Now that markdown output is tested for almost everything, test all

[mandoc.git] / mandoc.1

diff --git a/mandoc.1 b/mandoc.1
index 7cf9ca5c9b2f5cf4bb17c6cbff2b0d68a6278e73..8d87007df63e9bac4a5176532ee73d247fe79e33 100644 (file)
--- a/mandoc.1
+++ b/mandoc.1
@@ -1,6 +1,7 @@
-.\"    $Id: mandoc.1,v 1.88 2011/05/20 15:51:18 kristaps Exp $
+.\"    $Id: mandoc.1,v 1.178 2017/03/08 19:40:59 schwarze Exp $

 .\"
 .\"

-.\" 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
 .\" purpose with or without fee is hereby granted, provided that the above
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above


@@ -14,7 +15,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"

-.Dd $Mdocdate: May 20 2011 $
+.Dd $Mdocdate: March 8 2017 $

 .Dt MANDOC 1
 .Os
 .Sh NAME
 .Dt MANDOC 1
 .Os
 .Sh NAME


@@ -22,20 +23,121 @@
 .Nd format and display UNIX manuals
 .Sh SYNOPSIS
 .Nm mandoc
 .Nd format and display UNIX manuals
 .Sh SYNOPSIS
 .Nm mandoc

-.Op Fl V
+.Op Fl acfhkl
+.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 T Ns Ar output
-.Op Fl W Ns Ar level
-.Op Ar file...
+.Op Fl O Ar option
+.Op Fl T Ar output
+.Op Fl W Ar level
+.Op Ar

 .Sh DESCRIPTION
 The
 .Nm
 utility formats
 .Ux
 manual pages for display.
 .Sh DESCRIPTION
 The
 .Nm
 utility formats
 .Ux
 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 a
+If the standard output is a terminal device and
+.Fl c
+is not specified, use
+.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 in the following
+list:
+.Bl -enum
+.It
+If the first three bytes of the input file are the UTF-8 byte order
+mark (BOM, 0xefbbbf), input is interpreted as
+.Cm utf-8 .
+.It
+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 -*-
+.Pp
+then input is interpreted according to
+.Ar encoding .
+.It
+If the first non-ASCII byte in the file introduces a valid UTF-8
+sequence, input is interpreted as
+.Cm utf-8 .
+.It
+Otherwise, input is interpreted as
+.Cm iso-8859-1 .
+.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
 Input format.
 See
 .It Fl m Ns Ar format
 Input format.
 See


@@ -43,18 +145,16 @@ See
 for available formats.
 Defaults to
 .Fl m Ns Cm andoc .
 for available formats.
 Defaults to
 .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.
 See
 .Sx Output Formats
 for available formats.
 Defaults to
 Output format.
 See
 .Sx Output Formats
 for available formats.
 Defaults to

-.Fl T Ns Cm ascii .
-.It Fl V
-Print version and exit.
-.It Fl W Ns Ar level
+.Fl T Cm locale .
+.It Fl W Ar level

 Specify the minimum message
 .Ar level
 to be reported on the standard error output and to affect the exit status.
 Specify the minimum message
 .Ar level
 to be reported on the standard error output and to affect the exit status.


@@ -64,12 +164,13 @@ can be
 .Cm warning ,
 .Cm error ,
 or
 .Cm warning ,
 .Cm error ,
 or

-.Cm fatal .
-The default is
-.Fl W Ns Cm fatal ;
-.Fl W Ns Cm all
+.Cm unsupp ;
+.Cm all

 is an alias for
 is an alias for

-.Fl W Ns Cm warning .
+.Cm warning .
+By default,
+.Nm
+is silent.

 See
 .Sx EXIT STATUS
 and
 See
 .Sx EXIT STATUS
 and


@@ -77,7 +178,7 @@ and
 for details.
 .Pp
 The special option
 for details.
 .Pp
 The special option

-.Fl W Ns Cm stop
+.Fl W Cm stop

 tells
 .Nm
 to exit after parsing a file that causes warnings or errors of at least
 tells
 .Nm
 to exit after parsing a file that causes warnings or errors of at least


@@ -88,7 +189,7 @@ If both a
 and
 .Cm stop
 are requested, they can be joined with a comma, for example
 and
 .Cm stop
 are requested, they can be joined with a comma, for example

-.Fl W Ns Cm error , Ns Cm stop .
+.Fl W Cm error , Ns Cm stop .

 .It Ar file
 Read input from zero or more files.
 If unspecified, reads from stdin.
 .It Ar file
 Read input from zero or more files.
 If unspecified, reads from stdin.


@@ -97,17 +198,17 @@ If multiple files are specified,
 will halt with the first failed parse.
 .El
 .Pp
 will halt with the first failed parse.
 .El
 .Pp

-By default,
+In
+.Fl f
+and
+.Fl k
+mode,

 .Nm
 .Nm

-reads
-.Xr mdoc 7
-or
-.Xr man 7
-text from stdin, implying
-.Fl m Ns Cm andoc ,
-and produces
-.Fl T Ns Cm ascii
-output.
+also supports the options
+.Fl CMmOSsw
+described in the
+.Xr apropos 1
+manual.

 .Ss Input Formats
 The
 .Nm
 .Ss Input Formats
 The
 .Nm


@@ -157,68 +258,63 @@ The
 utility accepts the following
 .Fl T
 arguments, which correspond to output modes:
 utility accepts the following
 .Fl T
 arguments, which correspond to output modes:

-.Bl -tag -width Ds
-.It Fl T Ns Cm utf8
-Encode output in the UTF-8 multi-byte format.
-See
-.Xr UTF-8 Output .
-.It Fl T Ns Cm locale
-Encode output using the current
-.Xr locale 1 .
-See
-.Sx Locale Output .
-.It Fl T Ns Cm ascii
+.Bl -tag -width "-T markdown"
+.It Fl T Cm ascii

 Produce 7-bit ASCII output.
 Produce 7-bit ASCII output.

-This is the default.

 See
 .Sx ASCII Output .
 See
 .Sx ASCII Output .

-.It Fl T Ns Cm html
-Produce strict CSS1/HTML-4.01 output.
+.It Fl T Cm html
+Produce HTML5, CSS1, and MathML output.

 See
 .Sx HTML Output .
 See
 .Sx HTML Output .

-.It Fl T Ns Cm lint
+.It Fl T Cm lint

 Parse only: produce no output.
 Implies
 Parse only: produce no output.
 Implies

-.Fl W Ns Cm warning .
-.It Fl T Ns Cm pdf
+.Fl W Cm warning .
+.It Fl T Cm locale
+Encode output using the current locale.
+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 markdown
+Produce output in
+.Sy markdown
+format.
+See
+.Sx Markdown Output .
+.It Fl T Cm pdf

 Produce PDF output.
 See
 .Sx PDF Output .
 Produce PDF output.
 See
 .Sx PDF Output .

-.It Fl T Ns Cm ps
+.It Fl T Cm ps

 Produce PostScript output.
 See
 .Sx PostScript Output .
 Produce PostScript output.
 See
 .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 CSS1/XHTML-1.0 output.

 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
 .Pp
 If multiple input files are specified, these will be processed by the
 corresponding filter in-order.
 .El
 .Pp
 If multiple input files are specified, these will be processed by the
 corresponding filter in-order.

-.Ss UTF-8 Output
-Use
-.Fl T Ns Cm utf8
-to force a UTF-8 locale.
-See
-.Sx Locale Output
-for details and options.
-.Ss Locale Output
-Locale-depending output encoding is triggered with
-.Fl T Ns Cm locale .
-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 Ns Cm ascii .
-See
-.Sx ASCII Output
-for font style specification and available command-line arguments.

 .Ss ASCII Output
 Output produced by
 .Ss ASCII Output
 Output produced by

-.Fl T Ns Cm ascii ,
-which is the default, is rendered in standard 7-bit ASCII documented in
+.Fl T Cm ascii
+is rendered in standard 7-bit ASCII documented in

 .Xr ascii 7 .
 .Pp
 Font styles are applied by using back-spaced encoding such that an
 .Xr ascii 7 .
 .Pp
 Font styles are applied by using back-spaced encoding such that an


@@ -235,9 +331,6 @@ Emboldened characters are rendered as
 The special characters documented in
 .Xr mandoc_char 7
 are rendered best-effort in an ASCII equivalent.
 The special characters documented in
 .Xr mandoc_char 7
 are rendered best-effort in an ASCII equivalent.

-If no equivalent is found,
-.Sq \&?
-is used instead.

 .Pp
 Output width is limited to 78 visible columns unless literal input lines
 exceed this limit.
 .Pp
 Output width is limited to 78 visible columns unless literal input lines
 exceed this limit.


@@ -246,31 +339,52 @@ The following
 .Fl O
 arguments are accepted:
 .Bl -tag -width Ds
 .Fl O
 arguments are accepted:
 .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
 The output width is set to
 .Ar width ,
 .It Cm width Ns = Ns Ar width
 The output width is set to
 .Ar width ,

-which will normalise to \(>=60.
+which will normalise to \(>=58.

 .El
 .Ss HTML Output
 Output produced by
 .El
 .Ss HTML Output
 Output produced by

-.Fl T Ns Cm html
-conforms to HTML-4.01 strict.
+.Fl T Cm html
+conforms to HTML5 using optional self-closing tags.
+Default styles use only CSS1.
+Equations rendered from
+.Xr eqn 7
+blocks use MathML.

 .Pp
 The
 .Pp
 The

-.Pa example.style.css
+.Pa mandoc.css

 file documents style-sheet classes available for customising output.
 If a style-sheet is not specified with
 file documents style-sheet classes available for customising output.
 If a style-sheet is not specified with

-.Fl O Ns Ar style ,
-.Fl T Ns Cm html
-defaults to simple output readable in any graphical or text-based web
+.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
 browser.
 .Pp

-Special characters are rendered in decimal-encoded UTF-8.
+Special characters are rendered in decimal-encoded UTF\-8.

 .Pp
 The following
 .Fl O
 arguments are accepted:
 .Bl -tag -width Ds
 .Pp
 The following
 .Fl O
 arguments are accepted:
 .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
 The string
 .Ar fmt ,
 .It Cm includes Ns = Ns Ar fmt
 The string
 .Ar fmt ,


@@ -307,11 +421,89 @@ is used for an external style-sheet.
 This must be a valid absolute or
 relative URI.
 .El
 This must be a valid absolute or
 relative URI.
 .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 Markdown Output
+Translate
+.Xr mdoc 7
+input to the
+.Sy markdown
+format conforming to
+.Lk http://daringfireball.net/projects/markdown/syntax.text\
+ "John Gruber's 2004 specification" .
+The output also almost conforms to the
+.Lk http://commonmark.org/ CommonMark
+specification.
+.Pp
+The character set used for the markdown output is ASCII.
+Non-ASCII characters are encoded as HTML entities.
+Since that is not possible in literal font contexts, because these
+are rendered as code spans and code blocks in the markdown output,
+non-ASCII characters are transliterated to ASCII approximations in
+these contexts.
+.Pp
+Markdown is a very weak markup language, so all semantic markup is
+lost, and even part of the presentational markup may be lost.
+Do not use this as an intermediate step in converting to HTML;
+instead, use
+.Fl T Cm html
+directly.
+.Pp
+The
+.Xr man 7 ,
+.Xr tbl 7 ,
+and
+.Xr eqn 7
+input languages are not supported by
+.Fl T Cm markdown
+output mode.
+.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
 PostScript
 .Qq Adobe-3.0
 Level-2 pages may be generated by
 .Ss PostScript Output
 PostScript
 .Qq Adobe-3.0
 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
 family, 11-point.
 Margins are calculated as 1/9 the page length and width.
 Output pages default to letter sized and are rendered in the Times font
 family, 11-point.
 Margins are calculated as 1/9 the page length and width.


@@ -341,23 +533,95 @@ If an unknown value is encountered,
 .Ar letter
 is used.
 .El
 .Ar letter
 is used.
 .El

-.Ss PDF Output
-PDF-1.1 output may be generated by
-.Fl T Ns Cm pdf .
+.Ss UTF\-8 Output
+Use
+.Fl T Cm utf8
+to force a UTF\-8 locale.

 See
 See

-.Sx PostScript Output
-for
-.Fl O
-arguments and defaults.
-.Ss XHTML Output
-Output produced by
-.Fl T Ns Cm xhtml
-conforms to XHTML-1.0 strict.
+.Sx Locale Output
+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
 .Pp

-See
-.Sx HTML Output
-for details; beyond generating XHTML tags instead of HTML tags, these
-output modes are identical.
+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
+argument is accepted:
+.Bl -tag -width Ds
+.It Cm noval
+Skip validation and show the unvalidated syntax tree.
+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
 .Sh EXIT STATUS
 The
 .Nm


@@ -374,88 +638,114 @@ they were lower than the requested
 .Ar level .
 .It 2
 At least one warning occurred, but no error, and
 .Ar level .
 .It 2
 At least one warning occurred, but no error, and

-.Fl W Ns Cm warning
+.Fl W Cm warning

 was specified.
 .It 3
 was specified.
 .It 3

-At least one parsing error occurred, but no fatal error, and
-.Fl W Ns Cm error
+At least one parsing error occurred,
+but no unsupported feature was encountered, and
+.Fl W Cm error

 or
 or

-.Fl W Ns Cm warning
+.Fl W Cm warning

 was specified.
 .It 4
 was specified.
 .It 4

-A fatal parsing error occurred.
+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
 .It 5
 Invalid command line arguments were specified.
 No input files have been read.
 .It 6

-An operating system error occurred, for example memory exhaustion or an
-error accessing input files.
+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
 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 Ns Cm lint
+.Fl T Cm lint

 output mode implies
 output mode implies

-.Fl W Ns Cm warning .
+.Fl W Cm warning .

 .Sh EXAMPLES
 To page manuals to the terminal:
 .Pp
 .Sh EXAMPLES
 To page manuals to the terminal:
 .Pp

-.Dl $ mandoc \-Wall,stop mandoc.1 2\*(Gt&1 | less
+.Dl $ mandoc \-W all,stop mandoc.1 2\*(Gt&1 | less

 .Dl $ mandoc mandoc.1 mdoc.3 mdoc.7 | less
 .Pp
 To produce HTML manuals with
 .Dl $ mandoc mandoc.1 mdoc.3 mdoc.7 | less
 .Pp
 To produce HTML manuals with

-.Ar style.css
+.Pa mandoc.css

 as the style-sheet:
 .Pp
 as the style-sheet:
 .Pp

-.Dl $ 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
 To check over a large set of manuals:
 .Pp
 .Pp
 To check over a large set of manuals:
 .Pp

-.Dl $ mandoc \-Tlint `find /usr/src -name \e*\e.[1-9]`
+.Dl $ mandoc \-T lint \(gafind /usr/src -name \e*\e.[1-9]\(ga

 .Pp
 To produce a series of PostScript manuals for A4 paper:
 .Pp
 .Pp
 To produce a series of PostScript manuals for A4 paper:
 .Pp

-.Dl $ 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
+.Pp
+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
 .Sh DIAGNOSTICS

-Standard error messages reporting parsing errors are prefixed by
+Messages displayed by
+.Nm
+follow this format:

 .Pp
 .Pp

-.Sm off
-.D1 Ar file : line : column : \ level :
-.Sm on
+.D1 Nm Ns : Ar file : Ns Ar line : Ns Ar column : level : message : macro args

 .Pp
 .Pp

-where the fields have the following meanings:
-.Bl -tag -width "column"
-.It Ar file
-The name of the input file causing the message.
-.It Ar line
-The line number in that input file.
-Line numbering starts at 1.
-.It Ar column
-The column number in that input file.
-Column numbering starts at 1.
-If the issue is caused by a word, the column number usually
-points to the first character of the word.
-.It Ar level
-The message level, printed in capital letters.
-.El
+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"
 .Pp
 Message levels have the following meanings:
 .Bl -tag -width "warning"

-.It Cm fatal
-The parser is unable to parse a given input file at all.
-No formatted output is produced from that input file.
-.It Cm error
-An input file contains syntax that cannot be safely interpreted,
-either because it is invalid or because
+.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
 .Nm

-does not implement it yet.
+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
 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.
+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
 .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


@@ -466,139 +756,1173 @@ formatting tools instead of
 .El
 .Pp
 Messages of the
 .El
 .Pp
 Messages of the

-.Cm warning
+.Cm warning ,
+.Cm error ,

 and
 and

-.Cm error
-levels are hidden unless their level, or a lower level, is requested using a
+.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 W
 option or

-.Fl T Ns Cm lint
+.Fl T Cm lint

 output mode.
 output mode.

-.Pp
-The
-.Nm
-utility may also print messages related to invalid command line arguments
-or operating system errors, for example when memory is exhausted or
-input files cannot be read.
-Such messages do not carry the prefix described above.
-.Sh COMPATIBILITY
-This section summarises
-.Nm
-compatibility with GNU troff.
-Each input and output format is separately noted.
-.Ss ASCII Compatibility
-.Bl -bullet -compact
-.It
-Unrenderable unicode codepoints specified with
-.Sq \e[uNNNN]
-escapes are printed as
-.Sq \&?
-in mandoc.
-In GNU troff, these raise an error.
-.It
+.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
+.Xr apropos 1 .
+.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
 and

-.Sq \&Bd \-unfilled
-macros of
+.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 "description line outside NAME section"
+.Pq mdoc
+An
+.Ic \&Nd
+macro appears outside the NAME section.
+The arguments are printed anyway and the following text is used for
+.Xr apropos 1 ,
+but none of that behaviour is portable.
+.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
-.Fl T Ns Cm ascii
-are synonyms, as are \-filled and \-ragged.
-.It
-In historic GNU troff, the
-.Sq \&Pa
+manual for replacements.
+.It Sy "macro neither callable nor escaped"
+.Pq mdoc
+The name of a macro that is not callable appears on a macro line.
+It is printed verbatim.
+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
-.Sq \&It
-in the FILES section.
-This behaves correctly in
-.Nm .
+documents, this happens
+.Bl -dash -compact

 .It
 .It

-A list or display following the
-.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 .
+at the beginning and end of sections and subsections

 .It
 .It

-The
-.Sq \&na
+right before non-compact lists and displays
+.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
-.Fl T Ns Cm ascii
-has no effect.
+documents, it happens
+.Bl -dash -compact
+.It
+for empty
+.Ic \&P ,
+.Ic \&PP ,
+and
+.Ic \&LP
+macros
+.It
+for
+.Ic \&IP
+macros having neither head nor body arguments

 .It
 .It

-Words aren't hyphenated.
+for
+.Ic \&br
+or
+.Ic \&sp
+right after
+.Ic \&SH
+or
+.Ic \&SS
+.El
+.It Sy "moving paragraph macro out of list"
+.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
 .El

-.Ss HTML/XHTML Compatibility
-.Bl -bullet -compact
+.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
 The
 .It
 The

-.Sq \efP
-escape will revert the font to the previous
-.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.
+.Sq \e{
+keyword to open a multi-line scope.
+.It
+A request or macro or some text, resulting in a single-line scope.

 .It
 .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
+.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
 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
+.Ic \en
+expand to an empty string,
+.Ic \eB
+to the digit
+.Sq 0 ,

 and
 and

-.Sq \&Bl \-tag
-list types render similarly (no break following overreached left-hand
-side) due to the expressive constraints of HTML.
+.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
+expansion of nested escape sequences
+including expansion of strings and number registers,

 .It
 .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
-lists render similarly.
+.Ic \&nr ,
+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
+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
 .El
 .Sh SEE ALSO

+.Xr apropos 1 ,
+.Xr man 1 ,

 .Xr eqn 7 ,
 .Xr man 7 ,
 .Xr mandoc_char 7 ,
 .Xr mdoc 7 ,
 .Xr roff 7 ,
 .Xr tbl 7
 .Xr eqn 7 ,
 .Xr man 7 ,
 .Xr mandoc_char 7 ,
 .Xr mdoc 7 ,
 .Xr roff 7 ,
 .Xr tbl 7

-.Sh AUTHORS
+.Sh HISTORY

 The
 .Nm
 The
 .Nm

-utility was written by
-.An Kristaps Dzonsons Aq kristaps@bsd.lv .
-.Sh CAVEATS
-In
-.Fl T Ns Cm html
+utility first appeared in
+.Ox 4.8 .
+The option
+.Fl I
+appeared in
+.Ox 5.2 ,

 and
 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
+.Fl aCcfhKklMSsw
+in
+.Ox 5.7 .
+.Sh AUTHORS
+.An -nosplit

 The
 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.
+.Nm
+utility was written by
+.An Kristaps Dzonsons Aq Mt kristaps@bsd.lv
+and is maintained by
+.An Ingo Schwarze Aq Mt schwarze@openbsd.org .