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Diff for /mandoc/mandoc.1 between version 1.76 and 1.174

version 1.76, 2010/08/18 08:41:40 version 1.174, 2017/02/10 15:45:28
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 .\"     $Id$  .\"     $Id$
 .\"  .\"
 .\" Copyright (c) 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>  .\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
   .\" Copyright (c) 2012, 2014-2017 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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 .Nd format and display UNIX manuals  .Nd format and display UNIX manuals
 .Sh SYNOPSIS  .Sh SYNOPSIS
 .Nm mandoc  .Nm mandoc
 .Op Fl V  .Op Fl acfhkl
 .Op Fl f Ns Ar option  .Op Fl I Cm os Ns = Ns Ar name
   .Op Fl K Ar encoding
 .Op Fl m Ns Ar format  .Op Fl m Ns Ar format
 .Op Fl O Ns Ar option  .Op Fl O Ar option
 .Op Fl T Ns Ar output  .Op Fl T Ar output
 .Op Fl W Ns Ar err  .Op Fl W Ar level
 .Op Ar file...  .Op Ar
 .Sh DESCRIPTION  .Sh DESCRIPTION
 The  The
 .Nm  .Nm
 utility formats  utility formats
 .Ux  .Ux
 manual pages for display.  manual pages for display.
 The arguments are as follows:  .Pp
   By default,
   .Nm
   reads
   .Xr mdoc 7
   or
   .Xr man 7
   text from stdin, implying
   .Fl m Ns Cm andoc ,
   and produces
   .Fl T Cm locale
   output.
   .Pp
   The options are as follows:
 .Bl -tag -width Ds  .Bl -tag -width Ds
 .It Fl f Ns Ar option  .It Fl a
 Comma-separated compiler options.  If the standard output is a terminal device and
 See  .Fl c
 .Sx Compiler Options  is not specified, use
 for details.  .Xr more 1
   to paginate the output, just like
   .Xr man 1
   would.
   .It Fl c
   Copy the formatted manual pages to the standard output without using
   .Xr more 1
   to paginate them.
   This is the default.
   It can be specified to override
   .Fl a .
   .It Fl f
   A synonym for
   .Xr whatis 1 .
   This overrides any earlier
   .Fl k
   and
   .Fl l
   options.
   .It Fl h
   Display only the SYNOPSIS lines.
   Implies
   .Fl c .
   .It Fl I Cm os Ns = Ns Ar name
   Override the default operating system
   .Ar name
   for the
   .Xr mdoc 7
   .Sq \&Os
   and for the
   .Xr man 7
   .Sq \&TH
   macro.
   .It Fl K Ar encoding
   Specify the input encoding.
   The supported
   .Ar encoding
   arguments are
   .Cm us-ascii ,
   .Cm iso-8859-1 ,
   and
   .Cm utf-8 .
   If not specified, autodetection uses the first match:
   .Bl -tag -width iso-8859-1
   .It Cm utf-8
   if the first three bytes of the input file
   are the UTF-8 byte order mark (BOM, 0xefbbbf)
   .It Ar encoding
   if the first or second line of the input file matches the
   .Sy emacs
   mode line format
   .Pp
   .D1 .\e" -*- Oo ...; Oc coding: Ar encoding ; No -*-
   .It Cm utf-8
   if the first non-ASCII byte in the file introduces a valid UTF-8 sequence
   .It Cm iso-8859-1
   otherwise
   .El
   .It Fl k
   A synonym for
   .Xr apropos 1 .
   This overrides any earlier
   .Fl f
   and
   .Fl l
   options.
   .It Fl l
   A synonym for
   .Fl a .
   Also reverts any earlier
   .Fl f
   and
   .Fl k
   options.
 .It Fl m Ns Ar format  .It Fl m Ns Ar format
 Input format.  Input format.
 See  See
Line 49  See
Line 137  See
 for available formats.  for available formats.
 Defaults to  Defaults to
 .Fl m Ns Cm andoc .  .Fl m Ns Cm andoc .
 .It Fl O Ns Ar option  .It Fl O Ar option
 Comma-separated output options.  Comma-separated output options.
 .It Fl T Ns Ar output  .It Fl T Ar output
 Output format.  Output format.
 See  See
 .Sx Output Formats  .Sx Output Formats
 for available formats.  for available formats.
 Defaults to  Defaults to
 .Fl T Ns Cm ascii .  .Fl T Cm locale .
 .It Fl V  .It Fl W Ar level
 Print version and exit.  Specify the minimum message
 .It Fl W Ns Ar err  .Ar level
 Comma-separated warning options.  to be reported on the standard error output and to affect the exit status.
 Use  The
 .Fl W Ns Cm all  .Ar level
 to print warnings,  can be
 .Fl W Ns Cm error  .Cm warning ,
 for warnings to be considered errors and cause utility  .Cm error ,
 termination.  or
 Multiple  .Cm unsupp ;
 .Fl W  .Cm all
 arguments may be comma-separated, such as  is an alias for
 .Fl W Ns Cm error , Ns Cm all .  .Cm warning .
   By default,
   .Nm
   is silent.
   See
   .Sx EXIT STATUS
   and
   .Sx DIAGNOSTICS
   for details.
   .Pp
   The special option
   .Fl W Cm stop
   tells
   .Nm
   to exit after parsing a file that causes warnings or errors of at least
   the requested level.
   No formatted output will be produced from that file.
   If both a
   .Ar level
   and
   .Cm stop
   are requested, they can be joined with a comma, for example
   .Fl W Cm error , Ns Cm stop .
 .It Ar file  .It Ar file
 Read input from zero or more files.  Read input from zero or more files.
 If unspecified, reads from stdin.  If unspecified, reads from stdin.
Line 80  If multiple files are specified,
Line 190  If multiple files are specified,
 will halt with the first failed parse.  will halt with the first failed parse.
 .El  .El
 .Pp  .Pp
 By default,  In
   .Fl f
   and
   .Fl k
   mode,
 .Nm  .Nm
 reads  also supports the options
 .Xr mdoc 7  .Fl CMmOSsw
 or  described in the
 .Xr man 7  .Xr apropos 1
 text from stdin, implying  manual.
 .Fl m Ns Cm andoc ,  
 and produces  
 .Fl T Ns Cm ascii  
 output.  
 .Pp  
 .Ex -std mandoc  
 .Ss Input Formats  .Ss Input Formats
 The  The
 .Nm  .Nm
Line 136  specified and
Line 244  specified and
 or  or
 .Fl m Ns Cm an  .Fl m Ns Cm an
 is specified, then this format is used exclusively.  is specified, then this format is used exclusively.
 .Ss Compiler Options  
 Default  
 .Xr mdoc 7  
 and  
 .Xr man 7  
 compilation behaviour may be overridden with the  
 .Fl f  
 flag.  
 .Bl -tag -width Ds  
 .It Fl f Ns Cm ign-errors  
 When parsing multiple files, don't halt when one errors out.  
 Useful with  
 .Fl T Ns Cm lint  
 over a large set of manuals passed on the command line.  
 .It Fl f Ns Cm ign-escape  
 Ignore invalid escape sequences.  
 This is the default, but the option can be used to override an earlier  
 .Fl f Ns Cm strict .  
 .It Fl f Ns Cm ign-scope  
 When rewinding the scope of a block macro, forces the compiler to ignore  
 scope violations.  
 This can seriously mangle the resulting tree.  
 .Pq mdoc only  
 .It Fl f Ns Cm no-ign-escape  
 Do not ignore invalid escape sequences.  
 .It Fl f Ns Cm no-ign-macro  
 Do not ignore unknown macros at the start of input lines.  
 .It Fl f Ns Cm strict  
 Implies  
 .Fl f Ns Cm no-ign-escape  
 and  
 .Fl f Ns Cm no-ign-macro .  
 .El  
 .Ss Output Formats  .Ss Output Formats
 The  The
 .Nm  .Nm
 utility accepts the following  utility accepts the following
 .Fl T  .Fl T
 arguments, which correspond to output modes:  arguments, which correspond to output modes:
 .Bl -tag -width Ds  .Bl -tag -width "-T locale"
 .It Fl T Ns Cm ascii  .It Fl T Cm ascii
 Produce 7-bit ASCII output, backspace-encoded for bold and underline  Produce 7-bit ASCII output.
 styles.  
 This is the default.  
 See  See
 .Sx ASCII Output .  .Sx ASCII Output .
 .It Fl T Ns Cm html  .It Fl T Cm html
 Produce strict HTML-4.01 output, with a sane default style.  Produce HTML5, CSS1, and MathML output.
 See  See
 .Sx HTML Output .  .Sx HTML Output .
 .It Fl T Ns Cm lint  .It Fl T Cm lint
 Parse only: produce no output.  Parse only: produce no output.
 Implies  Implies
 .Fl W Ns Cm all  .Fl W Cm warning .
 and  .It Fl T Cm locale
 .Fl f Ns Cm strict .  Encode output using the current locale.
 .It Fl T Ns Cm pdf  This is the default.
   See
   .Sx Locale Output .
   .It Fl T Cm man
   Produce
   .Xr man 7
   format output.
   See
   .Sx Man Output .
   .It Fl T Cm pdf
 Produce PDF output.  Produce PDF output.
 See  See
 .Sx PDF Output .  .Sx PDF Output .
 .It Fl T Ns Cm ps  .It Fl T Cm ps
 Produce PostScript output.  Produce PostScript output.
 See  See
 .Sx PostScript Output .  .Sx PostScript Output .
 .It Fl T Ns Cm tree  .It Fl T Cm tree
 Produce an indented parse tree.  Produce an indented parse tree.
 .It Fl T Ns Cm xhtml  
 Produce strict XHTML-1.0 output, with a sane default style.  
 See  See
 .Sx XHTML Output .  .Sx Syntax tree output .
   .It Fl T Cm utf8
   Encode output in the UTF\-8 multi-byte format.
   See
   .Sx UTF\-8 Output .
   .It Fl T Cm xhtml
   This is a synonym for
   .Fl T Cm html .
 .El  .El
 .Pp  .Pp
 If multiple input files are specified, these will be processed by the  If multiple input files are specified, these will be processed by the
 corresponding filter in-order.  corresponding filter in-order.
 .Ss ASCII Output  .Ss ASCII Output
 Output produced by  Output produced by
 .Fl T Ns Cm ascii ,  .Fl T Cm ascii
 which is the default, is rendered in standard 7-bit ASCII documented in  is rendered in standard 7-bit ASCII documented in
 .Xr ascii 7 .  .Xr ascii 7 .
 .Pp  .Pp
 Font styles are applied by using back-spaced encoding such that an  Font styles are applied by using back-spaced encoding such that an
Line 238  The following
Line 325  The following
 .Fl O  .Fl O
 arguments are accepted:  arguments are accepted:
 .Bl -tag -width Ds  .Bl -tag -width Ds
   .It Cm indent Ns = Ns Ar indent
   The left margin for normal text is set to
   .Ar indent
   blank characters instead of the default of five for
   .Xr mdoc 7
   and seven for
   .Xr man 7 .
   Increasing this is not recommended; it may result in degraded formatting,
   for example overfull lines or ugly line breaks.
 .It Cm width Ns = Ns Ar width  .It Cm width Ns = Ns Ar width
 The output width is set to  The output width is set to
 .Ar width ,  .Ar width ,
 which will normalise to \(>=60.  which will normalise to \(>=58.
 .El  .El
 .Ss HTML Output  .Ss HTML Output
 Output produced by  Output produced by
 .Fl T Ns Cm html  .Fl T Cm html
 conforms to HTML-4.01 strict.  conforms to HTML5 using optional self-closing tags.
   Default styles use only CSS1.
   Equations rendered from
   .Xr eqn 7
   blocks use MathML.
 .Pp  .Pp
 Font styles and page structure are applied using CSS2.  
 By default, no font style is applied to any text,  
 although CSS2 is hard-coded to format  
 the basic structure of output.  
 .Pp  
 The  The
 .Pa example.style.css  .Pa mandoc.css
 file documents the range of styles applied to output and, if used, will  file documents style-sheet classes available for customising output.
 cause rendered documents to appear as they do in  If a style-sheet is not specified with
 .Fl T Ns Cm ascii .  .Fl O Cm style ,
   .Fl T Cm html
   defaults to simple output (via an embedded style-sheet)
   readable in any graphical or text-based web
   browser.
 .Pp  .Pp
 Special characters are rendered in decimal-encoded UTF-8.  Special characters are rendered in decimal-encoded UTF\-8.
 .Pp  .Pp
 The following  The following
 .Fl O  .Fl O
 arguments are accepted:  arguments are accepted:
 .Bl -tag -width Ds  .Bl -tag -width Ds
   .It Cm fragment
   Omit the <!DOCTYPE> declaration and the <html>, <head>, and <body>
   elements and only emit the subtree below the <body> element.
   The
   .Cm style
   argument will be ignored.
   This is useful when embedding manual content within existing documents.
 .It Cm includes Ns = Ns Ar fmt  .It Cm includes Ns = Ns Ar fmt
 The string  The string
 .Ar fmt ,  .Ar fmt ,
Line 301  is used for an external style-sheet.
Line 407  is used for an external style-sheet.
 This must be a valid absolute or  This must be a valid absolute or
 relative URI.  relative URI.
 .El  .El
   .Ss Locale Output
   Locale-depending output encoding is triggered with
   .Fl T Cm locale .
   This is the default.
   .Pp
   This option is not available on all systems: systems without locale
   support, or those whose internal representation is not natively UCS-4,
   will fall back to
   .Fl T Cm ascii .
   See
   .Sx ASCII Output
   for font style specification and available command-line arguments.
   .Ss Man Output
   Translate input format into
   .Xr man 7
   output format.
   This is useful for distributing manual sources to legacy systems
   lacking
   .Xr mdoc 7
   formatters.
   .Pp
   If
   .Xr mdoc 7
   is passed as input, it is translated into
   .Xr man 7 .
   If the input format is
   .Xr man 7 ,
   the input is copied to the output, expanding any
   .Xr roff 7
   .Sq so
   requests.
   The parser is also run, and as usual, the
   .Fl W
   level controls which
   .Sx DIAGNOSTICS
   are displayed before copying the input to the output.
   .Ss PDF Output
   PDF-1.1 output may be generated by
   .Fl T Cm pdf .
   See
   .Sx PostScript Output
   for
   .Fl O
   arguments and defaults.
 .Ss PostScript Output  .Ss PostScript Output
 PostScript  PostScript
 .Qq Adobe-3.0  .Qq Adobe-3.0
 Level-2 pages may be generated by  Level-2 pages may be generated by
 .Fl T Ns Cm ps .  .Fl T Cm ps .
 Output pages default to letter sized and are rendered in the Times font  Output pages default to letter sized and are rendered in the Times font
 family, 11-point.  family, 11-point.
 Margins are calculated as 1/9 the page length and width.  Margins are calculated as 1/9 the page length and width.
Line 335  If an unknown value is encountered,
Line 485  If an unknown value is encountered,
 .Ar letter  .Ar letter
 is used.  is used.
 .El  .El
 .Ss PDF Output  .Ss UTF\-8 Output
 PDF-1.1 output may be generated by  Use
 .Fl T Ns Cm pdf .  .Fl T Cm utf8
   to force a UTF\-8 locale.
 See  See
 .Sx PostScript Output  .Sx Locale Output
 for  for details and options.
   .Ss Syntax tree output
   Use
   .Fl T Cm tree
   to show a human readable representation of the syntax tree.
   It is useful for debugging the source code of manual pages.
   The exact format is subject to change, so don't write parsers for it.
   .Pp
   The first paragraph shows meta data found in the
   .Xr mdoc 7
   prologue, on the
   .Xr man 7
   .Ic \&TH
   line, or the fallbacks used.
   .Pp
   In the tree dump, each output line shows one syntax tree node.
   Child nodes are indented with respect to their parent node.
   The columns are:
   .Pp
   .Bl -enum -compact
   .It
   For macro nodes, the macro name; for text and
   .Xr tbl 7
   nodes, the content.
   There is a special format for
   .Xr eqn 7
   nodes.
   .It
   Node type (text, elem, block, head, body, body-end, tail, tbl, eqn).
   .It
   Flags:
   .Bl -dash -compact
   .It
   An opening parenthesis if the node is an opening delimiter.
   .It
   An asterisk if the node starts a new input line.
   .It
   The input line number (starting at one).
   .It
   A colon.
   .It
   The input column number (starting at one).
   .It
   A closing parenthesis if the node is a closing delimiter.
   .It
   A full stop if the node ends a sentence.
   .It
   BROKEN if the node is a block broken by another block.
   .It
   NOSRC if the node is not in the input file,
   but automatically generated from macros.
   .It
   NOPRT if the node is not supposed to generate output
   for any output format.
   .El
   .El
   .Pp
   The following
 .Fl O  .Fl O
 arguments and defaults.  argument is accepted:
 .Ss XHTML Output  .Bl -tag -width Ds
 Output produced by  .It Cm noval
 .Fl T Ns Cm xhtml  Skip validation and show the unvalidated syntax tree.
 conforms to XHTML-1.0 strict.  This can help to find out whether a given behaviour is caused by
   the parser or by the validator.
   Meta data is not available in this case.
   .El
   .Sh ENVIRONMENT
   .Bl -tag -width MANPAGER
   .It Ev MANPAGER
   Any non-empty value of the environment variable
   .Ev MANPAGER
   will be used instead of the standard pagination program,
   .Xr more 1 .
   .It Ev PAGER
   Specifies the pagination program to use when
   .Ev MANPAGER
   is not defined.
   If neither PAGER nor MANPAGER is defined,
   .Xr more 1
   .Fl s
   will be used.
   .El
   .Sh EXIT STATUS
   The
   .Nm
   utility exits with one of the following values, controlled by the message
   .Ar level
   associated with the
   .Fl W
   option:
 .Pp  .Pp
 See  .Bl -tag -width Ds -compact
 .Sx HTML Output  .It 0
 for details; beyond generating XHTML tags instead of HTML tags, these  No warnings or errors occurred, or those that did were ignored because
 output modes are identical.  they were lower than the requested
   .Ar level .
   .It 2
   At least one warning occurred, but no error, and
   .Fl W Cm warning
   was specified.
   .It 3
   At least one parsing error occurred,
   but no unsupported feature was encountered, and
   .Fl W Cm error
   or
   .Fl W Cm warning
   was specified.
   .It 4
   At least one unsupported feature was encountered, and
   .Fl W Cm unsupp ,
   .Fl W Cm error
   or
   .Fl W Cm warning
   was specified.
   .It 5
   Invalid command line arguments were specified.
   No input files have been read.
   .It 6
   An operating system error occurred, for example exhaustion
   of memory, file descriptors, or process table entries.
   Such errors cause
   .Nm
   to exit at once, possibly in the middle of parsing or formatting a file.
   .El
   .Pp
   Note that selecting
   .Fl T Cm lint
   output mode implies
   .Fl W Cm warning .
 .Sh EXAMPLES  .Sh EXAMPLES
 To page manuals to the terminal:  To page manuals to the terminal:
 .Pp  .Pp
 .D1 $ mandoc \-Wall,error \-fstrict mandoc.1 2\*(Gt&1 | less  .Dl $ mandoc \-W all,stop mandoc.1 2\*(Gt&1 | less
 .D1 $ mandoc mandoc.1 mdoc.3 mdoc.7 | less  .Dl $ mandoc mandoc.1 mdoc.3 mdoc.7 | less
 .Pp  .Pp
 To produce HTML manuals with  To produce HTML manuals with
 .Ar style.css  .Pa mandoc.css
 as the style-sheet:  as the style-sheet:
 .Pp  .Pp
 .D1 $ mandoc \-Thtml -Ostyle=style.css mdoc.7 \*(Gt mdoc.7.html  .Dl $ mandoc \-T html -O style=mandoc.css mdoc.7 \*(Gt mdoc.7.html
 .Pp  .Pp
 To check over a large set of manuals:  To check over a large set of manuals:
 .Pp  .Pp
 .Dl $ mandoc \-Tlint \-fign-errors `find /usr/src -name \e*\e.[1-9]`  .Dl $ mandoc \-T lint \(gafind /usr/src -name \e*\e.[1-9]\(ga
 .Pp  .Pp
 To produce a series of PostScript manuals for A4 paper:  To produce a series of PostScript manuals for A4 paper:
 .Pp  .Pp
 .D1 $ mandoc \-Tps \-Opaper=a4 mdoc.7 man.7 \*(Gt manuals.ps  .Dl $ mandoc \-T ps \-O paper=a4 mdoc.7 man.7 \*(Gt manuals.ps
 .Sh COMPATIBILITY  .Pp
 This section summarises  Convert a modern
   .Xr mdoc 7
   manual to the older
   .Xr man 7
   format, for use on systems lacking an
   .Xr mdoc 7
   parser:
   .Pp
   .Dl $ mandoc \-T man foo.mdoc \*(Gt foo.man
   .Sh DIAGNOSTICS
   Messages displayed by
 .Nm  .Nm
 compatibility with GNU troff.  follow this format:
 Each input and output format is separately noted.  .Pp
 .Ss ASCII Compatibility  .D1 Nm Ns : Ar file : Ns Ar line : Ns Ar column : level : message : macro args
 .Bl -bullet -compact  .Pp
 .It  Line and column numbers start at 1.
   Both are omitted for messages referring to an input file as a whole.
   Macro names and arguments are omitted where meaningless.
   Fatal messages about invalid command line arguments
   or operating system errors, for example when memory is exhausted,
   may also omit the
   .Ar file
   and
   .Ar level
   fields.
   .Pp
   Message levels have the following meanings:
   .Bl -tag -width "warning"
   .It Cm unsupp
   An input file uses unsupported low-level
   .Xr roff 7
   features.
   The output may be incomplete and/or misformatted,
   so using GNU troff instead of
   .Nm
   to process the file may be preferable.
   .It Cm error
   An input file contains invalid syntax that cannot be safely interpreted.
   By discarding part of the input or inserting missing tokens,
   the parser is able to continue, and the error does not prevent
   generation of formatted output, but typically, preparing that
   output involves information loss, broken document structure
   or unintended formatting, no matter whether
   .Nm
   or GNU troff is used.
   In many cases, the output of
   .Nm
   and GNU troff is identical, but in some,
   .Nm
   is more resilient than GNU troff with respect to malformed input.
   .Pp
   Non-existent or unreadable input files are also reported on the
   .Cm error
   level.
   In that case, the parser cannot even be started and no output
   is produced from those input files.
   .It Cm warning
   An input file uses obsolete, discouraged or non-portable syntax.
   All the same, the meaning of the input is unambiguous and a correct
   rendering can be produced.
   Documents causing warnings may render poorly when using other
   formatting tools instead of
   .Nm .
   .El
   .Pp
   Messages of the
   .Cm warning ,
   .Cm error ,
   and
   .Cm unsupp
   levels except those about non-existent or unreadable input files
   are hidden unless their level, or a lower level, is requested using a
   .Fl W
   option or
   .Fl T Cm lint
   output mode.
   .Ss Warnings related to the document prologue
   .Bl -ohang
   .It Sy "missing manual title, using UNTITLED"
   .Pq mdoc
   A
   .Ic \&Dt
   macro has no arguments, or there is no
   .Ic \&Dt
   macro before the first non-prologue macro.
   .It Sy "missing manual title, using \(dq\(dq"
   .Pq man
   There is no
   .Ic \&TH
   macro, or it has no arguments.
   .It Sy "lower case character in document title"
   .Pq mdoc , man
   The title is still used as given in the
   .Ic \&Dt
   or
   .Ic \&TH
   macro.
   .It Sy "missing manual section, using \(dq\(dq"
   .Pq mdoc , man
   A
   .Ic \&Dt
   or
   .Ic \&TH
   macro lacks the mandatory section argument.
   .It Sy "unknown manual section"
   .Pq mdoc
   The section number in a
   .Ic \&Dt
   line is invalid, but still used.
   .It Sy "missing date, using today's date"
   .Pq mdoc, man
   The document was parsed as
   .Xr mdoc 7
   and it has no
   .Ic \&Dd
   macro, or the
   .Ic \&Dd
   macro has no arguments or only empty arguments;
   or the document was parsed as
   .Xr man 7
   and it has no
   .Ic \&TH
   macro, or the
   .Ic \&TH
   macro has less than three arguments or its third argument is empty.
   .It Sy "cannot parse date, using it verbatim"
   .Pq mdoc , man
   The date given in a
   .Ic \&Dd
   or
   .Ic \&TH
   macro does not follow the conventional format.
   .It Sy "missing Os macro, using \(dq\(dq"
   .Pq mdoc
   The default or current system is not shown in this case.
   .It Sy "duplicate prologue macro"
   .Pq mdoc
   One of the prologue macros occurs more than once.
   The last instance overrides all previous ones.
   .It Sy "late prologue macro"
   .Pq mdoc
   A
   .Ic \&Dd
   or
   .Ic \&Os
   macro occurs after some non-prologue macro, but still takes effect.
   .It Sy "skipping late title macro"
   .Pq mdoc
 The  The
 .Sq \&Bd \-literal  .Ic \&Dt
   macro appears after the first non-prologue macro.
   Traditional formatters cannot handle this because
   they write the page header before parsing the document body.
   Even though this technical restriction does not apply to
   .Nm ,
   traditional semantics is preserved.
   The late macro is discarded including its arguments.
   .It Sy "prologue macros out of order"
   .Pq mdoc
   The prologue macros are not given in the conventional order
   .Ic \&Dd ,
   .Ic \&Dt ,
   .Ic \&Os .
   All three macros are used even when given in another order.
   .El
   .Ss Warnings regarding document structure
   .Bl -ohang
   .It Sy ".so is fragile, better use ln(1)"
   .Pq roff
   Including files only works when the parser program runs with the correct
   current working directory.
   .It Sy "no document body"
   .Pq mdoc , man
   The document body contains neither text nor macros.
   An empty document is shown, consisting only of a header and a footer line.
   .It Sy "content before first section header"
   .Pq mdoc , man
   Some macros or text precede the first
   .Ic \&Sh
   or
   .Ic \&SH
   section header.
   The offending macros and text are parsed and added to the top level
   of the syntax tree, outside any section block.
   .It Sy "first section is not NAME"
   .Pq mdoc
   The argument of the first
   .Ic \&Sh
   macro is not
   .Sq NAME .
   This may confuse
   .Xr makewhatis 8
 and  and
 .Sq \&Bd \-unfilled  .Xr apropos 1 .
 macros of  .It Sy "NAME section without Nm before Nd"
   .Pq mdoc
   The NAME section does not contain any
   .Ic \&Nm
   child macro before the first
   .Ic \&Nd
   macro.
   .It Sy "NAME section without description"
   .Pq mdoc
   The NAME section lacks the mandatory
   .Ic \&Nd
   child macro.
   .It Sy "description not at the end of NAME"
   .Pq mdoc
   The NAME section does contain an
   .Ic \&Nd
   child macro, but other content follows it.
   .It Sy "bad NAME section content"
   .Pq mdoc
   The NAME section contains plain text or macros other than
   .Ic \&Nm
   and
   .Ic \&Nd .
   .It Sy "missing comma before name"
   .Pq mdoc
   The NAME section contains an
   .Ic \&Nm
   macro that is neither the first one nor preceded by a comma.
   .It Sy "missing description line, using \(dq\(dq"
   .Pq mdoc
   The
   .Ic \&Nd
   macro lacks the required argument.
   The title line of the manual will end after the dash.
   .It Sy "sections out of conventional order"
   .Pq mdoc
   A standard section occurs after another section it usually precedes.
   All section titles are used as given,
   and the order of sections is not changed.
   .It Sy "duplicate section title"
   .Pq mdoc
   The same standard section title occurs more than once.
   .It Sy "unexpected section"
   .Pq mdoc
   A standard section header occurs in a section of the manual
   where it normally isn't useful.
   .It Sy "unusual Xr order"
   .Pq mdoc
   In the SEE ALSO section, an
   .Ic \&Xr
   macro with a lower section number follows one with a higher number,
   or two
   .Ic \&Xr
   macros referring to the same section are out of alphabetical order.
   .It Sy "unusual Xr punctuation"
   .Pq mdoc
   In the SEE ALSO section, punctuation between two
   .Ic \&Xr
   macros differs from a single comma, or there is trailing punctuation
   after the last
   .Ic \&Xr
   macro.
   .It Sy "AUTHORS section without An macro"
   .Pq mdoc
   An AUTHORS sections contains no
   .Ic \&An
   macros, or only empty ones.
   Probably, there are author names lacking markup.
   .El
   .Ss "Warnings related to macros and nesting"
   .Bl -ohang
   .It Sy "obsolete macro"
   .Pq mdoc
   See the
 .Xr mdoc 7  .Xr mdoc 7
 in  manual for replacements.
 .Fl T Ns Cm ascii  .It Sy "macro neither callable nor escaped"
 are synonyms, as are \-filled and \-ragged.  .Pq mdoc
 .It  The name of a macro that is not callable appears on a macro line.
 In GNU troff, the  It is printed verbatim.
 .Sq \&Pa  If the intention is to call it, move it to its own input line;
   otherwise, escape it by prepending
   .Sq \e& .
   .It Sy "skipping paragraph macro"
   In
 .Xr mdoc 7  .Xr mdoc 7
 macro does not underline when scoped under an  documents, this happens
 .Sq \&It  .Bl -dash -compact
 in the FILES section.  
 This behaves correctly in  
 .Nm .  
 .It  .It
 A list or display following the  at the beginning and end of sections and subsections
 .Sq \&Ss  
 .Xr mdoc 7  
 macro in  
 .Fl T Ns Cm ascii  
 does not assert a prior vertical break, just as it doesn't with  
 .Sq \&Sh .  
 .It  .It
 The  right before non-compact lists and displays
 .Sq \&na  .It
   at the end of items in non-column, non-compact lists
   .It
   and for multiple consecutive paragraph macros.
   .El
   In
 .Xr man 7  .Xr man 7
 macro in  documents, it happens
 .Fl T Ns Cm ascii  .Bl -dash -compact
 has no effect.  
 .It  .It
 Words aren't hyphenated.  for empty
   .Ic \&P ,
   .Ic \&PP ,
   and
   .Ic \&LP
   macros
 .It  .It
 Sentences are unilaterally monospaced.  for
   .Ic \&IP
   macros having neither head nor body arguments
   .It
   for
   .Ic \&br
   or
   .Ic \&sp
   right after
   .Ic \&SH
   or
   .Ic \&SS
 .El  .El
 .Ss HTML/XHTML Compatibility  .It Sy "moving paragraph macro out of list"
 .Bl -bullet -compact  .Pq mdoc
   A list item in a
   .Ic \&Bl
   list contains a trailing paragraph macro.
   The paragraph macro is moved after the end of the list.
   .It Sy "skipping no-space macro"
   .Pq mdoc
   An input line begins with an
   .Ic \&Ns
   macro.
   The macro is ignored.
   .It Sy "blocks badly nested"
   .Pq mdoc
   If two blocks intersect, one should completely contain the other.
   Otherwise, rendered output is likely to look strange in any output
   format, and rendering in SGML-based output formats is likely to be
   outright wrong because such languages do not support badly nested
   blocks at all.
   Typical examples of badly nested blocks are
   .Qq Ic \&Ao \&Bo \&Ac \&Bc
   and
   .Qq Ic \&Ao \&Bq \&Ac .
   In these examples,
   .Ic \&Ac
   breaks
   .Ic \&Bo
   and
   .Ic \&Bq ,
   respectively.
   .It Sy "nested displays are not portable"
   .Pq mdoc
   A
   .Ic \&Bd ,
   .Ic \&D1 ,
   or
   .Ic \&Dl
   display occurs nested inside another
   .Ic \&Bd
   display.
   This works with
   .Nm ,
   but fails with most other implementations.
   .It Sy "moving content out of list"
   .Pq mdoc
   A
   .Ic \&Bl
   list block contains text or macros before the first
   .Ic \&It
   macro.
   The offending children are moved before the beginning of the list.
   .It Sy "fill mode already enabled, skipping"
   .Pq man
   A
   .Ic \&fi
   request occurs even though the document is still in fill mode,
   or already switched back to fill mode.
   It has no effect.
   .It Sy "fill mode already disabled, skipping"
   .Pq man
   An
   .Ic \&nf
   request occurs even though the document already switched to no-fill mode
   and did not switch back to fill mode yet.
   It has no effect.
   .It Sy "line scope broken"
   .Pq man
   While parsing the next-line scope of the previous macro,
   another macro is found that prematurely terminates the previous one.
   The previous, interrupted macro is deleted from the parse tree.
   .El
   .Ss "Warnings related to missing arguments"
   .Bl -ohang
   .It Sy "skipping empty request"
   .Pq roff , eqn
   The macro name is missing from a macro definition request,
   or an
   .Xr eqn 7
   control statement or operation keyword lacks its required argument.
   .It Sy "conditional request controls empty scope"
   .Pq roff
   A conditional request is only useful if any of the following
   follows it on the same logical input line:
   .Bl -dash -compact
 .It  .It
 The  The
 .Sq \efP  .Sq \e{
 escape will revert the font to the previous  keyword to open a multi-line scope.
 .Sq \ef  
 escape, not to the last rendered decoration, which is now dictated by  
 CSS instead of hard-coded.  
 It also will not span past the current scope,  
 for the same reason.  
 Note that in  
 .Sx ASCII Output  
 mode, this will work fine.  
 .It  .It
   A request or macro or some text, resulting in a single-line scope.
   .It
   The immediate end of the logical line without any intervening whitespace,
   resulting in next-line scope.
   .El
   Here, a conditional request is followed by trailing whitespace only,
   and there is no other content on its logical input line.
   Note that it doesn't matter whether the logical input line is split
   across multiple physical input lines using
   .Sq \e
   line continuation characters.
   This is one of the rare cases
   where trailing whitespace is syntactically significant.
   The conditional request controls a scope containing whitespace only,
   so it is unlikely to have a significant effect,
   except that it may control a following
   .Ic \&el
   clause.
   .It Sy "skipping empty macro"
   .Pq mdoc
   The indicated macro has no arguments and hence no effect.
   .It Sy "empty block"
   .Pq mdoc , man
   A
   .Ic \&Bd ,
   .Ic \&Bk ,
   .Ic \&Bl ,
   .Ic \&D1 ,
   .Ic \&Dl ,
   .Ic \&RS ,
   or
   .Ic \&UR
   block contains nothing in its body and will produce no output.
   .It Sy "empty argument, using 0n"
   .Pq mdoc
   The required width is missing after
   .Ic \&Bd
   or
   .Ic \&Bl
   .Fl offset
   or
   .Fl width.
   .It Sy "missing display type, using -ragged"
   .Pq mdoc
 The  The
   .Ic \&Bd
   macro is invoked without the required display type.
   .It Sy "list type is not the first argument"
   .Pq mdoc
   In a
   .Ic \&Bl
   macro, at least one other argument precedes the type argument.
   The
   .Nm
   utility copes with any argument order, but some other
 .Xr mdoc 7  .Xr mdoc 7
 .Sq \&Bl \-hang  implementations do not.
   .It Sy "missing -width in -tag list, using 8n"
   .Pq mdoc
   Every
   .Ic \&Bl
   macro having the
   .Fl tag
   argument requires
   .Fl width ,
   too.
   .It Sy "missing utility name, using \(dq\(dq"
   .Pq mdoc
   The
   .Ic \&Ex Fl std
   macro is called without an argument before
   .Ic \&Nm
   has first been called with an argument.
   .It Sy "missing function name, using \(dq\(dq"
   .Pq mdoc
   The
   .Ic \&Fo
   macro is called without an argument.
   No function name is printed.
   .It Sy "empty head in list item"
   .Pq mdoc
   In a
   .Ic \&Bl
   .Fl diag ,
   .Fl hang ,
   .Fl inset ,
   .Fl ohang ,
   or
   .Fl tag
   list, an
   .Ic \&It
   macro lacks the required argument.
   The item head is left empty.
   .It Sy "empty list item"
   .Pq mdoc
   In a
   .Ic \&Bl
   .Fl bullet ,
   .Fl dash ,
   .Fl enum ,
   or
   .Fl hyphen
   list, an
   .Ic \&It
   block is empty.
   An empty list item is shown.
   .It Sy "missing font type, using \efR"
   .Pq mdoc
   A
   .Ic \&Bf
   macro has no argument.
   It switches to the default font.
   .It Sy "unknown font type, using \efR"
   .Pq mdoc
   The
   .Ic \&Bf
   argument is invalid.
   The default font is used instead.
   .It Sy "nothing follows prefix"
   .Pq mdoc
   A
   .Ic \&Pf
   macro has no argument, or only one argument and no macro follows
   on the same input line.
   This defeats its purpose; in particular, spacing is not suppressed
   before the text or macros following on the next input line.
   .It Sy "empty reference block"
   .Pq mdoc
   An
   .Ic \&Rs
   macro is immediately followed by an
   .Ic \&Re
   macro on the next input line.
   Such an empty block does not produce any output.
   .It Sy "missing section argument"
   .Pq mdoc
   An
   .Ic \&Xr
   macro lacks its second, section number argument.
   The first argument, i.e. the name, is printed, but without subsequent
   parentheses.
   .It Sy "missing -std argument, adding it"
   .Pq mdoc
   An
   .Ic \&Ex
   or
   .Ic \&Rv
   macro lacks the required
   .Fl std
   argument.
   The
   .Nm
   utility assumes
   .Fl std
   even when it is not specified, but other implementations may not.
   .It Sy "missing option string, using \(dq\(dq"
   .Pq man
   The
   .Ic \&OP
   macro is invoked without any argument.
   An empty pair of square brackets is shown.
   .It Sy "missing resource identifier, using \(dq\(dq"
   .Pq man
   The
   .Ic \&UR
   macro is invoked without any argument.
   An empty pair of angle brackets is shown.
   .It Sy "missing eqn box, using \(dq\(dq"
   .Pq eqn
   A diacritic mark or a binary operator is found,
   but there is nothing to the left of it.
   An empty box is inserted.
   .El
   .Ss "Warnings related to bad macro arguments"
   .Bl -ohang
   .It Sy "unterminated quoted argument"
   .Pq roff
   Macro arguments can be enclosed in double quote characters
   such that space characters and macro names contained in the quoted
   argument need not be escaped.
   The closing quote of the last argument of a macro can be omitted.
   However, omitting it is not recommended because it makes the code
   harder to read.
   .It Sy "duplicate argument"
   .Pq mdoc
   A
   .Ic \&Bd
   or
   .Ic \&Bl
   macro has more than one
   .Fl compact ,
   more than one
   .Fl offset ,
   or more than one
   .Fl width
   argument.
   All but the last instances of these arguments are ignored.
   .It Sy "skipping duplicate argument"
   .Pq mdoc
   An
   .Ic \&An
   macro has more than one
   .Fl split
   or
   .Fl nosplit
   argument.
   All but the first of these arguments are ignored.
   .It Sy "skipping duplicate display type"
   .Pq mdoc
   A
   .Ic \&Bd
   macro has more than one type argument; the first one is used.
   .It Sy "skipping duplicate list type"
   .Pq mdoc
   A
   .Ic \&Bl
   macro has more than one type argument; the first one is used.
   .It Sy "skipping -width argument"
   .Pq mdoc
   A
   .Ic \&Bl
   .Fl column ,
   .Fl diag ,
   .Fl ohang ,
   .Fl inset ,
   or
   .Fl item
   list has a
   .Fl width
   argument.
   That has no effect.
   .It Sy "wrong number of cells"
   In a line of a
   .Ic \&Bl Fl column
   list, the number of tabs or
   .Ic \&Ta
   macros is less than the number expected from the list header line
   or exceeds the expected number by more than one.
   Missing cells remain empty, and all cells exceeding the number of
   columns are joined into one single cell.
   .It Sy "unknown AT&T UNIX version"
   .Pq mdoc
   An
   .Ic \&At
   macro has an invalid argument.
   It is used verbatim, with
   .Qq "AT&T UNIX "
   prefixed to it.
   .It Sy "comma in function argument"
   .Pq mdoc
   An argument of an
   .Ic \&Fa
   or
   .Ic \&Fn
   macro contains a comma; it should probably be split into two arguments.
   .It Sy "parenthesis in function name"
   .Pq mdoc
   The first argument of an
   .Ic \&Fc
   or
   .Ic \&Fn
   macro contains an opening or closing parenthesis; that's probably wrong,
   parentheses are added automatically.
   .It Sy "invalid content in Rs block"
   .Pq mdoc
   An
   .Ic \&Rs
   block contains plain text or non-% macros.
   The bogus content is left in the syntax tree.
   Formatting may be poor.
   .It Sy "invalid Boolean argument"
   .Pq mdoc
   An
   .Ic \&Sm
   macro has an argument other than
   .Cm on
   or
   .Cm off .
   The invalid argument is moved out of the macro, which leaves the macro
   empty, causing it to toggle the spacing mode.
   .It Sy "unknown font, skipping request"
   .Pq man , tbl
   A
   .Xr roff 7
   .Ic \&ft
   request or a
   .Xr tbl 7
   .Ic \&f
   layout modifier has an unknown
   .Ar font
   argument.
   .It Sy "odd number of characters in request"
   .Pq roff
   A
   .Ic \&tr
   request contains an odd number of characters.
   The last character is mapped to the blank character.
   .El
   .Ss "Warnings related to plain text"
   .Bl -ohang
   .It Sy "blank line in fill mode, using .sp"
   .Pq mdoc
   The meaning of blank input lines is only well-defined in non-fill mode:
   In fill mode, line breaks of text input lines are not supposed to be
   significant.
   However, for compatibility with groff, blank lines in fill mode
   are replaced with
   .Ic \&sp
   requests.
   .It Sy "tab in filled text"
   .Pq mdoc , man
   The meaning of tab characters is only well-defined in non-fill mode:
   In fill mode, whitespace is not supposed to be significant
   on text input lines.
   As an implementation dependent choice, tab characters on text lines
   are passed through to the formatters in any case.
   Given that the text before the tab character will be filled,
   it is hard to predict which tab stop position the tab will advance to.
   .It Sy "whitespace at end of input line"
   .Pq mdoc , man , roff
   Whitespace at the end of input lines is almost never semantically
   significant \(em but in the odd case where it might be, it is
   extremely confusing when reviewing and maintaining documents.
   .It Sy "new sentence, new line"
   .Pq mdoc
   A new sentence starts in the middle of a text line.
   Start it on a new input line to help formatters produce correct spacing.
   .It Sy "bad comment style"
   .Pq roff
   Comment lines start with a dot, a backslash, and a double-quote character.
   The
   .Nm
   utility treats the line as a comment line even without the backslash,
   but leaving out the backslash might not be portable.
   .It Sy "invalid escape sequence"
   .Pq roff
   An escape sequence has an invalid opening argument delimiter, lacks the
   closing argument delimiter, or the argument has too few characters.
   If the argument is incomplete,
   .Ic \e*
 and  and
 .Sq \&Bl \-tag  .Ic \en
 list types render similarly (no break following overreached left-hand  expand to an empty string,
 side) due to the expressive constraints of HTML.  .Ic \eB
   to the digit
   .Sq 0 ,
   and
   .Ic \ew
   to the length of the incomplete argument.
   All other invalid escape sequences are ignored.
   .It Sy "undefined string, using \(dq\(dq"
   .Pq roff
   If a string is used without being defined before,
   its value is implicitly set to the empty string.
   However, defining strings explicitly before use
   keeps the code more readable.
   .El
   .Ss "Warnings related to tables"
   .Bl -ohang
   .It Sy "tbl line starts with span"
   .Pq tbl
   The first cell in a table layout line is a horizontal span
   .Pq Sq Cm s .
   Data provided for this cell is ignored, and nothing is printed in the cell.
   .It Sy "tbl column starts with span"
   .Pq tbl
   The first line of a table layout specification
   requests a vertical span
   .Pq Sq Cm ^ .
   Data provided for this cell is ignored, and nothing is printed in the cell.
   .It Sy "skipping vertical bar in tbl layout"
   .Pq tbl
   A table layout specification contains more than two consecutive vertical bars.
   A double bar is printed, all additional bars are discarded.
   .El
   .Ss "Errors related to tables"
   .Bl -ohang
   .It Sy "non-alphabetic character in tbl options"
   .Pq tbl
   The table options line contains a character other than a letter,
   blank, or comma where the beginning of an option name is expected.
   The character is ignored.
   .It Sy "skipping unknown tbl option"
   .Pq tbl
   The table options line contains a string of letters that does not
   match any known option name.
   The word is ignored.
   .It Sy "missing tbl option argument"
   .Pq tbl
   A table option that requires an argument is not followed by an
   opening parenthesis, or the opening parenthesis is immediately
   followed by a closing parenthesis.
   The option is ignored.
   .It Sy "wrong tbl option argument size"
   .Pq tbl
   A table option argument contains an invalid number of characters.
   Both the option and the argument are ignored.
   .It Sy "empty tbl layout"
   .Pq tbl
   A table layout specification is completely empty,
   specifying zero lines and zero columns.
   As a fallback, a single left-justified column is used.
   .It Sy "invalid character in tbl layout"
   .Pq tbl
   A table layout specification contains a character that can neither
   be interpreted as a layout key character nor as a layout modifier,
   or a modifier precedes the first key.
   The invalid character is discarded.
   .It Sy "unmatched parenthesis in tbl layout"
   .Pq tbl
   A table layout specification contains an opening parenthesis,
   but no matching closing parenthesis.
   The rest of the input line, starting from the parenthesis, has no effect.
   .It Sy "tbl without any data cells"
   .Pq tbl
   A table does not contain any data cells.
   It will probably produce no output.
   .It Sy "ignoring data in spanned tbl cell"
   .Pq tbl
   A table cell is marked as a horizontal span
   .Pq Sq Cm s
   or vertical span
   .Pq Sq Cm ^
   in the table layout, but it contains data.
   The data is ignored.
   .It Sy "ignoring extra tbl data cells"
   .Pq tbl
   A data line contains more cells than the corresponding layout line.
   The data in the extra cells is ignored.
   .It Sy "data block open at end of tbl"
   .Pq tbl
   A data block is opened with
   .Cm T{ ,
   but never closed with a matching
   .Cm T} .
   The remaining data lines of the table are all put into one cell,
   and any remaining cells stay empty.
   .El
   .Ss "Errors related to roff, mdoc, and man code"
   .Bl -ohang
   .It Sy "input stack limit exceeded, infinite loop?"
   .Pq roff
   Explicit recursion limits are implemented for the following features,
   in order to prevent infinite loops:
   .Bl -dash -compact
 .It  .It
   expansion of nested escape sequences
   including expansion of strings and number registers,
   .It
   expansion of nested user-defined macros,
   .It
   and
   .Ic \&so
   file inclusion.
   .El
   When a limit is hit, the output is incorrect, typically losing
   some content, but the parser can continue.
   .It Sy "skipping bad character"
   .Pq mdoc , man , roff
   The input file contains a byte that is not a printable
   .Xr ascii 7
   character.
   The message mentions the character number.
   The offending byte is replaced with a question mark
   .Pq Sq \&? .
   Consider editing the input file to replace the byte with an ASCII
   transliteration of the intended character.
   .It Sy "skipping unknown macro"
   .Pq mdoc , man , roff
   The first identifier on a request or macro line is neither recognized as a
   .Xr roff 7
   request, nor as a user-defined macro, nor, respectively, as an
   .Xr mdoc 7
   or
   .Xr man 7
   macro.
   It may be mistyped or unsupported.
   The request or macro is discarded including its arguments.
   .It Sy "skipping insecure request"
   .Pq roff
   An input file attempted to run a shell command
   or to read or write an external file.
   Such attempts are denied for security reasons.
   .It Sy "skipping item outside list"
   .Pq mdoc , eqn
   An
   .Ic \&It
   macro occurs outside any
   .Ic \&Bl
   list, or an
   .Xr eqn 7
   .Ic above
   delimiter occurs outside any pile.
   It is discarded including its arguments.
   .It Sy "skipping column outside column list"
   .Pq mdoc
   A
   .Ic \&Ta
   macro occurs outside any
   .Ic \&Bl Fl column
   block.
   It is discarded including its arguments.
   .It Sy "skipping end of block that is not open"
   .Pq mdoc , man , eqn , tbl , roff
   Various syntax elements can only be used to explicitly close blocks
   that have previously been opened.
   An
   .Xr mdoc 7
   block closing macro, a
   .Xr man 7
   .Ic \&RE
   or
   .Ic \&UE
   macro, an
   .Xr eqn 7
   right delimiter or closing brace, or the end of an equation, table, or
   .Xr roff 7
   conditional request is encountered but no matching block is open.
   The offending request or macro is discarded.
   .It Sy "fewer RS blocks open, skipping"
   .Pq man
 The  The
   .Ic \&RE
   macro is invoked with an argument, but less than the specified number of
   .Ic \&RS
   blocks is open.
   The
   .Ic \&RE
   macro is discarded.
   .It Sy "inserting missing end of block"
   .Pq mdoc , tbl
   Various
   .Xr mdoc 7
   macros as well as tables require explicit closing by dedicated macros.
   A block that doesn't support bad nesting
   ends before all of its children are properly closed.
   The open child nodes are closed implicitly.
   .It Sy "appending missing end of block"
   .Pq mdoc , man , eqn , tbl , roff
   At the end of the document, an explicit
   .Xr mdoc 7
   block, a
 .Xr man 7  .Xr man 7
 .Sq IP  next-line scope or
   .Ic \&RS
   or
   .Ic \&UR
   block, an equation, table, or
   .Xr roff 7
   conditional or ignore block is still open.
   The open block is closed implicitly.
   .It Sy "escaped character not allowed in a name"
   .Pq roff
   Macro, string and register identifiers consist of printable,
   non-whitespace ASCII characters.
   Escape sequences and characters and strings expressed in terms of them
   cannot form part of a name.
   The first argument of an
   .Ic \&am ,
   .Ic \&as ,
   .Ic \&de ,
   .Ic \&ds ,
   .Ic \&nr ,
   or
   .Ic \&rr
   request, or any argument of an
   .Ic \&rm
   request, or the name of a request or user defined macro being called,
   is terminated by an escape sequence.
   In the cases of
   .Ic \&as ,
   .Ic \&ds ,
 and  and
 .Sq TP  .Ic \&nr ,
 lists render similarly.  the request has no effect at all.
   In the cases of
   .Ic \&am ,
   .Ic \&de ,
   .Ic \&rr ,
   and
   .Ic \&rm ,
   what was parsed up to this point is used as the arguments to the request,
   and the rest of the input line is discarded including the escape sequence.
   When parsing for a request or a user-defined macro name to be called,
   only the escape sequence is discarded.
   The characters preceding it are used as the request or macro name,
   the characters following it are used as the arguments to the request or macro.
   .It Sy "NOT IMPLEMENTED: Bd -file"
   .Pq mdoc
   For security reasons, the
   .Ic \&Bd
   macro does not support the
   .Fl file
   argument.
   By requesting the inclusion of a sensitive file, a malicious document
   might otherwise trick a privileged user into inadvertently displaying
   the file on the screen, revealing the file content to bystanders.
   The argument is ignored including the file name following it.
   .It Sy "skipping display without arguments"
   .Pq mdoc
   A
   .Ic \&Bd
   block macro does not have any arguments.
   The block is discarded, and the block content is displayed in
   whatever mode was active before the block.
   .It Sy "missing list type, using -item"
   .Pq mdoc
   A
   .Ic \&Bl
   macro fails to specify the list type.
   .It Sy "missing manual name, using \(dq\(dq"
   .Pq mdoc
   The first call to
   .Ic \&Nm ,
   or any call in the NAME section, lacks the required argument.
   .It Sy "uname(3) system call failed, using UNKNOWN"
   .Pq mdoc
   The
   .Ic \&Os
   macro is called without arguments, and the
   .Xr uname 3
   system call failed.
   As a workaround,
   .Nm
   can be compiled with
   .Sm off
   .Fl D Cm OSNAME=\(dq\e\(dq Ar string Cm \e\(dq\(dq .
   .Sm on
   .It Sy "unknown standard specifier"
   .Pq mdoc
   An
   .Ic \&St
   macro has an unknown argument and is discarded.
   .It Sy "skipping request without numeric argument"
   .Pq roff , eqn
   An
   .Ic \&it
   request or an
   .Xr eqn 7
   .Ic \&size
   or
   .Ic \&gsize
   statement has a non-numeric or negative argument or no argument at all.
   The invalid request or statement is ignored.
   .It Sy "NOT IMPLEMENTED: .so with absolute path or \(dq..\(dq"
   .Pq roff
   For security reasons,
   .Nm
   allows
   .Ic \&so
   file inclusion requests only with relative paths
   and only without ascending to any parent directory.
   By requesting the inclusion of a sensitive file, a malicious document
   might otherwise trick a privileged user into inadvertently displaying
   the file on the screen, revealing the file content to bystanders.
   .Nm
   only shows the path as it appears behind
   .Ic \&so .
   .It Sy ".so request failed"
   .Pq roff
   Servicing a
   .Ic \&so
   request requires reading an external file, but the file could not be
   opened.
   .Nm
   only shows the path as it appears behind
   .Ic \&so .
   .It Sy "skipping all arguments"
   .Pq mdoc , man , eqn , roff
   An
   .Xr mdoc 7
   .Ic \&Bt ,
   .Ic \&Ed ,
   .Ic \&Ef ,
   .Ic \&Ek ,
   .Ic \&El ,
   .Ic \&Lp ,
   .Ic \&Pp ,
   .Ic \&Re ,
   .Ic \&Rs ,
   or
   .Ic \&Ud
   macro, an
   .Ic \&It
   macro in a list that don't support item heads, a
   .Xr man 7
   .Ic \&LP ,
   .Ic \&P ,
   or
   .Ic \&PP
   macro, an
   .Xr eqn 7
   .Ic \&EQ
   or
   .Ic \&EN
   macro, or a
   .Xr roff 7
   .Ic \&br ,
   .Ic \&fi ,
   or
   .Ic \&nf
   request or
   .Sq \&..
   block closing request is invoked with at least one argument.
   All arguments are ignored.
   .It Sy "skipping excess arguments"
   .Pq mdoc , man , roff
   A macro or request is invoked with too many arguments:
   .Bl -dash -offset 2n -width 2n -compact
   .It
   .Ic \&Fo ,
   .Ic \&PD ,
   .Ic \&RS ,
   .Ic \&UR ,
   .Ic \&ft ,
   or
   .Ic \&sp
   with more than one argument
   .It
   .Ic \&An
   with another argument after
   .Fl split
   or
   .Fl nosplit
   .It
   .Ic \&RE
   with more than one argument or with a non-integer argument
   .It
   .Ic \&OP
   or a request of the
   .Ic \&de
   family with more than two arguments
   .It
   .Ic \&Dt
   with more than three arguments
   .It
   .Ic \&TH
   with more than five arguments
   .It
   .Ic \&Bd ,
   .Ic \&Bk ,
   or
   .Ic \&Bl
   with invalid arguments
 .El  .El
   The excess arguments are ignored.
   .El
   .Ss Unsupported features
   .Bl -ohang
   .It Sy "input too large"
   .Pq mdoc , man
   Currently,
   .Nm
   cannot handle input files larger than its arbitrary size limit
   of 2^31 bytes (2 Gigabytes).
   Since useful manuals are always small, this is not a problem in practice.
   Parsing is aborted as soon as the condition is detected.
   .It Sy "unsupported control character"
   .Pq roff
   An ASCII control character supported by other
   .Xr roff 7
   implementations but not by
   .Nm
   was found in an input file.
   It is replaced by a question mark.
   .It Sy "unsupported roff request"
   .Pq roff
   An input file contains a
   .Xr roff 7
   request supported by GNU troff or Heirloom troff but not by
   .Nm ,
   and it is likely that this will cause information loss
   or considerable misformatting.
   .It Sy "eqn delim option in tbl"
   .Pq eqn , tbl
   The options line of a table defines equation delimiters.
   Any equation source code contained in the table will be printed unformatted.
   .It Sy "unsupported table layout modifier"
   .Pq tbl
   A table layout specification contains an
   .Sq Cm m
   modifier.
   The modifier is discarded.
   .It Sy "ignoring macro in table"
   .Pq tbl , mdoc , man
   A table contains an invocation of an
   .Xr mdoc 7
   or
   .Xr man 7
   macro or of an undefined macro.
   The macro is ignored, and its arguments are handled
   as if they were a text line.
   .El
 .Sh SEE ALSO  .Sh SEE ALSO
   .Xr apropos 1 ,
   .Xr man 1 ,
   .Xr eqn 7 ,
 .Xr man 7 ,  .Xr man 7 ,
 .Xr mandoc_char 7 ,  .Xr mandoc_char 7 ,
 .Xr mdoc 7  .Xr mdoc 7 ,
 .Sh AUTHORS  .Xr roff 7 ,
   .Xr tbl 7
   .Sh HISTORY
 The  The
 .Nm  .Nm
 utility was written by  utility first appeared in
 .An Kristaps Dzonsons Aq kristaps@bsd.lv .  .Ox 4.8 .
 .Sh CAVEATS  The option
 The  .Fl I
 .Fl T Ns Cm html  appeared in
   .Ox 5.2 ,
 and  and
 .Fl T Ns Cm xhtml  .Fl aCcfhKklMSsw
 CSS2 styling used for  in
 .Fl m Ns Cm doc  .Ox 5.7 .
 input lists does not render properly in older browsers, such as Internet  .Sh AUTHORS
 Explorer 6 and earlier.  .An -nosplit
 .Pp  
 In  
 .Fl T Ns Cm html  
 and  
 .Fl T Ns Cm xhtml ,  
 the maximum size of an element attribute is determined by  
 .Dv BUFSIZ ,  
 which is usually 1024 bytes.  
 Be aware of this when setting long link  
 formats such as  
 .Fl O Ns Cm style Ns = Ns Ar really/long/link .  
 .Pp  
 Nesting elements within next-line element scopes of  
 .Fl m Ns Cm an ,  
 such as  
 .Sq br  
 within an empty  
 .Sq B ,  
 will confuse  
 .Fl T Ns Cm html  
 and  
 .Fl T Ns Cm xhtml  
 and cause them to forget the formatting of the prior next-line scope.  
 .Pp  
 The  The
 .Sq i  .Nm
 macro in  utility was written by
 .Fl m Ns Cm an  .An Kristaps Dzonsons Aq Mt kristaps@bsd.lv
 should italicise all subsequent text if a line argument is not provided.  and is maintained by
 This behaviour is not implemented.  .An Ingo Schwarze Aq Mt schwarze@openbsd.org .
 The  
 .Sq \(aq  
 control character is an alias for the standard macro control character  
 and does not emit a line-break as stipulated in GNU troff.  
Legend:
Removed from v.1.76  
changed lines
  Added in v.1.174
CVSweb