguments are quoted, whitespace within the quotes is retained.
 a sequence of >0 space-separated  .Ss Quotation
 .Sx Reserved Characters ,  Macro arguments may be quoted with a double-quote to group
 .It  space-delimited terms or to retain blocks of whitespace.
 another macro,  A quoted argument begins with a double-quote preceded by whitespace.
 .It  The next double-quote not pair-wise adjacent to another double-quote
 end-of-line, or  terminates the literal, regardless of surrounding whitespace.
 .It  .Pp
 completion of a set number of arguments.  This produces tokens
   .Sq a" ,
   .Sq b c ,
   .Sq de ,
   and
   .Sq fg" .
   Note that any quoted term, be it argument or macro, is indiscriminately
   considered literal text.
   Thus, the following produces
   .Sq \&Em a :
   .Bd -literal -offset indent
   \&.Em "Em a"
   .Ed
   .Pp
   In free-form mode, quotes are regarded as opaque text.
   .Ss Dates
   There are several macros in
   .Nm
   that require a date argument.
   The canonical form for dates is the American format:
   .Pp
   .D1 Cm Month Day , Year
   .Pp
   The
   .Cm Day
   value is an optionally zero-padded numeral.
   The
   .Cm Month
   value is the full month name.
   The
   .Cm Year
   value is the full four-digit year.
   .Pp
   Reduced form dates are broken-down canonical form dates:
   .Pp
   .D1 Cm Month , Year
   .D1 Cm Year
   .Pp
   Some examples of valid dates follow:
   .Pp
   .D1 "May, 2009" Pq reduced form
   .D1 "2009" Pq reduced form
   .D1 "May 20, 2009" Pq canonical form
   .Ss Scaling Widths
   Many macros support scaled widths for their arguments, such as
   stipulating a two-inch list indentation with the following:
   .Bd -literal -offset indent
   \&.Bl -tag -width 2i
   .Ed
   .Pp
   The syntax for scaled widths is
   .Sq Li [+-]?[0-9]*.[0-9]*[:unit:] ,
   where a decimal must be preceded or proceeded by at least one digit.
   Negative numbers, while accepted, are truncated to zero.
   The following scaling units are accepted:
   .Pp
   .Bl -tag -width Ds -offset indent -compact
   .It c
   centimetre
   .It i
   inch
   .It P
   pica (~1/6 inch)
   .It p
   point (~1/72 inch)
   .It f
   synonym for
   .Sq u
   .It v
   default vertical span
   .It m
   width of rendered
   .Sq m
   .Pq em
   character
   .It n
   width of rendered
   .Sq n
   .Pq en
   character
   .It u
   default horizontal span
   .It M
   mini-em (~1/100 em)
 .El  .El
 .\" PARAGRAPH  
 .Pp  .Pp
 If >0 space-separated  Using anything other than
 .Sx Reserved Characters  .Sq m ,
 are followed by non-reserved characters, the behaviour differs per  .Sq n ,
 macro.  In general, scope of the macro is closed and re-opened:  .Sq u ,
 subsequent tokens are interpreted as if the scope had just been opened.  or
 In other circumstances, scope is simply closed out.  .Sq v
 .\" SECTION  is necessarily non-portable across output media.
 .Sh SYNTAX  See
 Macros are two or three characters in length.  The syntax of macro  .Sx COMPATIBILITY .
 invocation depends on its classification.  .Ss Sentence Spacing
 .Qq \-arg  When composing a manual, make sure that your sentences end at the end of
 refers to the macro arguments (which may contain zero or more values).  a line.
 In these illustrations,  By doing so, front-ends will be able to apply the proper amount of
 .Sq \&.Yo  spacing after the end of sentence (unescaped) period, exclamation mark,
 opens the scope of a macro, and if specified,  or question mark followed by zero or more non-sentence closing
 .Sq \&.Yc  delimiters (
 closes it out (closure may be implicit at end-of-line or end-of-file).  .Ns Sq \&) ,
 .\" PARAGRAPH  .Sq \&] ,
   .Sq \&' ,
   .Sq \&" ) .
 .Pp  .Pp
 Block full-explicit (may contain head, body, tail).  The proper spacing is also intelligently preserved if a sentence ends at
 .Bd -literal -offset XXXX  the boundary of a macro line, e.g.,
 \&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBhead...\(rB  .Pp
 \(lBbody...\(rB  .D1 \&Xr mandoc 1 \.
 \&.Yc \(lBtail...\(rB  .D1 \&Fl T \&Ns \&Cm ascii \.
   .Sh MANUAL STRUCTURE
   A well-formed
   .Nm
   document consists of a document prologue followed by one or more
   sections.
   .Pp
   The prologue, which consists of (in order) the
   .Sx \&Dd ,
   .Sx \&Dt ,
   and
   .Sx \&Os
   macros, is required for every document.
   .Pp
   The first section (sections are denoted by
   .Sx \&Sh )
   must be the NAME section, consisting of at least one
   .Sx \&Nm
   followed by
   .Sx \&Nd .
   .Pp
   Following that, convention dictates specifying at least the
   .Em SYNOPSIS
   and
   .Em DESCRIPTION
   sections, although this varies between manual sections.
   .Pp
   The following is a well-formed skeleton
   .Nm
   file:
   .Bd -literal -offset indent
   \&.Dd $\&Mdocdate$
   \&.Dt mdoc 7
   \&.Os
   \&.Sh NAME
   \&.Nm foo
   \&.Nd a description goes here
   \&.\e\*q The next is for sections 2, 3, & 9 only.
   \&.\e\*q .Sh LIBRARY
   \&.Sh SYNOPSIS
   \&.Nm foo
   \&.Op Fl options
   \&.Ar
   \&.Sh DESCRIPTION
   The
   \&.Nm
   utility processes files ...
   \&.\e\*q .Sh IMPLEMENTATION NOTES
   \&.\e\*q The next is for sections 2, 3, & 9 only.
   \&.\e\*q .Sh RETURN VALUES
   \&.\e\*q The next is for sections 1, 6, 7, & 8 only.
   \&.\e\*q .Sh ENVIRONMENT
   \&.\e\*q .Sh FILES
   \&.\e\*q The next is for sections 1 & 8 only.
   \&.\e\*q .Sh EXIT STATUS
   \&.\e\*q .Sh EXAMPLES
   \&.\e\*q The next is for sections 1, 4, 6, 7, & 8 only.
   \&.\e\*q .Sh DIAGNOSTICS
   \&.\e\*q The next is for sections 2, 3, & 9 only.
   \&.\e\*q .Sh ERRORS
   \&.\e\*q .Sh SEE ALSO
   \&.\e\*q .Xr foobar 1
   \&.\e\*q .Sh STANDARDS
   \&.\e\*q .Sh HISTORY
   \&.\e\*q .Sh AUTHORS
   \&.\e\*q .Sh CAVEATS
   \&.\e\*q .Sh BUGS
   \&.\e\*q .Sh SECURITY CONSIDERATIONS
 .Ed  .Ed
 .\" PARAGRAPH  
 .Pp  .Pp
 Block full-implicit (may contain zero or more heads, body, no tail).  The sections in a
 .Bd -literal -offset XXXX  .Nm
 \&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBhead... \(lBTa head...\(rB\(rB  document are conventionally ordered as they appear above.
 \(lBbody...\(rB  Sections should be composed as follows:
 \&.Yc  .Bl -ohang -offset Ds
   .It Em NAME
   The name(s) and a short description of the documented material.
   The syntax for this as follows:
   .Bd -literal -offset indent
   \&.Nm name0
   \&.Nm name1
   \&.Nm name2
   \&.Nd a short description
 .Ed  .Ed
 .\" PARAGRAPH  
 .Pp  .Pp
 Block partial-explicit (may contain head, multi-line body, tail).  The
 .Bd -literal -offset XXXX  .Sx \&Nm
 \&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBhead...\(rB  macro(s) must precede the
 \(lBbody...\(rB  .Sx \&Nd
 \&.Yc \(lBtail...\(rB  macro.
   .Pp
 \&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBhead...\(rB \  See
 \(lBbody...\(rB \&Yc \(lBtail...\(rB  .Sx \&Nm
   and
   .Sx \&Nd .
   .It Em LIBRARY
   The name of the library containing the documented material, which is
   assumed to be a function in a section 2, 3, or 9 manual.
   The syntax for this is as follows:
   .Bd -literal -offset indent
   \&.Lb libarm
 .Ed  .Ed
 .\" PARAGRAPH  
 .Pp  .Pp
 Block partial-implicit (no head, body, no tail).  Note that the body  See
 section may be followed by zero or more  .Sx \&Lb .
 .Sx Reserved Words .  .It Em SYNOPSIS
 These are in the block scope, but not in the body scope.  Documents the utility invocation syntax, function call syntax, or device
 .Bd -literal -offset XXXX  configuration.
 \&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBbody...\(rB \(lBreserved...\(rB  .Pp
   For the first, utilities (sections 1, 6, and 8), this is
   generally structured as follows:
   .Bd -literal -offset indent
   \&.Nm foo
   \&.Op Fl v
   \&.Op Fl o Ar file
   \&.Op Ar
   \&.Nm bar
   \&.Op Fl v
   \&.Op Fl o Ar file
   \&.Op Ar
 .Ed  .Ed
 .\" PARAGRAPH  
 .Pp  .Pp
 In-lines have \(>=0 scoped arguments.  For the second, function calls (sections 2, 3, 9):
 .Bd -literal -offset XXX  .Bd -literal -offset indent
 \&.Yy \(lB\-arg \(lBval...\(rB\(rB \(lBargs...\(rB  \&.Vt extern const char *global;
   \&.In header.h
 \&.Yy \(lB\-arg \(lBval...\(rB\(rB arg0 arg1 argN  \&.Ft "char *"
   \&.Fn foo "const char *src"
   \&.Ft "char *"
   \&.Fn bar "const char *src"
 .Ed  .Ed
 .\"  .Pp
 .Sh MACROS  And for the third, configurations (section 4):
 This section contains a complete list of all  .Bd -literal -offset indent
 .Nm  \&.Cd \*qit* at isa? port 0x2e\*q
 macros, arranged ontologically.  A  \&.Cd \*qit* at isa? port 0x4e\*q
 .Qq callable  .Ed
 macro is invoked subsequent to the initial macro-line macro.  A  .Pp
 .Qq parsable  Manuals not in these sections generally don't need a
 macro may be followed by further (ostensibly callable) macros.  .Em SYNOPSIS .
 .\" SUB-SECTION  .Pp
   Some macros are displayed differently in the
   .Em SYNOPSIS
   section, particularly
   .Sx \&Nm ,
   .Sx \&Cd ,
   .Sx \&Fd ,
   .Sx \&Fn ,
   .Sx \&Fo ,
   .Sx \&In ,
   .Sx \&Vt ,
   and
   .Sx \&Ft .
   All of these macros are output on their own line.
   If two such dissimilar macros are pair-wise invoked (except for
   .Sx \&Ft
   before
   .Sx \&Fo
   or
   .Sx \&Fn ) ,
   they are separated by a vertical space, unless in the case of
   .Sx \&Fo ,
   .Sx \&Fn ,
   and
   .Sx \&Ft ,
   which are always separated by vertical space.
   .Pp
   When text and macros following an
   .Sx \&Nm
   macro starting an input line span multiple output lines,
   all output lines but the first will be indented to align
   with the text immediately following the
   .Sx \&Nm
   macro, up to the next
   .Sx \&Nm ,
   .Sx \&Sx ,
   or
   .Sx \&Ss
   macro or the end of an enclosing block, whichever comes first.
   .It Em DESCRIPTION
   This expands upon the brief, one-line description in
   .Em NAME .
   It usually contains a break-down of the options (if documenting a
   command), such as:
   .Bd -literal -offset indent
   The arguments are as follows:
   \&.Bl \-tag \-width Ds
   \&.It Fl v
   Print verbose information.
   \&.El
   .Ed
   .Pp
   Manuals not documenting a command won't include the above fragment.
   .It Em IMPLEMENTATION NOTES
   Implementation-specific notes should be kept here.
   This is useful when implementing standard functions that may have side
   effects or notable algorithmic implications.
   .It Em RETURN VALUES
   This section is the dual of
   .Em EXIT STATUS ,
   which is used for commands.
   It documents the return values of functions in sections 2, 3, and 9.
   .Pp
   See
   .Sx \&Rv .
   .It Em ENVIRONMENT
   Documents any usages of environment variables, e.g.,
   .Xr environ 7 .
   .Pp
   See
   .Sx \&Ev .
   .It Em FILES
   Documents files used.
   It's helpful to document both the file and a short description of how
   the file is used (created, modified, etc.).
   .Pp
   See
   .Sx \&Pa .
   .It Em EXIT STATUS
   Command exit status for section 1, 6, and 8 manuals.
   This section is the dual of
   .Em RETURN VALUES ,
   which is used for functions.
   Historically, this information was described in
   .Em DIAGNOSTICS ,
   a practise that is now discouraged.
   .Pp
   See
   .Sx \&Ex .
   .It Em EXAMPLES
   Example usages.
   This often contains snippets of well-formed, well-tested invocations.
   Make doubly sure that your examples work properly!
   .It Em DIAGNOSTICS
   Documents error conditions.
   This is most useful in section 4 manuals.
   Historically, this section was used in place of
   .Em EXIT STATUS
   for manuals in sections 1, 6, and 8; however, this practise is
   discouraged.
   .Pp
   See
   .Sx \&Bl
   .Fl diag .
   .It Em ERRORS
   Documents error handling in sections 2, 3, and 9.
   .Pp
   See
   .Sx \&Er .
   .It Em SEE ALSO
   References other manuals with related topics.
   This section should exist for most manuals.
   Cross-references should conventionally be ordered first by section, then
   alphabetically.
   .Pp
   See
   .Sx \&Xr .
   .It Em STANDARDS
   References any standards implemented or used.
   If not adhering to any standards, the
   .Em HISTORY
   section should be used instead.
   .Pp
   See
   .Sx \&St .
   .It Em HISTORY
   The history of any manual without a
   .Em STANDARDS
   section should be described in this section.
   .It Em AUTHORS
   Credits to authors, if applicable, should appear in this section.
   Authors should generally be noted by both name and an e-mail address.
   .Pp
   See
   .Sx \&An .
   .It Em CAVEATS
   Explanations of common misuses and misunderstandings should be explained
   in this section.
   .It Em BUGS
   Extant bugs should be described in this section.
   .It Em SECURITY CONSIDERATIONS
   Documents any security precautions that operators should consider.
   .El
   .Sh MACRO SYNTAX
   Macros are one to three three characters in length and begin with a
   control character ,
   .Sq \&. ,
   at the beginning of the line.
   An arbitrary amount of whitespace may sit between the control character
   and the macro name.
   Thus, the following are equivalent:
   .Bd -literal -offset indent
   \&.Pp
   \&.\ \ \ \&Pp
   .Ed
   .Pp
   The syntax of a macro depends on its classification.
   In this section,
   .Sq \-arg
   refers to macro arguments, which may be followed by zero or more
   .Sq parm
   parameters;
   .Sq \&Yo
   opens the scope of a macro; and if specified,
   .Sq \&Yc
   closes it out.
   .Pp
   The
   .Em Callable
   column indicates that the macro may be called subsequent to the initial
   line-macro.
   If a macro is not callable, then its invocation after the initial line
   macro is interpreted as opaque text, such that
   .Sq \&.Fl \&Sh
   produces
   .Sq Fl \&Sh .
   .Pp
   The
   .Em Parsable
   column indicates whether the macro may be followed by further
   (ostensibly callable) macros.
   If a macro is not parsable, subsequent macro invocations on the line
   will be interpreted as opaque text.
   .Pp
   The
   .Em Scope
   column, if applicable, describes closure rules.
   .Ss Block full-explicit
   Multi-line scope closed by an explicit closing macro.
   All macros contains bodies; only
   .Sx \&Bf
   contains a head.
   .Bd -literal -offset indent
   \&.Yo \(lB\-arg \(lBparm...\(rB\(rB \(lBhead...\(rB
   \(lBbody...\(rB
   \&.Yc
   .Ed
   .Pp
   .Bl -column -compact -offset indent "MacroX" "CallableX" "ParsableX" "closed by XXX"
   .It Em Macro Ta Em Callable Ta Em Parsable Ta Em Scope
   .It Sx \&Bd  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Ed
   .It Sx \&Bf  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Ef
   .It Sx \&Bk  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Ek
   .It Sx \&Bl  Ta    \&No     Ta    \&No     Ta    closed by Sx \&El
   .It Sx \&Ed  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Bd
   .It Sx \&Ef  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Bf
   .It Sx \&Ek  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Bk
   .It Sx \&El  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Bl
   .El
 .Ss Block full-implicit  .Ss Block full-implicit
 The head of these macros follows invocation; the body is the content of  Multi-line scope closed by end-of-file or implicitly by another macro.
 subsequent lines prior to closure.  None of these macros have tails;  All macros have bodies; some
 some  
 .Po  .Po
 .Sq \&.It \-bullet ,  .Sx \&It Fl bullet ,
 .Sq \-hyphen ,  .Fl hyphen ,
 .Sq \-dash ,  .Fl dash ,
 .Sq \-enum ,  .Fl enum ,
 .Sq \-item  .Fl item
 .Pc  .Pc
 don't have heads.  don't have heads; only one
   .Po
   .Sx \&It Fl column
   .Pc
   has multiple heads.
   .Bd -literal -offset indent
   \&.Yo \(lB\-arg \(lBparm...\(rB\(rB \(lBhead... \(lBTa head...\(rB\(rB
   \(lBbody...\(rB
   .Ed
 .Pp  .Pp
 .Bl -column "MacroX" "CallableX" "ParsableX" "Closing" -compact -offset XXXX  .Bl -column -compact -offset indent "MacroX" "CallableX" "ParsableX" "closed by XXXXXXXXXXX"
 .It Em Macro Ta Em Callable Ta Em Parsable Ta Em Closing  .It Em Macro Ta Em Callable Ta Em Parsable Ta Em Scope
 .It \&.Sh    Ta    \&No    Ta    \&No    Ta    \&.Sh  .It Sx \&It  Ta    \&No     Ta    Yes      Ta    closed by Sx \&It , Sx \&El
 .It \&.Ss    Ta    \&No    Ta    \&No    Ta    \&.Sh, \&.Ss  .It Sx \&Nd  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Sh
 .It \&.It    Ta    \&No    Ta    Yes     Ta    \&.It, \&.El  .It Sx \&Nm  Ta    \&No     Ta  Yes Ta closed by Sx \&Nm , Sx \&Sh , Sx \&Ss
   .It Sx \&Sh  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Sh
   .It Sx \&Ss  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Sh , Sx \&Ss
 .El  .El
 .\" SUB-SECTION  
 .Ss Block full-explicit  
 None of these macros are callable or parsed.  The last column indicates  
 the explicit scope rules.  All contains bodies, some may contain heads  
 .Pq So \&Bf Sc .  
 .Pp  .Pp
 .Bl -column "MacroX" "CallableX" "ParsableX" "closed by XXX" -compact -offset XXXX  Note that the
   .Sx \&Nm
   macro is a
   .Sx Block full-implicit
   macro only when invoked as the first macro
   in a
   .Em SYNOPSIS
   section line, else it is
   .Sx In-line .
   .Ss Block partial-explicit
   Like block full-explicit, but also with single-line scope.
   Each has at least a body and, in limited circumstances, a head
   .Po
   .Sx \&Fo ,
   .Sx \&Eo
   .Pc
   and/or tail
   .Pq Sx \&Ec .
   .Bd -literal -offset indent
   \&.Yo \(lB\-arg \(lBparm...\(rB\(rB \(lBhead...\(rB
   \(lBbody...\(rB
   \&.Yc \(lBtail...\(rB
   
   \&.Yo \(lB\-arg \(lBparm...\(rB\(rB \(lBhead...\(rB \
   \(lBbody...\(rB \&Yc \(lBtail...\(rB
   .Ed
   .Pp
   .Bl -column "MacroX" "CallableX" "ParsableX" "closed by XXXX" -compact -offset indent
 .It Em Macro Ta Em Callable Ta Em Parsable Ta Em Scope  .It Em Macro Ta Em Callable Ta Em Parsable Ta Em Scope
 .It \&.Bd    Ta    \&No    Ta    \&No    Ta    closed by \&.Ed  .It Sx \&Ac  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Ao
 .It \&.Ed    Ta    \&No    Ta    \&No    Ta    opened by \&.Bd  .It Sx \&Ao  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Ac
 .It \&.Bl    Ta    \&No    Ta    \&No    Ta    closed by \&.El  .It Sx \&Bc  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Bo
 .It \&.El    Ta    \&No    Ta    \&No    Ta    opened by \&.Bl  .It Sx \&Bo  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Bc
 .It \&.Bf    Ta    \&No    Ta    \&No    Ta    closed by \&.Ef  .It Sx \&Brc Ta    Yes      Ta    Yes      Ta    opened by Sx \&Bro
 .It \&.Ef    Ta    \&No    Ta    \&No    Ta    opened by \&.Bf  .It Sx \&Bro Ta    Yes      Ta    Yes      Ta    closed by Sx \&Brc
 .It \&.Bk    Ta    \&No    Ta    \&No    Ta    closed by \&.Ek  .It Sx \&Dc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Do
 .It \&.Ek    Ta    \&No    Ta    \&No    Ta    opened by \&.Bk  .It Sx \&Do  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Dc
   .It Sx \&Ec  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Eo
   .It Sx \&Eo  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Ec
   .It Sx \&Fc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Fo
   .It Sx \&Fo  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Fc
   .It Sx \&Oc  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Oo
   .It Sx \&Oo  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Oc
   .It Sx \&Pc  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Po
   .It Sx \&Po  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Pc
   .It Sx \&Qc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Oo
   .It Sx \&Qo  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Oc
   .It Sx \&Re  Ta    \&No     Ta    \&No     Ta    opened by Sx \&Rs
   .It Sx \&Rs  Ta    \&No     Ta    \&No     Ta    closed by Sx \&Re
   .It Sx \&Sc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&So
   .It Sx \&So  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Sc
   .It Sx \&Xc  Ta    Yes      Ta    Yes      Ta    opened by Sx \&Xo
   .It Sx \&Xo  Ta    Yes      Ta    Yes      Ta    closed by Sx \&Xc
 .El  .El
 .\" SUB-SECTION  
 .Ss Block partial-implicit  .Ss Block partial-implicit
 All of these are callable and parsed for further macros.  Their scopes  Like block full-implicit, but with single-line scope closed by
 close at the invocation's end-of-line.  .Sx Reserved Characters
   or end of line.
   .Bd -literal -offset indent
   \&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBbody...\(rB \(lBres...\(rB
   .Ed
 .Pp  .Pp
 .Bl -column "MacroX" "CallableX" "ParsableX" -compact -offset XXXX  .Bl -column "MacroX" "CallableX" "ParsableX" -compact -offset indent
 .It Em Macro Ta Em Callable Ta Em Parsable  .It Em Macro Ta Em Callable Ta Em Parsable
 .It \&.Aq    Ta    Yes   Ta    Yes  .It Sx \&Aq  Ta    Yes      Ta    Yes
 .It \&.Op    Ta    Yes   Ta    Yes  .It Sx \&Bq  Ta    Yes      Ta    Yes
 .It \&.Bq    Ta    Yes   Ta    Yes  .It Sx \&Brq Ta    Yes      Ta    Yes
 .It \&.Dq    Ta    Yes   Ta    Yes  .It Sx \&D1  Ta    \&No     Ta    \&Yes
 .It \&.Pq    Ta    Yes   Ta    Yes  .It Sx \&Dl  Ta    \&No     Ta    Yes
 .It \&.Qq    Ta    Yes   Ta    Yes  .It Sx \&Dq  Ta    Yes      Ta    Yes
 .It \&.Sq    Ta    Yes   Ta    Yes  .It Sx \&Op  Ta    Yes      Ta    Yes
 .It \&.Brq   Ta    Yes   Ta    Yes  .It Sx \&Pq  Ta    Yes      Ta    Yes
 .It \&.D1    Ta    \&No  Ta    \&Yes  .It Sx \&Ql  Ta    Yes      Ta    Yes
 .It \&.Dl    Ta    \&No  Ta    Yes  .It Sx \&Qq  Ta    Yes      Ta    Yes
 .It \&.Ql    Ta    Yes   Ta    Yes  .It Sx \&Sq  Ta    Yes      Ta    Yes
   .It Sx \&Vt  Ta    Yes      Ta    Yes
 .El  .El
 .\" PARAGRAPH  
 .Pp  .Pp
   Note that the
   .Sx \&Vt
   macro is a
   .Sx Block partial-implicit
   only when invoked as the first macro
   in a
   .Em SYNOPSIS
   section line, else it is
   .Sx In-line .
   .Ss In-line
   Closed by
   .Sx Reserved Characters ,
   end of line, fixed argument lengths, and/or subsequent macros.
   In-line macros have only text children.
   If a number (or inequality) of arguments is
   .Pq n ,
   then the macro accepts an arbitrary number of arguments.
   .Bd -literal -offset indent
   \&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBargs...\(rB \(lbres...\(rb
   
   \&.Yo \(lB\-arg \(lBval...\(rB\(rB \(lBargs...\(rB Yc...
   
   \&.Yo \(lB\-arg \(lBval...\(rB\(rB arg0 arg1 argN
   .Ed
   .Pp
   .Bl -column "MacroX" "CallableX" "ParsableX" "Arguments" -compact -offset indent
   .It Em Macro Ta Em Callable Ta Em Parsable Ta Em Arguments
   .It Sx \&%A  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%B  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%C  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%D  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%I  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%J  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%N  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%O  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%P  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%Q  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%R  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%T  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%U  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&%V  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&Ad  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&An  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Ap  Ta    Yes      Ta    Yes      Ta    0
   .It Sx \&Ar  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&At  Ta    Yes      Ta    Yes      Ta    1
   .It Sx \&Bsx Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Bt  Ta    \&No     Ta    \&No     Ta    0
   .It Sx \&Bx  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Cd  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Cm  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Db  Ta    \&No     Ta    \&No     Ta    1
   .It Sx \&Dd  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&Dt  Ta    \&No     Ta    \&No     Ta    n
   .It Sx \&Dv  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Dx  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Em  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&En  Ta    \&No     Ta    \&No     Ta    0
   .It Sx \&Er  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Es  Ta    \&No     Ta    \&No     Ta    0
   .It Sx \&Ev  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Ex  Ta    \&No     Ta    \&No     Ta    n
   .It Sx \&Fa  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Fd  Ta    \&No     Ta    \&No     Ta    >0
   .It Sx \&Fl  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Fn  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Fr  Ta    \&No     Ta    \&No     Ta    n
   .It Sx \&Ft  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Fx  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Hf  Ta    \&No     Ta    \&No     Ta    n
   .It Sx \&Ic  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&In  Ta    \&No     Ta    \&No     Ta    n
   .It Sx \&Lb  Ta    \&No     Ta    \&No     Ta    1
   .It Sx \&Li  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Lk  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Lp  Ta    \&No     Ta    \&No     Ta    0
   .It Sx \&Ms  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Mt  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Nm  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&No  Ta    Yes      Ta    Yes      Ta    0
   .It Sx \&Ns  Ta    Yes      Ta    Yes      Ta    0
   .It Sx \&Nx  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Os  Ta    \&No     Ta    \&No     Ta    n
   .It Sx \&Ot  Ta    \&No     Ta    \&No     Ta    n
   .It Sx \&Ox  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Pa  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Pf  Ta    Yes      Ta    Yes      Ta    1
   .It Sx \&Pp  Ta    \&No     Ta    \&No     Ta    0
   .It Sx \&Rv  Ta    \&No     Ta    \&No     Ta    n
   .It Sx \&Sm  Ta    \&No     Ta    \&No     Ta    1
   .It Sx \&St  Ta    \&No     Ta    Yes      Ta    1
   .It Sx \&Sx  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Sy  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Tn  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Ud  Ta    \&No     Ta    \&No     Ta    0
   .It Sx \&Ux  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Va  Ta    Yes      Ta    Yes      Ta    n
   .It Sx \&Vt  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&Xr  Ta    Yes      Ta    Yes      Ta    >0
   .It Sx \&br  Ta    \&No     Ta    \&No     Ta    0
   .It Sx \&sp  Ta    \&No     Ta    \&No     Ta    1
   .El
   .Sh REFERENCE
   This section is a canonical reference of all macros, arranged
   alphabetically.
   For the scoping of individual macros, see
   .Sx MACRO SYNTAX .
   .Ss \&%A
   Author name of an
   .Sx \&Rs
   block.
   Multiple authors should each be accorded their own
   .Sx \%%A
   line.
   Author names should be ordered with full or abbreviated forename(s)
   first, then full surname.
   .Ss \&%B
   Book title of an
   .Sx \&Rs
   block.
   This macro may also be used in a non-bibliographic context when
   referring to book titles.
   .Ss \&%C
   Publication city or location of an
   .Sx \&Rs
   block.
   .Pp
   .Em Remarks :
   this macro is not implemented in
   .Xr groff 1 .
   .Ss \&%D
   Publication date of an
   .Sx \&Rs
   block.
   This should follow the reduced or canonical form syntax described in
   .Sx Dates .
   .Ss \&%I
   Publisher or issuer name of an
   .Sx \&Rs
   block.
   .Ss \&%J
   Journal name of an
   .Sx \&Rs
   block.
   .Ss \&%N
   Issue number (usually for journals) of an
   .Sx \&Rs
   block.
   .Ss \&%O
   Optional information of an
   .Sx \&Rs
   block.
   .Ss \&%P
   Book or journal page number of an
   .Sx \&Rs
   block.
   .Ss \&%Q
   Institutional author (school, government, etc.) of an
   .Sx \&Rs
   block.
   Multiple institutional authors should each be accorded their own
   .Sx \&%Q
   line.
   .Ss \&%R
   Technical report name of an
   .Sx \&Rs
   block.
   .Ss \&%T
   Article title of an
   .Sx \&Rs
   block.
   This macro may also be used in a non-bibliographical context when
   referring to article titles.
   .Ss \&%U
   URI of reference document.
   .Ss \&%V
   Volume number of an
   .Sx \&Rs
   block.
   .Ss \&Ac
   Closes an
   .Sx \&Ao
   block.
   Does not have any tail arguments.
   .Ss \&Ad
   Address construct: usually in the context of an computational address in
   memory, not a physical (post) address.
   .Pp
   Examples:
   .D1 \&.Ad [0,$]
   .D1 \&.Ad 0x00000000
   .Ss \&An
   Author name.
   This macro may alternatively accepts the following arguments, although
   these may not be specified along with a parameter:
   .Pp
   .Bl -tag -width "-nosplitX" -offset indent -compact
   .It Fl split
   Renders a line break before each author listing.
   .It Fl nosplit
   The opposite of
   .Fl split .
   .El
   .Pp
   In the
   .Em AUTHORS
   section, the default is not to split the first author
   listing, but all subsequent author listings, whether or not they're
   interspersed by other macros or text, are split.
   Thus, specifying
   .Fl split
   will cause the first listing also to be split.
   If not in the
   .Em AUTHORS
   section, the default is not to split.
   .Pp
   Examples:
   .D1 \&.An -nosplit
   .D1 \&.An J. D. Ullman .
   .Pp
   .Em Remarks :
   the effects of
   .Fl split
   or
   .Fl nosplit
   are re-set when entering the
   .Em AUTHORS
   section, so if one specifies
   .Sx \&An Fl nosplit
   in the general document body, it must be re-specified in the
   .Em AUTHORS
   section.
   .Ss \&Ao
   Begins a block enclosed by angled brackets.
   Does not have any head arguments.
   .Pp
   Examples:
   .D1 \&.Fl -key= \&Ns \&Ao \&Ar val \&Ac
   .Pp
   See also
   .Sx \&Aq .
   .Ss \&Ap
   Inserts an apostrophe without any surrounding whitespace.
   This is generally used as a grammatical device when referring to the verb
   form of a function.
   .Pp
   Examples:
   .D1 \&.Fn execve \&Ap d
   .Ss \&Aq
   Encloses its arguments in angled brackets.
   .Pp
   Examples:
   .D1 \&.Fl -key= \&Ns \&Aq \&Ar val
   .Pp
   .Em Remarks :
   this macro is often abused for rendering URIs, which should instead use
   .Sx \&Lk
   or
   .Sx \&Mt ,
   or to note pre-processor
   .Dq Li #include
   statements, which should use
   .Sx \&In .
   .Pp
   See also
   .Sx \&Ao .
   .Ss \&Ar
   Command arguments.
   If an argument is not provided, the string
   .Dq file ...
   is used as a default.
   .Pp
   Examples:
   .D1 \&.Fl o \&Ns \&Ar file1
   .D1 \&.Ar
   .D1 \&.Ar arg1 , arg2 .
   .Ss \&At
   Formats an AT&T version.
   Accepts at most one parameter:
   .Pp
   .Bl -tag -width "v[1-7] | 32vX" -offset indent -compact
   .It Cm v[1-7] | 32v
   A version of
   .At .
   .It Cm V[.[1-4]]?
   A system version of
   .At .
   .El
   .Pp
   Note that these parameters do not begin with a hyphen.
   .Pp
   Examples:
   .D1 \&.At
   .D1 \&.At V.1
   .Pp
   See also
   .Sx \&Bsx ,
   .Sx \&Bx ,
   .Sx \&Dx ,
   .Sx \&Fx ,
   .Sx \&Nx ,
   .Sx \&Ox ,
   and
   .Sx \&Ux .
   .Ss \&Bc
   Closes a
   .Sx \&Bo
   block.
   Does not have any tail arguments.
   .Ss \&Bd
   Begins a display block.
   Its syntax is as follows:
   .Bd -ragged -offset indent
   .Pf \. Sx \&Bd
   .Fl type
   .Op Fl offset Ar width
   .Op Fl compact
   .Ed
   .Pp
   A display is collection of macros or text which may be collectively
   offset or justified in a manner different from that
   of the enclosing context.
   By default, the block is preceded by a vertical space.
   .Pp
   Each display is associated with a type, which must be one of the
   following arguments:
   .Bl -tag -width 12n -offset indent
   .It Fl ragged
   Only left-justify the block.
   .It Fl unfilled
   Do not justify the block at all.
   .It Fl filled
   Left- and right-justify the block.
   .It Fl literal
   Alias for
   .Fl unfilled .
   .It Fl centered
   Centre-justify each line.
   .El
   .Pp
   The type must be provided first.
   Secondary arguments are as follows:
   .Bl -tag -width 12n -offset indent
   .It Fl offset Ar val
   Offset by the value of
   .Ar val ,
   which is interpreted as one of the following, specified in order:
   .Bl -item
   .It
   As one of the pre-defined strings
   .Ar indent ,
   the width of standard indentation;
   .Ar indent-two ,
   twice
   .Ar indent ;
   .Ar left ,
   which has no effect;
   .Ar right ,
   which justifies to the right margin; and
   .Ar center ,
   which aligns around an imagined centre axis.
   .It
   As a precalculated width for a named macro.
   The most popular is the imaginary macro
   .Ar \&Ds ,
   which resolves to
   .Ar 6n .
   .It
   As a scaling unit following the syntax described in
   .Sx Scaling Widths .
   .It
   As the calculated string length of the opaque string.
   .El
   .Pp
   If not provided an argument, it will be ignored.
   .It Fl compact
   Do not assert a vertical space before the block.
   .El
   .Pp
   Examples:
   .Bd -literal -offset indent
   \&.Bd \-unfilled \-offset two-indent \-compact
      Hello       world.
   \&.Ed
   .Ed
   .Pp
   See also
   .Sx \&D1
   and
   .Sx \&Dl .
   .Ss \&Bf
   Change the font mode for a scoped block of text.
   Its syntax is as follows:
   .Bd -ragged -offset indent
   .Pf \. Sx \&Bf
   .Oo
   .Fl emphasis | literal | symbolic |
   .Cm \&Em | \&Li | \&Sy
   .Oc
   .Ed
   .Pp
 The  The
 .Sq \&.Op  .Fl emphasis
 may be broken by  and
 .Sq \&.Oc  .Cm \&Em
 as in the following example:  argument are equivalent, as are
 .Bd -literal -offset XXXX  .Fl symbolic
 \&.Oo  and
 \&.Op Fl a Oc  .Cm \&Sy,
   and
   .Fl literal
   and
   .Cm \&Li .
   Without an argument, this macro does nothing.
   The font mode continues until broken by a new font mode in a nested
   scope or
   .Sx \&Ef
   is encountered.
   .Pp
   See also
   .Sx \&Li ,
   .Sx \&Ef ,
   and
   .Sx \&Sy .
   .Ss \&Bk
   Begins a collection of macros or text not breaking the line.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Bk Fl words
   .Pp
   Subsequent arguments are ignored.
   The
   .Fl words
   argument is required.
   .Pp
   Each line within a keep block is kept intact, so the following example
   will not break within each
   .Sx \&Op
   macro line:
   .Bd -literal -offset indent
   \&.Bk \-words
   \&.Op Fl f Ar flags
   \&.Op Fl o Ar output
   \&.Ek
 .Ed  .Ed
 .Pp  .Pp
 In the above example, the scope of  Be careful in using over-long lines within a keep block!
 .Sq \&.Op  Doing so will clobber the right margin.
 is technically broken by  .Ss \&Bl
 .Sq \&.Oc ,  Begins a list composed of one or more list entries.
 however, due to the overwhelming existence of this sequence, it's  Its syntax is as follows:
 allowed.  .Bd -ragged -offset indent
 .\" SUB-SECTION  .Pf \. Sx \&Bl
 .Ss Block partial-explicit  .Fl type
 Each of these contains at least a body and, in limited circumstances, a  .Op Fl width Ar val
 head  .Op Fl offset Ar val
 .Pq So \&.Fo Sc , So \&.Eo Sc  .Op Fl compact
 and/or tail  .Op HEAD ...
 .Pq So \&.Ec Sc .  .Ed
 .Pp  .Pp
 .Bl -column "MacroX" "CallableX" "ParsableX" "closed by XXXX" -compact -offset XXXX  A list is associated with a type, which is a required argument.
 .It Em Macro Ta Em Callable Ta Em Parsable Ta Em Scope  Other arguments are
 .It \&.Ao    Ta    Yes   Ta    Yes    Ta    closed by \&.Ac  .Fl width ,
 .It \&.Ac    Ta    Yes   Ta    Yes    Ta    opened by \&.Ao  defined per-type as accepting a literal or
 .It \&.Bc    Ta    Yes   Ta    Yes    Ta    closed by \&.Bo  .Sx Scaling Widths
 .It \&.Bo    Ta    Yes   Ta    Yes    Ta    opened by \&.Bc  value;
 .It \&.Pc    Ta    Yes   Ta    Yes    Ta    closed by \&.Po  .Fl offset ,
 .It \&.Po    Ta    Yes   Ta    Yes    Ta    opened by \&.Pc  also accepting a literal or
 .It \&.Do    Ta    Yes   Ta    Yes    Ta    closed by \&.Dc  .Sx Scaling Widths
 .It \&.Dc    Ta    Yes   Ta    Yes    Ta    opened by \&.Do  value setting the list's global offset; and
 .It \&.Xo    Ta    Yes   Ta    Yes    Ta    closed by \&.Xc  .Fl compact ,
 .It \&.Xc    Ta    Yes   Ta    Yes    Ta    opened by \&.Xo  suppressing the default vertical space printed before each list entry.
 .It \&.Bro   Ta    Yes   Ta    Yes    Ta    closed by \&.Brc  A list entry is specified by the
 .It \&.Brc   Ta    Yes   Ta    Yes    Ta    opened by \&.Bro  .Sx \&It
 .It \&.Oc    Ta    Yes   Ta    Yes    Ta    closed by \&.Oo  macro, which consists of a head and optional body (depending on the list
 .It \&.Oo    Ta    Yes   Ta    Yes    Ta    opened by \&.Oc  type).
 .It \&.So    Ta    Yes   Ta    Yes    Ta    closed by \&.Sc  A list must specify one of the following list types:
 .It \&.Sc    Ta    Yes   Ta    Yes    Ta    opened by \&.So  .Bl -tag -width 12n -offset indent
 .It \&.Fc    Ta    Yes   Ta    Yes    Ta    opened by \&.Fo  .It Fl bullet
 .It \&.Fo    Ta    \&No  Ta    \&No   Ta    closed by \&.Fc  A list offset by a bullet.
 .It \&.Ec    Ta    Yes   Ta    Yes    Ta    opened by \&.Eo  The head of list entries must be empty.
 .It \&.Eo    Ta    Yes   Ta    Yes    Ta    closed by \&.Ec  List entry bodies are positioned after the bullet.
 .It \&.Qc    Ta    Yes   Ta    Yes    Ta    opened by \&.Oo  The
 .It \&.Qo    Ta    Yes   Ta    Yes    Ta    closed by \&.Oc  .Fl width
 .It \&.Re    Ta    \&No  Ta    \&No   Ta    opened by \&.Rs  argument varies the width of list bodies' left-margins.
 .It \&.Rs    Ta    \&No  Ta    \&No   Ta    closed by \&.Re  .It Fl column
   A columnated list.
   The
   .Fl width
   argument has no effect.
   The number of columns is specified as parameters to the
   .Sx \&Bl
   macro.
   These dictate the width of columns either as
   .Sx Scaling Widths
   or literal text.
   If the initial macro of a
   .Fl column
   list is not an
   .Sx \&It ,
   an
   .Sx \&It
   context spanning each line is implied until an
   .Sx \&It
   line macro is encountered, at which point list bodies are interpreted as
   described in the
   .Sx \&It
   documentation.
   .It Fl dash
   A list offset by a dash (hyphen).
   The head of list entries must be empty.
   List entry bodies are positioned past the dash.
   The
   .Fl width
   argument varies the width of list bodies' left-margins.
   .It Fl diag
   Like
   .Fl inset ,
   but with additional formatting to the head.
   The
   .Fl width
   argument varies the width of list bodies' left-margins.
   .It Fl enum
   An enumerated list offset by the enumeration from 1.
   The head of list entries must be empty.
   List entry bodies are positioned after the enumeration.
   The
   .Fl width
   argument varies the width of list bodies' left-margins.
   .It Fl hang
   Like
   .Fl tag ,
   but instead of list bodies positioned after the head, they trail the
   head text.
   The
   .Fl width
   argument varies the width of list bodies' left-margins.
   .It Fl hyphen
   Synonym for
   .Fl dash .
   .It Fl inset
   List bodies follow the list head.
   The
   .Fl width
   argument is ignored.
   .It Fl item
   This produces blocks of text.
   The head of list entries must be empty.
   The
   .Fl width
   argument is ignored.
   .It Fl ohang
   List bodies are positioned on the line following the head.
   The
   .Fl width
   argument is ignored.
   .It Fl tag
   A list offset by list entry heads.
   List entry bodies are positioned after the head as specified by the
   .Fl width
   argument.
 .El  .El
 .\" SUB-SECTION  
 .Ss In-line  
 In-line macros have only text children.  If a number (or inequality) of  
 arguments is  
 .Pq n ,  
 then the macro accepts an arbitrary number of arguments.  
 .Pp  .Pp
 .Bl -column "MacroX" "CallableX" "ParsableX" "Arguments" -compact -offset XXXX  See also
 .It Em Macro Ta Em Callable Ta Em Parsable Ta Em Arguments  .Sx \&It .
 .It \&.Dd    Ta    \&No  Ta    \&No    Ta    >0  .Ss \&Bo
 .It \&.Dt    Ta    \&No  Ta    \&No    Ta    n  Begins a block enclosed by square brackets.
 .It \&.Os    Ta    \&No  Ta    \&No    Ta    n  Does not have any head arguments.
 .It \&.Pp    Ta    \&No  Ta    \&No    Ta    0  .Pp
 .It \&.Ad    Ta    Yes   Ta    Yes     Ta    n  Examples:
 .It \&.An    Ta    \&No  Ta    Yes     Ta    n  .Bd -literal -offset indent -compact
 .It \&.Ar    Ta    Yes   Ta    Yes     Ta    n  \&.Bo 1 ,
 .It \&.Cd    Ta    Yes   Ta    \&No    Ta    >0  \&.Dv BUFSIZ \&Bc
 .It \&.Cm    Ta    Yes   Ta    Yes     Ta    n  .Ed
 .It \&.Dv    Ta    Yes   Ta    Yes     Ta    n  .Pp
 .It \&.Er    Ta    Yes   Ta    Yes     Ta    >0  See also
 .It \&.Ev    Ta    Yes   Ta    Yes     Ta    n  .Sx \&Bq .
 .It \&.Ex    Ta    \&No  Ta    \&No    Ta    0  .Ss \&Bq
 .It \&.Fa    Ta    Yes   Ta    Yes     Ta    n  Encloses its arguments in square brackets.
 .It \&.Fd    Ta    \&No  Ta    \&No    Ta    >0  .Pp
 .It \&.Fl    Ta    Yes   Ta    Yes     Ta    n  Examples:
 .It \&.Fn    Ta    Yes   Ta    Yes     Ta    >0  .D1 \&.Bq 1 , \&Dv BUFSIZ
 .It \&.Ft    Ta    \&No  Ta    Yes     Ta    n  .Pp
 .It \&.Ic    Ta    Yes   Ta    Yes     Ta    >0  .Em Remarks :
 .It \&.In    Ta    \&No  Ta    \&No    Ta    n  this macro is sometimes abused to emulate optional arguments for
 .It \&.Li    Ta    Yes   Ta    Yes     Ta    n  commands; the correct macros to use for this purpose are
 .It \&.Nd    Ta    \&No  Ta    \&No    Ta    n  .Sx \&Op ,
 .It \&.Nm    Ta    Yes   Ta    Yes     Ta    n  .Sx \&Oo ,
 .It \&.Ot    Ta    \&No  Ta    \&No    Ta    n  and
 .It \&.Pa    Ta    Yes   Ta    Yes     Ta    n  .Sx \&Oc .
 .It \&.Rv    Ta    \&No  Ta    \&No    Ta    0  .Pp
 .It \&.St    Ta    \&No  Ta    Yes     Ta    1  See also
 .It \&.Va    Ta    Yes   Ta    Yes     Ta    n  .Sx \&Bo .
 .It \&.Vt    Ta    Yes   Ta    Yes     Ta    >0  .Ss \&Brc
 .It \&.Xr    Ta    Yes   Ta    Yes     Ta    >0, <3  Closes a
 .It \&.%A    Ta    \&No  Ta    \&No    Ta    >0  .Sx \&Bro
 .It \&.%B    Ta    \&No  Ta    \&No    Ta    >0  block.
 .It \&.%C    Ta    \&No  Ta    \&No    Ta    >0  Does not have any tail arguments.
 .It \&.%D    Ta    \&No  Ta    \&No    Ta    >0  .Ss \&Bro
 .It \&.%I    Ta    \&No  Ta    \&No    Ta    >0  Begins a block enclosed by curly braces.
 .It \&.%J    Ta    \&No  Ta    \&No    Ta    >0  Does not have any head arguments.
 .It \&.%N    Ta    \&No  Ta    \&No    Ta    >0  .Pp
 .It \&.%O    Ta    \&No  Ta    \&No    Ta    >0  Examples:
 .It \&.%P    Ta    \&No  Ta    \&No    Ta    >0  .Bd -literal -offset indent -compact
 .It \&.%R    Ta    \&No  Ta    \&No    Ta    >0  \&.Bro 1 , ... ,
 .It \&.%T    Ta    \&No  Ta    \&No    Ta    >0  \&.Va n \&Brc
 .It \&.%V    Ta    \&No  Ta    \&No    Ta    >0  .Ed
 .It \&.At    Ta    Yes   Ta    Yes     Ta    1  .Pp
 .It \&.Bsx   Ta    Yes   Ta    Yes     Ta    n  See also
 .It \&.Bx    Ta    Yes   Ta    Yes     Ta    n  .Sx \&Brq .
 .It \&.Db    Ta    \&No  Ta    \&No    Ta    1  .Ss \&Brq
 .It \&.Em    Ta    Yes   Ta    Yes     Ta    >0  Encloses its arguments in curly braces.
 .It \&.Fx    Ta    Yes   Ta    Yes     Ta    n  .Pp
 .It \&.Ms    Ta    \&No  Ta    Yes     Ta    >0  Examples:
 .It \&.No    Ta    Yes   Ta    Yes     Ta    0  .D1 \&.Brq 1 , ... , \&Va n
 .It \&.Ns    Ta    Yes   Ta    Yes     Ta    0  .Pp
 .It \&.Nx    Ta    Yes   Ta    Yes     Ta    n  See also
 .It \&.Ox    Ta    Yes   Ta    Yes     Ta    n  .Sx \&Bro .
 .It \&.Pf    Ta    \&No  Ta    Yes     Ta    1  .Ss \&Bsx
 .It \&.Sm    Ta    \&No  Ta    \&No    Ta    1  Format the BSD/OS version provided as an argument, or a default value if
 .It \&.Sx    Ta    Yes   Ta    Yes     Ta    >0  no argument is provided.
 .It \&.Sy    Ta    Yes   Ta    Yes     Ta    >0  .Pp
 .It \&.Tn    Ta    Yes   Ta    Yes     Ta    >0  Examples:
 .It \&.Ux    Ta    Yes   Ta    Yes     Ta    n  .D1 \&.Bsx 1.0
 .It \&.Dx    Ta    Yes   Ta    Yes     Ta    n  .D1 \&.Bsx
 .It \&.Bt    Ta    \&No  Ta    \&No    Ta    0  .Pp
 .It \&.Hf    Ta    \&No  Ta    \&No    Ta    n  See also
 .It \&.Fr    Ta    \&No  Ta    \&No    Ta    n  .Sx \&At ,
 .It \&.Ud    Ta    \&No  Ta    \&No    Ta    0  .Sx \&Bx ,
 .It \&.Lb    Ta    \&No  Ta    \&No    Ta    1  .Sx \&Dx ,
 .It \&.Ap    Ta    Yes   Ta    Yes     Ta    0  .Sx \&Fx ,
 .It \&.Lp    Ta    \&No  Ta    \&No    Ta    0  .Sx \&Nx ,
 .It \&.Lk    Ta    \&No  Ta    Yes     Ta    >0  .Sx \&Ox ,
 .It \&.Mt    Ta    \&No  Ta    Yes     Ta    >0  and
 .It \&.Es    Ta    \&No  Ta    \&No    Ta    0  .Sx \&Ux .
 .It \&.En    Ta    \&No  Ta    \&No    Ta    0  .Ss \&Bt
   Prints
   .Dq is currently in beta test.
   .Ss \&Bx
   Format the BSD version provided as an argument, or a default value if no
   argument is provided.
   .Pp
   Examples:
   .D1 \&.Bx 4.4
   .D1 \&.Bx
   .Pp
   See also
   .Sx \&At ,
   .Sx \&Bsx ,
   .Sx \&Dx ,
   .Sx \&Fx ,
   .Sx \&Nx ,
   .Sx \&Ox ,
   and
   .Sx \&Ux .
   .Ss \&Cd
   Configuration declaration.
   This denotes strings accepted by
   .Xr config 8 .
   .Pp
   Examples:
   .D1 \&.Cd device le0 at scode?
   .Pp
   .Em Remarks :
   this macro is commonly abused by using quoted literals to retain
   whitespace and align consecutive
   .Sx \&Cd
   declarations.
   This practise is discouraged.
   .Ss \&Cm
   Command modifiers.
   Useful when specifying configuration options or keys.
   .Pp
   Examples:
   .D1 \&.Cm ControlPath
   .D1 \&.Cm ControlMaster
   .Pp
   See also
   .Sx \&Fl .
   .Ss \&D1
   One-line indented display.
   This is formatted by the default rules and is useful for simple indented
   statements.
   It is followed by a newline.
   .Pp
   Examples:
   .D1 \&.D1 \&Fl abcdefgh
   .Pp
   See also
   .Sx \&Bd
   and
   .Sx \&Dl .
   .Ss \&Db
   Start a debugging context.
   This macro is parsed, but generally ignored.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Db Cm on | off
   .Ss \&Dc
   Closes a
   .Sx \&Do
   block.
   Does not have any tail arguments.
   .Ss \&Dd
   Document date.
   This is the mandatory first macro of any
   .Nm
   manual.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Dd Cm date
   .Pp
   The
   .Cm date
   field may be either
   .Ar $\&Mdocdate$ ,
   which signifies the current manual revision date dictated by
   .Xr cvs 1 ,
   or instead a valid canonical date as specified by
   .Sx Dates .
   If a date does not conform, the current date is used instead.
   .Pp
   Examples:
   .D1 \&.Dd $\&Mdocdate$
   .D1 \&.Dd $\&Mdocdate: July 21 2007$
   .D1 \&.Dd July 21, 2007
   .Pp
   See also
   .Sx \&Dt
   and
   .Sx \&Os .
   .Ss \&Dl
   One-line intended display.
   This is formatted as literal text and is useful for commands and
   invocations.
   It is followed by a newline.
   .Pp
   Examples:
   .D1 \&.Dl % mandoc mdoc.7 \e(ba less
   .Pp
   See also
   .Sx \&Bd
   and
   .Sx \&D1 .
   .Ss \&Do
   Begins a block enclosed by double quotes.
   Does not have any head arguments.
   .Pp
   Examples:
   .Bd -literal -offset indent -compact
   \&.Do
   April is the cruellest month
   \&.Dc
   \e(em T.S. Eliot
   .Ed
   .Pp
   See also
   .Sx \&Dq .
   .Ss \&Dq
   Encloses its arguments in
   .Dq typographic
   double-quotes.
   .Pp
   Examples:
   .Bd -literal -offset indent -compact
   \&.Dq April is the cruellest month
   \e(em T.S. Eliot
   .Ed
   .Pp
   See also
   .Sx \&Qq ,
   .Sx \&Sq ,
   and
   .Sx \&Do .
   .Ss \&Dt
   Document title.
   This is the mandatory second macro of any
   .Nm
   file.
   Its syntax is as follows:
   .Bd -ragged -offset indent
   .Pf \. Sx \&Dt
   .Oo
   .Cm title
   .Oo
   .Cm section
   .Op Cm volume | arch
   .Oc
   .Oc
   .Ed
   .Pp
   Its arguments are as follows:
   .Bl -tag -width Ds -offset Ds
   .It Cm title
   The document's title (name), defaulting to
   .Dq UNKNOWN
   if unspecified.
   It should be capitalised.
   .It Cm section
   The manual section.
   This may be one of
   .Ar 1
   .Pq utilities ,
   .Ar 2
   .Pq system calls ,
   .Ar 3
   .Pq libraries ,
   .Ar 3p
   .Pq Perl libraries ,
   .Ar 4
   .Pq devices ,
   .Ar 5
   .Pq file formats ,
   .Ar 6
   .Pq games ,
   .Ar 7
   .Pq miscellaneous ,
   .Ar 8
   .Pq system utilities ,
   .Ar 9
   .Pq kernel functions ,
   .Ar X11
   .Pq X Window System ,
   .Ar X11R6
   .Pq X Window System ,
   .Ar unass
   .Pq unassociated ,
   .Ar local
   .Pq local system ,
   .Ar draft
   .Pq draft manual ,
   or
   .Ar paper
   .Pq paper .
   It should correspond to the manual's filename suffix and defaults to
   .Dq 1
   if unspecified.
   .It Cm volume
   This overrides the volume inferred from
   .Ar section .
   This field is optional, and if specified, must be one of
   .Ar USD
   .Pq users' supplementary documents ,
   .Ar PS1
   .Pq programmers' supplementary documents ,
   .Ar AMD
   .Pq administrators' supplementary documents ,
   .Ar SMM
   .Pq system managers' manuals ,
   .Ar URM
   .Pq users' reference manuals ,
   .Ar PRM
   .Pq programmers' reference manuals ,
   .Ar KM
   .Pq kernel manuals ,
   .Ar IND
   .Pq master index ,
   .Ar MMI
   .Pq master index ,
   .Ar LOCAL
   .Pq local manuals ,
   .Ar LOC
   .Pq local manuals ,
   or
   .Ar CON
   .Pq contributed manuals .
   .It Cm arch
   This specifies a specific relevant architecture.
   If
   .Cm volume
   is not provided, it may be used in its place, else it may be used
   subsequent that.
   It, too, is optional.
   It must be one of
   .Ar alpha ,
   .Ar amd64 ,
   .Ar amiga ,
   .Ar arc ,
   .Ar arm ,
   .Ar armish ,
   .Ar aviion ,
   .Ar hp300 ,
   .Ar hppa ,
   .Ar hppa64 ,
   .Ar i386 ,
   .Ar landisk ,
   .Ar loongson ,
   .Ar luna88k ,
   .Ar mac68k ,
   .Ar macppc ,
   .Ar mvme68k ,
   .Ar mvme88k ,
   .Ar mvmeppc ,
   .Ar pmax ,
   .Ar sgi ,
   .Ar socppc ,
   .Ar sparc ,
   .Ar sparc64 ,
   .Ar sun3 ,
   .Ar vax ,
   or
   .Ar zaurus .
 .El  .El
 .Pp  .Pp
   Examples:
   .D1 \&.Dt FOO 1
   .D1 \&.Dt FOO 4 KM
   .D1 \&.Dt FOO 9 i386
   .Pp
   See also
   .Sx \&Dd
   and
   .Sx \&Os .
   .Ss \&Dv
   Defined variables such as preprocessor constants.
   .Pp
   Examples:
   .D1 \&.Dv BUFSIZ
   .D1 \&.Dv STDOUT_FILENO
   .Pp
   See also
   .Sx \&Er .
   .Ss \&Dx
   Format the DragonFly BSD version provided as an argument, or a default
   value if no argument is provided.
   .Pp
   Examples:
   .D1 \&.Dx 2.4.1
   .D1 \&.Dx
   .Pp
   See also
   .Sx \&At ,
   .Sx \&Bsx ,
   .Sx \&Bx ,
   .Sx \&Fx ,
   .Sx \&Nx ,
   .Sx \&Ox ,
   and
   .Sx \&Ux .
   .Ss \&Ec
   Close a scope started by
   .Sx \&Eo .
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Ec Op Cm TERM
   .Pp
 The  The
 .Sq \&.Ot ,  .Cm TERM
 .Sq \&.Fr ,  argument is used as the enclosure tail, for example, specifying \e(rq
 .Sq \&.Es  will emulate
   .Sx \&Dc .
   .Ss \&Ed
   End a display context started by
   .Sx \&Bd .
   .Ss \&Ef
   Ends a font mode context started by
   .Sx \&Bf .
   .Ss \&Ek
   Ends a keep context started by
   .Sx \&Bk .
   .Ss \&El
   Ends a list context started by
   .Sx \&Bl .
   .Pp
   See also
   .Sx \&Bl
 and  and
 .Sq \&.En ,  .Sx \&It .
 macros are obsolete.  .Ss \&Em
 .\" SECTION  Denotes text that should be emphasised.
   Note that this is a presentation term and should not be used for
   stylistically decorating technical terms.
   .Pp
   Examples:
   .D1 \&.Em Warnings!
   .D1 \&.Em Remarks :
   .Pp
   See also
   .Sx \&Bf ,
   .Sx \&Sy ,
   and
   .Sx \&Li .
   .Ss \&En
   This macro is obsolete and not implemented.
   .Ss \&Eo
   An arbitrary enclosure.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Eo Op Cm TERM
   .Pp
   The
   .Cm TERM
   argument is used as the enclosure head, for example, specifying \e(lq
   will emulate
   .Sx \&Do .
   .Ss \&Er
   Display error constants.
   .Pp
   Examples:
   .D1 \&.Er EPERM
   .D1 \&.Er ENOENT
   .Pp
   See also
   .Sx \&Dv .
   .Ss \&Es
   This macro is obsolete and not implemented.
   .Ss \&Ev
   Environmental variables such as those specified in
   .Xr environ 7 .
   .Pp
   Examples:
   .D1 \&.Ev DISPLAY
   .D1 \&.Ev PATH
   .Ss \&Ex
   Inserts text regarding a utility's exit value.
   This macro must consist of the
   .Fl std
   argument followed by an optional
   .Ar utility .
   If
   .Ar utility
   is not provided, the document's name as stipulated in
   .Sx \&Nm
   is provided.
   .Pp
   See also
   .Sx \&Rv .
   .Ss \&Fa
   Function argument.
   Its syntax is as follows:
   .Bd -ragged -offset indent
   .Pf \. Sx \&Fa
   .Op Cm argtype
   .Cm argname
   .Ed
   .Pp
   This may be invoked for names with or without the corresponding type.
   It is also used to specify the field name of a structure.
   Most often, the
   .Sx \&Fa
   macro is used in the
   .Em SYNOPSIS
   within
   .Sx \&Fo
   section when documenting multi-line function prototypes.
   If invoked with multiple arguments, the arguments are separated by a
   comma.
   Furthermore, if the following macro is another
   .Sx \&Fa ,
   the last argument will also have a trailing comma.
   .Pp
   Examples:
   .D1 \&.Fa \(dqconst char *p\(dq
   .D1 \&.Fa \(dqint a\(dq \(dqint b\(dq \(dqint c\(dq
   .D1 \&.Fa foo
   .Pp
   See also
   .Sx \&Fo .
   .Ss \&Fc
   Ends a function context started by
   .Sx \&Fo .
   .Ss \&Fd
   Historically used to document include files.
   This usage has been deprecated in favour of
   .Sx \&In .
   Do not use this macro.
   .Pp
   See also
   .Sx MANUAL STRUCTURE
   and
   .Sx \&In .
   .Ss \&Fl
   Command-line flag.
   Used when listing arguments to command-line utilities.
   Prints a fixed-width hyphen
   .Sq \-
   directly followed by each argument.
   If no arguments are provided, a hyphen is printed followed by a space.
   If the argument is a macro, a hyphen is prefixed to the subsequent macro
   output.
   .Pp
   Examples:
   .D1 \&.Fl a b c
   .D1 \&.Fl \&Pf a b
   .D1 \&.Fl
   .D1 \&.Op \&Fl o \&Ns \&Ar file
   .Pp
   See also
   .Sx \&Cm .
   .Ss \&Fn
   A function name.
   Its syntax is as follows:
   .Bd -ragged -offset indent
   .Pf \. Ns Sx \&Fn
   .Op Cm functype
   .Cm funcname
   .Op Oo Cm argtype Oc Cm argname
   .Ed
   .Pp
   Function arguments are surrounded in parenthesis and
   are delimited by commas.
   If no arguments are specified, blank parenthesis are output.
   .Pp
   Examples:
   .D1 \&.Fn "int funcname" "int arg0" "int arg1"
   .D1 \&.Fn funcname "int arg0"
   .D1 \&.Fn funcname arg0
   .Bd -literal -offset indent -compact
   \&.Ft functype
   \&.Fn funcname
   .Ed
   .Pp
   See also
   .Sx MANUAL STRUCTURE
   and
   .Sx \&Ft .
   .Ss \&Fo
   Begin a function block.
   This is a multi-line version of
   .Sx \&Fn .
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Fo Cm funcname
   .Pp
   Invocations usually occur in the following context:
   .Bd -ragged -offset indent
   .Pf \. Sx \&Ft Cm functype
   .br
   .Pf \. Sx \&Fo Cm funcname
   .br
   .Pf \. Sx \&Fa Oo Cm argtype Oc Cm argname
   .br
   \.\.\.
   .br
   .Pf \. Sx \&Fc
   .Ed
   .Pp
   A
   .Sx \&Fo
   scope is closed by
   .Pp
   See also
   .Sx MANUAL STRUCTURE ,
   .Sx \&Fa ,
   .Sx \&Fc ,
   and
   .Sx \&Ft .
   .Ss \&Ft
   A function type.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Ft Cm functype
   .Pp
   Examples:
   .D1 \&.Ft int
   .Bd -literal -offset indent -compact
   \&.Ft functype
   \&.Fn funcname
   .Ed
   .Pp
   See also
   .Sx MANUAL STRUCTURE ,
   .Sx \&Fn ,
   and
   .Sx \&Fo .
   .Ss \&Fx
   Format the FreeBSD version provided as an argument, or a default value
   if no argument is provided.
   .Pp
   Examples:
   .D1 \&.Fx 7.1
   .D1 \&.Fx
   .Pp
   See also
   .Sx \&At ,
   .Sx \&Bsx ,
   .Sx \&Bx ,
   .Sx \&Dx ,
   .Sx \&Nx ,
   .Sx \&Ox ,
   and
   .Sx \&Ux .
   .Ss \&Hf
   This macro is obsolete and not implemented.
   .Ss \&Ic
   Designate an internal or interactive command.
   This is similar to
   .Sx \&Cm
   but used for instructions rather than values.
   .Pp
   Examples:
   .D1 \&.Ic hash
   .D1 \&.Ic alias
   .Pp
   Note that using
   .Sx \&Bd No Fl literal
   or
   .Sx \&D1
   is preferred for displaying code; the
   .Sx \&Ic
   macro is used when referring to specific instructions.
   .Ss \&In
   An
   .Dq include
   file.
   In the
   .Em SYNOPSIS
   section (only if invoked as the line macro), the first argument is
   preceded by
   .Dq #include ,
   the arguments is enclosed in angled braces.
   .Pp
   Examples:
   .D1 \&.In sys/types
   .Pp
   See also
   .Sx MANUAL STRUCTURE .
   .Ss \&It
   A list item.
   The syntax of this macro depends on the list type.
   .Pp
   Lists
   of type
   .Fl hang ,
   .Fl ohang ,
   .Fl inset ,
   and
   .Fl diag
   have the following syntax:
   .Pp
   .D1 Pf \. Sx \&It Cm args
   .Pp
   Lists of type
   .Fl bullet ,
   .Fl dash ,
   .Fl enum ,
   .Fl hyphen
   and
   .Fl item
   have the following syntax:
   .Pp
   .D1 Pf \. Sx \&It
   .Pp
   with subsequent lines interpreted within the scope of the
   .Sx \&It
   until either a closing
   .Sx \&El
   or another
   .Sx \&It .
   .Pp
   The
   .Fl tag
   list has the following syntax:
   .Pp
   .D1 Pf \. Sx \&It Op Cm args
   .Pp
   Subsequent lines are interpreted as with
   .Fl bullet
   and family.
   The line arguments correspond to the list's left-hand side; body
   arguments correspond to the list's contents.
   .Pp
   The
   .Fl column
   list is the most complicated.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&It Op Cm args
   .Pp
   The
   .Cm args
   are phrases, a mix of macros and text corresponding to a line column,
   delimited by tabs or the special
   .Sq \&Ta
   pseudo-macro.
   Lines subsequent the
   .Sx \&It
   are interpreted within the scope of the last phrase.
   Calling the pseudo-macro
   .Sq \&Ta
   will open a new phrase scope (this must occur on a macro line to be
   interpreted as a macro).
   Note that the tab phrase delimiter may only be used within the
   .Sx \&It
   line itself.
   Subsequent this, only the
   .Sq \&Ta
   pseudo-macro may be used to delimit phrases.
   Furthermore, note that quoted sections propagate over tab-delimited
   phrases on an
   .Sx \&It ,
   for example,
   .Pp
   .D1 .It \(dqcol1 ; <TAB> col2 ;\(dq \&;
   .Pp
   will preserve the semicolon whitespace except for the last.
   .Pp
   See also
   .Sx \&Bl .
   .Ss \&Lb
   Specify a library.
   The syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Lb Cm library
   .Pp
   The
   .Cm library
   parameter may be a system library, such as
   .Cm libz
   or
   .Cm libpam ,
   in which case a small library description is printed next to the linker
   invocation; or a custom library, in which case the library name is
   printed in quotes.
   This is most commonly used in the
   .Em SYNOPSIS
   section as described in
   .Sx MANUAL STRUCTURE .
   .Pp
   Examples:
   .D1 \&.Lb libz
   .D1 \&.Lb mdoc
   .Ss \&Li
   Denotes text that should be in a literal font mode.
   Note that this is a presentation term and should not be used for
   stylistically decorating technical terms.
   .Pp
   See also
   .Sx \&Bf ,
   .Sx \&Sy ,
   and
   .Sx \&Em .
   .Ss \&Lk
   Format a hyperlink.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Lk Cm uri Op Cm name
   .Pp
   Examples:
   .D1 \&.Lk http://bsd.lv "The BSD.lv Project"
   .D1 \&.Lk http://bsd.lv
   .Pp
   See also
   .Sx \&Mt .
   .Ss \&Lp
   Synonym for
   .Sx \&Pp .
   .Ss \&Ms
   Display a mathematical symbol.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Ms Cm symbol
   .Pp
   Examples:
   .D1 \&.Ms sigma
   .D1 \&.Ms aleph
   .Ss \&Mt
   Format a
   .Dq mailto:
   hyperlink.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Mt Cm address
   .Pp
   Examples:
   .D1 \&.Mt discuss@manpages.bsd.lv
   .Ss \&Nd
   A one-line description of the manual's content.
   This may only be invoked in the
   .Em SYNOPSIS
   section subsequent the
   .Sx \&Nm
   macro.
   .Pp
   Examples:
   .D1 \&.Sx \&Nd mdoc language reference
   .D1 \&.Sx \&Nd format and display UNIX manuals
   .Pp
   The
   .Sx \&Nd
   macro technically accepts child macros and terminates with a subsequent
   .Sx \&Sh
   invocation.
   Do not assume this behaviour: some
   .Xr whatis 1
   database generators are not smart enough to parse more than the line
   arguments and will display macros verbatim.
   .Pp
   See also
   .Sx \&Nm .
   .Ss \&Nm
   The name of the manual page, or \(em in particular in section 1, 6,
   and 8 pages \(em of an additional command or feature documented in
   the manual page.
   When first invoked, the
   .Sx \&Nm
   macro expects a single argument, the name of the manual page.
   Usually, the first invocation happens in the
   .Em NAME
   section of the page.
   The specified name will be remembered and used whenever the macro is
   called again without arguments later in the page.
   The
   .Sx \&Nm
   macro uses
   .Sx Block full-implicit
   semantics when invoked as the first macro on an input line in the
   .Em SYNOPSIS
   section; otherwise, it uses ordinary
   .Sx In-line
   semantics.
   .Pp
   Examples:
   .Bd -literal -offset indent
   \&.Sh SYNOPSIS
   \&.Nm cat
   \&.Op Fl benstuv
   \&.Op Ar
   .Ed
   .Pp
   In the
   .Em SYNOPSIS
   of section 2, 3 and 9 manual pages, use the
   .Sx \&Fn
   macro rather than
   .Sx \&Nm
   to mark up the name of the manual page.
   .Ss \&No
   A
   .Dq noop
   macro used to terminate prior macro contexts.
   .Pp
   Examples:
   .D1 \&.Sx \&Fl ab \&No cd \&Fl ef
   .Ss \&Ns
   Suppress a space.
   Following invocation, text is interpreted as free-form text until a
   macro is encountered.
   .Pp
   Examples:
   .D1 \&.Fl o \&Ns \&Ar output
   .Pp
   See also
   .Sx \&No
   and
   .Sx \&Sm .
   .Ss \&Nx
   Format the NetBSD version provided as an argument, or a default value if
   no argument is provided.
   .Pp
   Examples:
   .D1 \&.Nx 5.01
   .D1 \&.Nx
   .Pp
   See also
   .Sx \&At ,
   .Sx \&Bsx ,
   .Sx \&Bx ,
   .Sx \&Dx ,
   .Sx \&Fx ,
   .Sx \&Ox ,
   and
   .Sx \&Ux .
   .Ss \&Oc
   Closes multi-line
   .Sx \&Oo
   context.
   .Ss \&Oo
   Multi-line version of
   .Sx \&Op .
   .Pp
   Examples:
   .Bd -literal -offset indent -compact
   \&.Oo
   \&.Op Fl flag Ns Ar value
   \&.Oc
   .Ed
   .Ss \&Op
   Command-line option.
   Used when listing options to command-line utilities.
   Prints the argument(s) in brackets.
   .Pp
   Examples:
   .D1 \&.Op \&Fl a \&Ar b
   .D1 \&.Op \&Ar a | b
   .Pp
   See also
   .Sx \&Oo .
   .Ss \&Os
   Document operating system version.
   This is the mandatory third macro of
   any
   .Nm
   file.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Os Op Cm system
   .Pp
   The optional
   .Cm system
   parameter specifies the relevant operating system or environment.
   Left unspecified, it defaults to the local operating system version.
   This is the suggested form.
   .Pp
   Examples:
   .D1 \&.Os
   .D1 \&.Os KTH/CSC/TCS
   .D1 \&.Os BSD 4.3
   .Pp
   See also
   .Sx \&Dd
   and
   .Sx \&Dt .
   .Ss \&Ot
   Unknown usage.
   .Pp
   .Em Remarks :
   this macro has been deprecated.
   .Ss \&Ox
   Format the OpenBSD version provided as an argument, or a default value
   if no argument is provided.
   .Pp
   Examples:
   .D1 \&.Ox 4.5
   .D1 \&.Ox
   .Pp
   See also
   .Sx \&At ,
   .Sx \&Bsx ,
   .Sx \&Bx ,
   .Sx \&Dx ,
   .Sx \&Fx ,
   .Sx \&Nx ,
   and
   .Sx \&Ux .
   .Ss \&Pa
   A file-system path.
   .Pp
   Examples:
   .D1 \&.Pa /usr/bin/mandoc
   .D1 \&.Pa /usr/share/man/man7/mdoc.7
   .Pp
   See also
   .Sx \&Lk .
   .Ss \&Pc
   Close parenthesised context opened by
   .Sx \&Po .
   .Ss \&Pf
   Removes the space
   .Pq Dq prefix
   between its arguments.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. \&Pf Cm prefix suffix
   .Pp
   The
   .Cm suffix
   argument may be a macro.
   .Pp
   Examples:
   .D1 \&.Pf \e. \&Sx \&Pf \&Cm prefix suffix
   .Ss \&Po
   Multi-line version of
   .Sx \&Pq .
   .Ss \&Pp
   Break a paragraph.
   This will assert vertical space between prior and subsequent macros
   and/or text.
   .Ss \&Pq
   Parenthesised enclosure.
   .Pp
   See also
   .Sx \&Po .
   .Ss \&Qc
   Close quoted context opened by
   .Sx \&Qo .
   .Ss \&Ql
   Format a single-quoted literal.
   See also
   .Sx \&Qq
   and
   .Sx \&Sq .
   .Ss \&Qo
   Multi-line version of
   .Sx \&Qq .
   .Ss \&Qq
   Encloses its arguments in
   .Dq typewriter
   double-quotes.
   Consider using
   .Sx \&Dq .
   .Pp
   See also
   .Sx \&Dq ,
   .Sx \&Sq ,
   and
   .Sx \&Qo .
   .Ss \&Re
   Closes a
   .Sx \&Rs
   block.
   Does not have any tail arguments.
   .Ss \&Rs
   Begins a bibliographic
   .Pq Dq reference
   block.
   Does not have any head arguments.
   The block macro may only contain
   .Sx \&%A ,
   .Sx \&%B ,
   .Sx \&%C ,
   .Sx \&%D ,
   .Sx \&%I ,
   .Sx \&%J ,
   .Sx \&%N ,
   .Sx \&%O ,
   .Sx \&%P ,
   .Sx \&%Q ,
   .Sx \&%R ,
   .Sx \&%T ,
   .Sx \&%U ,
   and
   .Sx \&%V
   child macros (at least one must be specified).
   .Pp
   Examples:
   .Bd -literal -offset indent -compact
   \&.Rs
   \&.%A J. E. Hopcroft
   \&.%A J. D. Ullman
   \&.%B Introduction to Automata Theory, Languages, and Computation
   \&.%I Addison-Wesley
   \&.%C Reading, Massachusettes
   \&.%D 1979
   \&.Re
   .Ed
   .Pp
   If an
   .Sx \&Rs
   block is used within a SEE ALSO section, a vertical space is asserted
   before the rendered output, else the block continues on the current
   line.
   .Ss \&Rv
   Inserts text regarding a function call's return value.
   This macro must consist of the
   .Fl std
   argument followed by an optional
   .Ar function .
   If
   .Ar function
   is not provided, the document's name as stipulated by the first
   .Sx \&Nm
   is provided.
   .Pp
   See also
   .Sx \&Ex .
   .Ss \&Sc
   Close single-quoted context opened by
   .Sx \&So .
   .Ss \&Sh
   Begin a new section.
   For a list of conventional manual sections, see
   .Sx MANUAL STRUCTURE .
   These sections should be used unless it's absolutely necessary that
   custom sections be used.
   .Pp
   Section names should be unique so that they may be keyed by
   .Sx \&Sx .
   .Pp
   See also
   .Sx \&Pp ,
   .Sx \&Ss ,
   and
   .Sx \&Sx .
   .Ss \&Sm
   Switches the spacing mode for output generated from macros.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Sm Cm on | off
   .Pp
   By default, spacing is
   .Cm on .
   When switched
   .Cm off ,
   no white space is inserted between macro arguments and between the
   output generated from adjacent macros, but free-form text lines
   still get normal spacing between words and sentences.
   .Ss \&So
   Multi-line version of
   .Sx \&Sq .
   .Ss \&Sq
   Encloses its arguments in
   .Dq typewriter
   single-quotes.
   .Pp
   See also
   .Sx \&Dq ,
   .Sx \&Qq ,
   and
   .Sx \&So .
   .Ss \&Ss
   Begin a new sub-section.
   Unlike with
   .Sx \&Sh ,
   there's no convention for sub-sections.
   Conventional sections, as described in
   .Sx MANUAL STRUCTURE ,
   rarely have sub-sections.
   .Pp
   Sub-section names should be unique so that they may be keyed by
   .Sx \&Sx .
   .Pp
   See also
   .Sx \&Pp ,
   .Sx \&Sh ,
   and
   .Sx \&Sx .
   .Ss \&St
   Replace an abbreviation for a standard with the full form.
   The following standards are recognised:
   .Pp
   .Bl -tag -width "-p1003.1g-2000X" -compact
   .It \-p1003.1-88
   .St -p1003.1-88
   .It \-p1003.1-90
   .St -p1003.1-90
   .It \-p1003.1-96
   .St -p1003.1-96
   .It \-p1003.1-2001
   .St -p1003.1-2001
   .It \-p1003.1-2004
   .St -p1003.1-2004
   .It \-p1003.1-2008
   .St -p1003.1-2008
   .It \-p1003.1
   .St -p1003.1
   .It \-p1003.1b
   .St -p1003.1b
   .It \-p1003.1b-93
   .St -p1003.1b-93
   .It \-p1003.1c-95
   .St -p1003.1c-95
   .It \-p1003.1g-2000
   .St -p1003.1g-2000
   .It \-p1003.1i-95
   .St -p1003.1i-95
   .It \-p1003.2-92
   .St -p1003.2-92
   .It \-p1003.2a-92
   .St -p1003.2a-92
   .It \-p1387.2-95
   .St -p1387.2-95
   .It \-p1003.2
   .St -p1003.2
   .It \-p1387.2
   .St -p1387.2
   .It \-isoC
   .St -isoC
   .It \-isoC-90
   .St -isoC-90
   .It \-isoC-amd1
   .St -isoC-amd1
   .It \-isoC-tcor1
   .St -isoC-tcor1
   .It \-isoC-tcor2
   .St -isoC-tcor2
   .It \-isoC-99
   .St -isoC-99
   .It \-iso9945-1-90
   .St -iso9945-1-90
   .It \-iso9945-1-96
   .St -iso9945-1-96
   .It \-iso9945-2-93
   .St -iso9945-2-93
   .It \-ansiC
   .St -ansiC
   .It \-ansiC-89
   .St -ansiC-89
   .It \-ansiC-99
   .St -ansiC-99
   .It \-ieee754
   .St -ieee754
   .It \-iso8802-3
   .St -iso8802-3
   .It \-ieee1275-94
   .St -ieee1275-94
   .It \-xpg3
   .St -xpg3
   .It \-xpg4
   .St -xpg4
   .It \-xpg4.2
   .St -xpg4.2
   .St -xpg4.3
   .It \-xbd5
   .St -xbd5
   .It \-xcu5
   .St -xcu5
   .It \-xsh5
   .St -xsh5
   .It \-xns5
   .St -xns5
   .It \-xns5.2
   .St -xns5.2
   .It \-xns5.2d2.0
   .St -xns5.2d2.0
   .It \-xcurses4.2
   .St -xcurses4.2
   .It \-susv2
   .St -susv2
   .It \-susv3
   .St -susv3
   .It \-svid4
   .St -svid4
   .El
   .Ss \&Sx
   Reference a section or sub-section.
   The referenced section or sub-section name must be identical to the
   enclosed argument, including whitespace.
   .Pp
   Examples:
   .D1 \&.Sx MANUAL STRUCTURE
   .Ss \&Sy
   Format enclosed arguments in symbolic
   .Pq Dq boldface .
   Note that this is a presentation term and should not be used for
   stylistically decorating technical terms.
   .Pp
   See also
   .Sx \&Bf ,
   .Sx \&Li ,
   and
   .Sx \&Em .
   .Ss \&Tn
   Format a tradename.
   .Pp
   Examples:
   .D1 \&.Tn IBM
   .Ss \&Ud
   Prints out
   .Dq currently under development.
   .Ss \&Ux
   Format the UNIX name.
   Accepts no argument.
   .Pp
   Examples:
   .D1 \&.Ux
   .Pp
   See also
   .Sx \&At ,
   .Sx \&Bsx ,
   .Sx \&Bx ,
   .Sx \&Dx ,
   .Sx \&Fx ,
   .Sx \&Nx ,
   and
   .Sx \&Ox .
   .Ss \&Va
   A variable name.
   .Pp
   Examples:
   .D1 \&.Va foo
   .D1 \&.Va const char *bar ;
   .Ss \&Vt
   A variable type.
   This is also used for indicating global variables in the
   .Em SYNOPSIS
   section, in which case a variable name is also specified.
   Note that it accepts
   .Sx Block partial-implicit
   syntax when invoked as the first macro in the
   .Em SYNOPSIS
   section, else it accepts ordinary
   .Sx In-line
   syntax.
   .Pp
   Note that this should not be confused with
   .Sx \&Ft ,
   which is used for function return types.
   .Pp
   Examples:
   .D1 \&.Vt unsigned char
   .D1 \&.Vt extern const char * const sys_signame[] \&;
   .Pp
   See also
   .Sx MANUAL STRUCTURE
   and
   .Sx \&Va .
   .Ss \&Xc
   Close a scope opened by
   .Sx \&Xo .
   .Ss \&Xo
   Open an extension scope.
   This macro originally existed to extend the 9-argument limit of troff;
   since this limit has been lifted, the macro has been deprecated.
   .Ss \&Xr
   Link to another manual
   .Pq Qq cross-reference .
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&Xr Cm name section
   .Pp
   The
   .Cm name
   and
   .Cm section
   are the name and section of the linked manual.
   If
   .Cm section
   is followed by non-punctuation, an
   .Sx \&Ns
   is inserted into the token stream.
   This behaviour is for compatibility with
   .Xr groff 1 .
   .Pp
   Examples:
   .D1 \&.Xr mandoc 1
   .D1 \&.Xr mandoc 1 \&;
   .D1 \&.Xr mandoc 1 \&Ns s behaviour
   .Ss \&br
   Emits a line-break.
   This macro should not be used; it is implemented for compatibility with
   historical manuals.
   .Pp
   Consider using
   .Sx \&Pp
   in the event of natural paragraph breaks.
   .Ss \&sp
   Emits vertical space.
   This macro should not be used; it is implemented for compatibility with
   historical manuals.
   Its syntax is as follows:
   .Pp
   .D1 Pf \. Sx \&sp Op Cm height
   .Pp
   The
   .Cm height
   argument must be formatted as described in
   .Sx Scaling Widths .
   If unspecified,
   .Sx \&sp
   asserts a single vertical space.
 .Sh COMPATIBILITY  .Sh COMPATIBILITY
 The mdoc language was traditionally a  This section documents compatibility between mandoc and other other
 .Qq roff  troff implementations, at this time limited to GNU troff
 macro package; most existing manuals were written with mdoc syntax  .Pq Qq groff .
 dictated by system-dependent roff installations.  This section documents  The term
 compatibility with these systems.  .Qq historic groff
   refers to groff versions before the
   .Pa doc.tmac
   file re-write
   .Pq somewhere between 1.15 and 1.19 .
 .Pp  .Pp
   Heirloom troff, the other significant troff implementation accepting
   \-mdoc, is similar to historic groff.
   .Pp
 .Bl -dash -compact  .Bl -dash -compact
 .\" LIST-ITEM  
 .It  .It
 .Sq \&.Fo  The \es (font size), \em (font colour), and \eM (font filling colour)
 and  font decoration escapes are all discarded in mandoc.
 .Sq \&.St  
 historically weren't always callable.  Both are now correctly callable.  
 .\" LIST-ITEM  
 .It  .It
 .Sq \&.It \-nested  Old groff fails to assert a newline before
 is assumed for all lists: any list may be nested and  .Sx \&Bd Fl ragged compact .
 .Sq \-enum  
 lists will restart the sequence only for the sub-list.  
 .\" LIST-ITEM  
 .It  .It
 .Sq \&.It \-column  groff behaves inconsistently when encountering
 syntax where column widths may be preceded by other arguments (instead  .Pf non- Sx \&Fa
 of proceeded) is not supported.  children of
 .\" LIST-ITEM  .Sx \&Fo
   regarding spacing between arguments.
   In mandoc, this is not the case: each argument is consistently followed
   by a single space and the trailing
   .Sq \&)
   suppresses prior spacing.
 .It  .It
 The  groff behaves inconsistently when encountering
 .Sq \&.At  .Sx \&Ft
 macro only accepts a single parameter.  
 .\" LIST-ITEM  
 .It  
 The system-name macros (  
 .Ns Sq \&.At ,  
 .Sq \&.Bsx ,  
 .Sq \&.Bx ,  
 .Sq \&.Fx ,  
 .Sq \&.Nx ,  
 .Sq \&.Ox ,  
 and  and
 .Sq \&.Ux )  .Sx \&Fn
 are callable.  in the
 .\" LIST-ITEM  .Em SYNOPSIS :
   at times newline(s) are suppressed depending on whether a prior
   .Sx \&Fn
   has been invoked.
   In mandoc, this is not the case.
   See
   .Sx \&Ft
   and
   .Sx \&Fn
   for the normalised behaviour.
 .It  .It
 Some manuals use  Historic groff does not break before an
 .Sq \&.Li  .Sx \&Fn
 incorrectly by following it with a reserved character and expecting the  when not invoked as the line macro in the
 delimiter to render.  This is not supported.  .Em SYNOPSIS
 .\" LIST-ITEM  section.
 .It  .It
 .Sq \&.Cd  Historic groff formats the
 is callable.  .Sx \&In
 .El  badly: trailing arguments are trashed and
 .\" SECTION  .Em SYNOPSIS
 .Sh SEE ALSO  is not specially treated.
 .Xr mandoc 1 ,  
 .Xr mandoc_char 7  
 .\" SECTION  
 .Sh AUTHORS  
 The  
 .Nm  
 utility was written by  
 .An Kristaps Dzonsons Aq kristaps@openbsd.org .  
 .\" SECTION  
 .Sh CAVEATS  
 There are several ambiguous parts of mdoc.  
 .Pp  
 .Bl -dash -compact  
 .\" LIST-ITEM  
 .It  .It
 .Sq \&.Fa  groff does not accept the
 should be  .Sq \&Ta
 .Sq \&.Va  pseudo-macro as a line macro.
 as function arguments are variables.  mandoc does.
 .\" LIST-ITEM  
 .It  .It
 .Sq \&.Ft  The comment syntax
 should be  .Sq \e\."
 .Sq \&.Vt  is no longer accepted.
 as function return types are still types.  Furthermore, the  
 .Sq \&.Ft  
 should be removed and  
 .Sq \&.Fo ,  
 which ostensibly follows it, should follow the same convention as  
 .Sq \&.Va .  
 .\" LIST-ITEM  
 .It  .It
 .Sq \&.Va  In groff, the
 should formalise that only one or two arguments are acceptable: a  .Sx \&Pa
 variable name and optional, preceding type.  macro does not format its arguments when used in the FILES section under
 .\" LIST-ITEM  certain list types.
   mandoc does.
 .It  .It
 .Sq \&.Fd  Historic groff does not print a dash for empty
 is ambiguous.  It's commonly used to indicate an include file in the  .Sx \&Fl
 synopsis section.  arguments.
 .Sq \&.In  mandoc and newer groff implementations do.
 should be used, instead.  
 .\" LIST-ITEM  
 .It  .It
 Only the  groff behaves irregularly when specifying
 .Sq \-literal  .Sq \ef
 argument to  .Sx Text Decoration
 .Sq \&.Bd  within line-macro scopes.
 makes sense.  The remaining ones should be removed.  mandoc follows a consistent system.
 .\" LIST-ITEM  
 .It  .It
 The  In mandoc, negative scaling units are truncated to zero; groff would
 .Sq \&.Xo  move to prior lines.
   Furthermore, the
   .Sq f
   scaling unit, while accepted, is rendered as the default unit.
   .It
   In quoted literals, groff allowed pair-wise double-quotes to produce a
   standalone double-quote in formatted output.
   This idiosyncratic behaviour is not applicable in mandoc.
   .It
   Display offsets
   .Sx \&Bd
   .Fl offset Ar center
 and  and
 .Sq \&.Xc  .Fl offset Ar right
 macros should be deprecated.  are disregarded in mandoc.
 .\" LIST-ITEM  Furthermore, troff specifies a
   .Fl file Ar file
   argument that is not supported in mandoc.
   Lastly, since text is not right-justified in mandoc (or even groff),
   .Fl ragged
   and
   .Fl filled
   are aliases, as are
   .Fl literal
   and
   .Fl unfilled .
 .It  .It
 The  Historic groff has many un-callable macros.
 .Sq \&.Dt  Most of these (excluding some block-level macros) are now callable.
 macro lacks clarity.  It should be absolutely clear which title will  
 render when formatting the manual page.  
 .\" LIST-ITEM  
 .It  .It
 A  The vertical bar
 .Sq \&.Lx  .Sq \(ba
 should be provided for Linux (\(`a la  made historic groff
 .Sq \&.Ox ,  .Qq go orbital
 .Sq \&.Nx  but has been a proper delimiter since then.
 etc.).  
 .\" LIST-ITEM  
 .It  .It
 There's no way to refer to references in  .Sx \&It Fl nested
 .Sq \&.Rs/.Re  is assumed for all lists (it wasn't in historic groff): any list may be
 blocks.  nested and
   .Fl enum
   lists will restart the sequence only for the sub-list.
   .It
   Some manuals use
   .Sx \&Li
   incorrectly by following it with a reserved character and expecting the
   delimiter to render.
   This is not supported in mandoc.
   .It
   In groff, the
   .Sx \&Cd ,
   .Sx \&Er ,
   .Sx \&Ex ,
   and
   .Sx \&Rv
   macros were stipulated only to occur in certain manual sections.
   mandoc does not have these restrictions.
   .It
   Newer groff and mandoc print
   .Qq AT&T UNIX
   prior to unknown arguments of
   .Sx \&At ;
   older groff did nothing.
 .El  .El
   .Sh SEE ALSO
   .Xr mandoc 1 ,
   .Xr mandoc_char 7
   .Sh AUTHORS
   The
   .Nm
   reference was written by
   .An Kristaps Dzonsons Aq kristaps@bsd.lv .
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