.\"	$Id: mandoc.1,v 1.159 2015/04/03 08:46:17 schwarze Exp $
.\"
.\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
.\" Copyright (c) 2012, 2014, 2015 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: April 3 2015 $
.Dt MANDOC 1
.Os
.Sh NAME
.Nm mandoc
.Nd format and display UNIX manuals
.Sh SYNOPSIS
.Nm mandoc
.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 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.
.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
.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 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 h
Display only the SYNOPSIS lines.
Implies
.Fl c .
.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
Input format.
See
.Sx Input Formats
for available formats.
Defaults to
.Fl m Ns Cm andoc .
.It Fl O Ar option
Comma-separated output options.
.It Fl T Ar output
Output format.
See
.Sx Output Formats
for available formats.
Defaults to
.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.
The
.Ar level
can be
.Cm warning ,
.Cm error ,
or
.Cm unsupp ;
.Cm all
is an alias for
.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
Read input from zero or more files.
If unspecified, reads from stdin.
If multiple files are specified,
.Nm
will halt with the first failed parse.
.El
.Pp
In
.Fl f
and
.Fl k
mode,
.Nm
also supports the options
.Fl CMmOSsw
described in the
.Xr apropos 1
manual.
.Ss Input Formats
The
.Nm
utility accepts
.Xr mdoc 7
and
.Xr man 7
input with
.Fl m Ns Cm doc
and
.Fl m Ns Cm an ,
respectively.
The
.Xr mdoc 7
format is
.Em strongly
recommended;
.Xr man 7
should only be used for legacy manuals.
.Pp
A third option,
.Fl m Ns Cm andoc ,
which is also the default, determines encoding on-the-fly: if the first
non-comment macro is
.Sq \&Dd
or
.Sq \&Dt ,
the
.Xr mdoc 7
parser is used; otherwise, the
.Xr man 7
parser is used.
.Pp
If multiple
files are specified with
.Fl m Ns Cm andoc ,
each has its file-type determined this way.
If multiple files are
specified and
.Fl m Ns Cm doc
or
.Fl m Ns Cm an
is specified, then this format is used exclusively.
.Ss Output Formats
The
.Nm
utility accepts the following
.Fl T
arguments, which correspond to output modes:
.Bl -tag -width "-T locale"
.It Fl T Cm ascii
Produce 7-bit ASCII output.
See
.Sx ASCII Output .
.It Fl T Cm html
Produce HTML5, CSS1, and MathML output.
See
.Sx HTML Output .
.It Fl T Cm lint
Parse only: produce no output.
Implies
.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 pdf
Produce PDF output.
See
.Sx PDF Output .
.It Fl T Cm ps
Produce PostScript output.
See
.Sx PostScript Output .
.It Fl T Cm tree
Produce an indented parse tree.
.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.
.Ss ASCII Output
Output produced by
.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
underlined character
.Sq c
is rendered as
.Sq _ Ns \e[bs] Ns c ,
where
.Sq \e[bs]
is the back-space character number 8.
Emboldened characters are rendered as
.Sq c Ns \e[bs] Ns c .
.Pp
The special characters documented in
.Xr mandoc_char 7
are rendered best-effort in an ASCII equivalent.
.Pp
Output width is limited to 78 visible columns unless literal input lines
exceed this limit.
.Pp
The following
.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 ,
which will normalise to \(>=58.
.El
.Ss HTML Output
Output produced by
.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
.Pa example.style.css
file documents style-sheet classes available for customising output.
If a style-sheet is not specified with
.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
Special characters are rendered in decimal-encoded UTF\-8.
.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 ,
for example,
.Ar ../src/%I.html ,
is used as a template for linked header files (usually via the
.Sq \&In
macro).
Instances of
.Sq \&%I
are replaced with the include filename.
The default is not to present a
hyperlink.
.It Cm man Ns = Ns Ar fmt
The string
.Ar fmt ,
for example,
.Ar ../html%S/%N.%S.html ,
is used as a template for linked manuals (usually via the
.Sq \&Xr
macro).
Instances of
.Sq \&%N
and
.Sq %S
are replaced with the linked manual's name and section, respectively.
If no section is included, section 1 is assumed.
The default is not to
present a hyperlink.
.It Cm style Ns = Ns Ar style.css
The file
.Ar style.css
is used for an external style-sheet.
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 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
.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.
Line-height is 1.4m.
.Pp
Special characters are rendered as in
.Sx ASCII Output .
.Pp
The following
.Fl O
arguments are accepted:
.Bl -tag -width Ds
.It Cm paper Ns = Ns Ar name
The paper size
.Ar name
may be one of
.Ar a3 ,
.Ar a4 ,
.Ar a5 ,
.Ar legal ,
or
.Ar letter .
You may also manually specify dimensions as
.Ar NNxNN ,
width by height in millimetres.
If an unknown value is encountered,
.Ar letter
is used.
.El
.Ss UTF\-8 Output
Use
.Fl T Cm utf8
to force a UTF\-8 locale.
See
.Sx Locale Output
for details and options.
.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
.Bl -tag -width Ds -compact
.It 0
No warnings or errors occurred, or those that did were ignored because
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
To page manuals to the terminal:
.Pp
.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
.Ar style.css
as the style-sheet:
.Pp
.Dl $ mandoc \-T html -O style=style.css mdoc.7 \*(Gt mdoc.7.html
.Pp
To check over a large set of manuals:
.Pp
.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
.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
Messages displayed by
.Nm
follow this format:
.Pp
.D1 Nm Ns : Ar file : Ns Ar line : Ns Ar column : level : message : macro args
.Pp
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
.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 name"
.Pq mdoc
The NAME section does not contain any
.Ic \&Nm
child 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 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
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
documents, this happens
.Bl -dash -compact
.It
at the beginning and end of sections and subsections
.It
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
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
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 ".Vt block has child macro"
.Pq mdoc
The
.Ic \&Vt
macro supports plain text arguments only.
Formatting may be ugly and semantic searching
for the affected content might not work.
.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
The
.Sq \e{
keyword to open a multi-line scope.
.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
.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
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 -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 "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
.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
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
.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
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
.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 "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
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
.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
.Sh AUTHORS
.An -nosplit
The
.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 .
.Sh BUGS
In
.Fl T Cm html ,
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 Cm style Ns = Ns Ar really/long/link .