Updated: 2021/Apr/14


MANDOC(1)                   General Commands Manual                  MANDOC(1)

NAME
     mandoc - format manual pages

SYNOPSIS
     mandoc [-ac] [-I os=name] [-K encoding] [-mdoc | -man] [-O options]
            [-T output] [-W level] [file ...]

DESCRIPTION
     The mandoc utility formats manual pages for display.

     By default, mandoc reads mdoc(7) or man(7) text from stdin and produces
     -T locale output.

     The options are as follows:

     -a      If the standard output is a terminal device and -c is not
             specified, use more(1) to paginate the output, just like man(1)
             would.

     -c      Copy the formatted manual pages to the standard output without
             using more(1) to paginate them.  This is the default.  It can be
             specified to override -a.

     -I os=name
             Override the default operating system name for the mdoc(7) Os and
             for the man(7) TH macro.

     -K encoding
             Specify the input encoding.  The supported encoding arguments are
             us-ascii, iso-8859-1, and utf-8.  If not specified, autodetection
             uses the first match in the following list:

             1.   If the first three bytes of the input file are the UTF-8
                  byte order mark (BOM, 0xefbbbf), input is interpreted as
                  utf-8.

             2.   If the first or second line of the input file matches the
                  emacs mode line format

                        .\" -*- [...;] coding: encoding; -*-

                  then input is interpreted according to encoding.

             3.   If the first non-ASCII byte in the file introduces a valid
                  UTF-8 sequence, input is interpreted as utf-8.

             4.   Otherwise, input is interpreted as iso-8859-1.

     -mdoc | -man
             With -mdoc, all input files are interpreted as mdoc(7).  With
             -man, all input files are interpreted as man(7).  By default, the
             input language is automatically detected for each file: if the
             first macro is Dd or Dt, the mdoc(7) parser is used; otherwise,
             the man(7) parser is used.  With other arguments, -m is silently
             ignored.

     -O options
             Comma-separated output options.  See the descriptions of the
             individual output formats for supported options.

     -T output
             Select the output format.  Supported values for the output
             argument are ascii, html, the default of locale, man, markdown,
             pdf, ps, tree, and utf8.

             The special -T lint mode only parses the input and produces no
             output.  It implies -W all and redirects parser messages, which
             usually appear on standard error output, to standard output.

     -W level
             Specify the minimum message level to be reported on the standard
             error output and to affect the exit status.  The level can be
             base, style, warning, error, or unsupp.  The base level
             automatically derives the operating system from the contents of
             the Os macro, from the -Ios command line option, or from the
             uname(3) return value.  The levels openbsd and netbsd are
             variants of base that bypass autodetection and request validation
             of base system conventions for a particular operating system.
             The level all is an alias for base.  By default, mandoc is
             silent.  See EXIT STATUS and DIAGNOSTICS for details.

             The special option -W stop tells mandoc 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 level and stop are requested, they can be joined with a
             comma, for example -W error,stop.

     file    Read from the given input file.  If multiple files are specified,
             they are processed in the given order.  If unspecified, mandoc
             reads from standard input.

     The options -fhklw are also supported and are documented in man(1).  In
     -f and -k mode, mandoc also supports the options -CMmOSs described in the
     apropos(1) manual.  The options -fkl are mutually exclusive and override
     each other.

   ASCII Output
     Use -T ascii to force text output in 7-bit ASCII character encoding
     documented in the ascii(7) manual page, ignoring the locale(1) set in the
     environment.

     Font styles are applied by using back-spaced encoding such that an
     underlined character `c' is rendered as `_\[bs]c', where `\[bs]' is the
     back-space character number 8.  Emboldened characters are rendered as
     `c\[bs]c'.  This markup is typically converted to appropriate terminal
     sequences by the pager or ul(1).  To remove the markup, pipe the output
     to col(1) -b instead.

     The special characters documented in mandoc_char(7) are rendered best-
     effort in an ASCII equivalent.  In particular, opening and closing
     `single quotes' are represented as characters number 0x60 and 0x27,
     respectively, which agrees with all ASCII standards from 1965 to the
     latest revision (2012) and which matches the traditional way in which
     roff(7) formatters represent single quotes in ASCII output.  This correct
     ASCII rendering may look strange with modern Unicode-compatible fonts
     because contrary to ASCII, Unicode uses the code point U+0060 for the
     grave accent only, never for an opening quote.

     The following -O arguments are accepted:

     indent=indent
             The left margin for normal text is set to indent blank characters
             instead of the default of five for mdoc(7) and seven for man(7).
             Increasing this is not recommended; it may result in degraded
             formatting, for example overfull lines or ugly line breaks.  When
             output is to a pager on a terminal that is less than 66 columns
             wide, the default is reduced to three columns.

     mdoc    Format man(7) input files in mdoc(7) output style.  Specifically,
             this suppresses the two additional blank lines near the top and
             the bottom of each page, and it implies -O indent=5.  One useful
             application is for checking that -T man output formats in the
             same way as the mdoc(7) source it was generated from.

     tag[=term]
             If the formatted manual page is opened in a pager, go to the
             definition of the term rather than showing the manual page from
             the beginning.  If no term is specified, reuse the first command
             line argument that is not a section number.  If that argument is
             in apropos(1) key=val format, only the val is used rather than
             the argument as a whole.  This is useful for commands like `man
             -akO tag Ic=ulimit' to search for a keyword and jump right to its
             definition in the matching manual pages.

     width=width
             The output width is set to width instead of the default of 78.
             When output is to a pager on a terminal that is less than 79
             columns wide, the default is reduced to one less than the
             terminal width.  In any case, lines that are output in literal
             mode are never wrapped and may exceed the output width.

   HTML Output
     Output produced by -T html conforms to HTML5 using optional self-closing
     tags.  Default styles use only CSS1.  Equations rendered from eqn(7)
     blocks use MathML.

     The file /usr/share/misc/mandoc.css documents style-sheet classes
     available for customising output.  If a style-sheet is not specified with
     -O style, -T html defaults to simple output (via an embedded style-sheet)
     readable in any graphical or text-based web browser.

     Non-ASCII characters are rendered as hexadecimal Unicode character
     references.

     The following -O arguments are accepted:

     fragment
             Omit the <!DOCTYPE> declaration and the <html>, <head>, and
             <body> elements and only emit the subtree below the <body>
             element.  The style argument will be ignored.  This is useful
             when embedding manual content within existing documents.

     includes=fmt
             The string fmt, for example, ../src/%I.html, is used as a
             template for linked header files (usually via the In macro).
             Instances of `%I' are replaced with the include filename.  The
             default is not to present a hyperlink.

     man=fmt[;fmt]
             The string fmt, for example, ../html%S/%N.%S.html, is used as a
             template for linked manuals (usually via the Xr macro).
             Instances of `%N' and `%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.
             If two formats are given and a file %N.%S exists in the current
             directory, the first format is used; otherwise, the second format
             is used.

     style=style.css
             The file style.css is used for an external style-sheet.  This
             must be a valid absolute or relative URI.

     toc     If an input file contains at least two non-standard sections,
             print a table of contents near the beginning of the output.

   Locale Output
     By default, mandoc automatically selects UTF-8 or ASCII output according
     to the current locale(1).  If any of the environment variables LC_ALL,
     LC_CTYPE, or LANG are set and the first one that is set selects the UTF-8
     character encoding, it produces UTF-8 Output; otherwise, it falls back to
     ASCII Output.  This output mode can also be selected explicitly with -T
     locale.

   Man Output
     Use -T man to translate mdoc(7) input into man(7) output format.  This is
     useful for distributing manual sources to legacy systems lacking mdoc(7)
     formatters.

     If the input format of a file is man(7), the input is copied to the
     output, expanding any roff(7) so requests.  The parser is also run, and
     as usual, the -W level controls which DIAGNOSTICS are displayed before
     copying the input to the output.

   Markdown Output
     Use -T markdown to translate mdoc(7) input to the markdown format
     conforming to John Gruber's 2004 specification:
     http://daringfireball.net/projects/markdown/syntax.text. The output also
     almost conforms to the CommonMark: http://commonmark.org/ specification.

     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.

     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 -T html
     directly.

     The man(7), tbl(7), and eqn(7) input languages are not supported by -T
     markdown output mode.

   PDF Output
     PDF-1.1 output may be generated by -T pdf.  See PostScript Output for -O
     arguments and defaults.

   PostScript Output
     PostScript "Adobe-3.0" Level-2 pages may be generated by -T 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.

     Special characters are rendered as in ASCII Output.

     The following -O arguments are accepted:

     paper=name
             The paper size name may be one of a3, a4, a5, legal, or letter.
             You may also manually specify dimensions as NNxNN, width by
             height in millimetres.  If an unknown value is encountered,
             letter is used.

   UTF-8 Output
     Use -T utf8 to force text output in UTF-8 multi-byte character encoding,
     ignoring the locale(1) settings in the environment.  See ASCII Output
     regarding font styles and -O arguments.

     On operating systems lacking locale or wide character support, and on
     those where the internal character representation is not UCS-4, mandoc
     always falls back to ASCII Output.

   Syntax tree output
     Use -T 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.

     The first paragraph shows meta data found in the mdoc(7) prologue, on the
     man(7) TH line, or the fallbacks used.

     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:

     1.   For macro nodes, the macro name; for text and tbl(7) nodes, the
          content.  There is a special format for eqn(7) nodes.
     2.   Node type (text, elem, block, head, body, body-end, tail, tbl, eqn).
     3.   Flags:
          -   An opening parenthesis if the node is an opening delimiter.
          -   An asterisk if the node starts a new input line.
          -   The input line number (starting at one).
          -   A colon.
          -   The input column number (starting at one).
          -   A closing parenthesis if the node is a closing delimiter.
          -   A full stop if the node ends a sentence.
          -   BROKEN if the node is a block broken by another block.
          -   NOSRC if the node is not in the input file, but automatically
              generated from macros.
          -   NOPRT if the node is not supposed to generate output for any
              output format.

     The following -O argument is accepted:

     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.

ENVIRONMENT
     LC_CTYPE  The character encoding locale(1).  When Locale Output is
               selected, it decides whether to use ASCII or UTF-8 output
               format.  It never affects the interpretation of input files.

     MANPAGER  Any non-empty value of the environment variable MANPAGER is
               used instead of the standard pagination program, more(1); see
               man(1) for details.  Only used if -a or -l is specified.

     PAGER     Specifies the pagination program to use when MANPAGER is not
               defined.  If neither PAGER nor MANPAGER is defined, more(1) -s
               is used.  Only used if -a or -l is specified.

EXIT STATUS
     The mandoc utility exits with one of the following values, controlled by
     the message level associated with the -W option:

     0       No base system convention violations, style suggestions,
             warnings, or errors occurred, or those that did were ignored
             because they were lower than the requested level.
     1       At least one base system convention violation or style suggestion
             occurred, but no warning or error, and -W base or -W style was
             specified.
     2       At least one warning occurred, but no error, and -W warning or a
             lower level was requested.
     3       At least one parsing error occurred, but no unsupported feature
             was encountered, and -W error or a lower level was requested.
     4       At least one unsupported feature was encountered, and -W unsupp
             or a lower level was requested.
     5       Invalid command line arguments were specified.  No input files
             have been read.
     6       An operating system error occurred, for example exhaustion of
             memory, file descriptors, or process table entries.  Such errors
             cause mandoc to exit at once, possibly in the middle of parsing
             or formatting a file.

     Note that selecting -T lint output mode implies -W all.

EXAMPLES
     To page manuals to the terminal:

           $ mandoc -l mandoc.1 man.1 apropos.1 makewhatis.8

     To produce HTML manuals with /usr/share/misc/mandoc.css as the style-
     sheet:

           $ mandoc -T html -O style=/usr/share/misc/mandoc.css mdoc.7 >
           mdoc.7.html

     To check over a large set of manuals:

           $ mandoc -T lint `find /usr/src -name \*\.[1-9]`

     To produce a series of PostScript manuals for A4 paper:

           $ mandoc -T ps -O paper=a4 mdoc.7 man.7 > manuals.ps

     Convert a modern mdoc(7) manual to the older man(7) format, for use on
     systems lacking an mdoc(7) parser:

           $ mandoc -T man foo.mdoc > foo.man

DIAGNOSTICS
     Messages displayed by mandoc follow this format:

           mandoc: file:line:column: level: message: macro arguments (os)

     The first three fields identify the file name, line number, and column
     number of the input file where the message was triggered.  The line and
     column numbers start at 1.  Both are omitted for messages referring to an
     input file as a whole.  All level and message strings are explained
     below.  The name of the macro triggering the message and its arguments
     are omitted where meaningless.  The os operating system specifier is
     omitted for messages that are relevant for all operating systems.  Fatal
     messages about invalid command line arguments or operating system errors,
     for example when memory is exhausted, may also omit the file and level
     fields.

     Message levels have the following meanings:

     unsupp   An input file uses unsupported low-level roff(7) features.  The
              output may be incomplete and/or misformatted, so using GNU troff
              instead of mandoc to process the file may be preferable.

     error    Indicates a risk of information loss or severe misformatting, in
              most cases caused by serious syntax errors.

     warning  Indicates a risk that the information shown or its formatting
              may mismatch the author's intent in minor ways.  Additionally,
              syntax errors are classified at least as warnings, even if they
              do not usually cause misformatting.

     style    An input file uses dubious or discouraged style.  This is not a
              complaint about the syntax, and probably neither formatting nor
              portability are in danger.  While great care is taken to avoid
              false positives on the higher message levels, the style level
              tries to reduce the probability that issues go unnoticed, so it
              may occasionally issue bogus suggestions.  Please use your good
              judgement to decide whether any particular style suggestion
              really justifies a change to the input file.

     base     A convention used in the base system of a specific operating
              system is not adhered to.  These are not markup mistakes, and
              neither the quality of formatting nor portability are in danger.
              Messages of the base level are printed with the more intuitive
              style level tag.

     Messages of the base, style, warning, error, and unsupp levels except
     those about non-existent or unreadable input files are hidden unless
     their level, or a lower level, is requested using a -W option or -T lint
     output mode.

     As indicated below, all base and some style checks are only performed if
     a specific operating system name occurs in the arguments of the -W
     command line option, of the Os macro, of the -Ios command line option,
     or, if neither are present, in the return value of the uname(3) function.

   Conventions for base system manuals
     Mdocdate found
     (mdoc, NetBSD) The Dd macro uses CVS Mdocdate keyword substitution, which
     is not supported by the NetBSD base system.  Consider using the
     conventional "Month dd, yyyy" format instead.

     Mdocdate missing
     (mdoc, OpenBSD) The Dd macro does not use CVS Mdocdate keyword
     substitution, but using it is conventionally expected in the OpenBSD base
     system.

     unknown architecture
     (mdoc, OpenBSD, NetBSD) The third argument of the Dt macro does not match
     any of the architectures this operating system is running on.

     operating system explicitly specified
     (mdoc, OpenBSD, NetBSD) The Os macro has an argument.  In the base
     system, it is conventionally left blank.

     RCS id missing
     (OpenBSD, NetBSD) The manual page lacks the comment line with the RCS
     identifier generated by CVS OpenBSD or NetBSD keyword substitution as
     conventionally used in these operating systems.

     referenced manual not found
     (mdoc) An Xr macro references a manual page that is not found in the base
     system.  The path to look for base system manuals is configurable at
     compile time and defaults to /usr/share/man: /usr/X11R6/man.

   Style suggestions
     legacy man(7) date format
     (mdoc) The Dd macro uses the legacy man(7) date format "yyyy-dd-mm".
     Consider using the conventional mdoc(7) date format "Month dd, yyyy"
     instead.

     normalizing date format to: ...
     (mdoc, man) The Dd or TH macro provides an abbreviated month name or a
     day number with a leading zero.  In the formatted output, the month name
     is written out in full and the leading zero is omitted.

     lower case character in document title
     (mdoc, man) The title is still used as given in the Dt or TH macro.

     duplicate RCS id
     A single manual page contains two copies of the RCS identifier for the
     same operating system.  Consider deleting the later instance and moving
     the first one up to the top of the page.

     possible typo in section name
     (mdoc) Fuzzy string matching revealed that the argument of an Sh macro is
     similar, but not identical to a standard section name.

     unterminated quoted argument
     (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.

     useless macro
     (mdoc) A Bt, Tn, or Ud macro was found.  Simply delete it: it serves no
     useful purpose.

     consider using OS macro
     (mdoc) A string was found in plain text or in a Bx macro that could be
     represented using Ox, Nx, Fx, or Dx.

     errnos out of order
     (mdoc, NetBSD) The Er items in a Bl list are not in alphabetical order.

     duplicate errno
     (mdoc, NetBSD) A Bl list contains two consecutive It entries describing
     the same Er number.

     trailing delimiter
     (mdoc) The last argument of an Ex, Fo, Nd, Nm, Os, Sh, Ss, St, or Sx
     macro ends with a trailing delimiter.  This is usually bad style and
     often indicates typos.  Most likely, the delimiter can be removed.

     no blank before trailing delimiter
     (mdoc) The last argument of a macro that supports trailing delimiter
     arguments is longer than one byte and ends with a trailing delimiter.
     Consider inserting a blank such that the delimiter becomes a separate
     argument, thus moving it out of the scope of the macro.

     fill mode already enabled, skipping
     (man) A fi request occurs even though the document is still in fill mode,
     or already switched back to fill mode.  It has no effect.

     fill mode already disabled, skipping
     (man) An 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.

     verbatim "--", maybe consider using \(em
     (mdoc) Even though the ASCII output device renders an em-dash as "--",
     that is not a good way to write it in an input file because it renders
     poorly on all other output devices.

     function name without markup
     (mdoc) A word followed by an empty pair of parentheses occurs on a text
     line.  Consider using an Fn or Xr macro.

     whitespace at end of input line
     (mdoc, man, roff) Whitespace at the end of input lines is almost never
     semantically significant -- but in the odd case where it might be, it is
     extremely confusing when reviewing and maintaining documents.

     bad comment style
     (roff) Comment lines start with a dot, a backslash, and a double-quote
     character.  The mandoc utility treats the line as a comment line even
     without the backslash, but leaving out the backslash might not be
     portable.

   Warnings related to the document prologue
     missing manual title, using UNTITLED
     (mdoc) A Dt macro has no arguments, or there is no Dt macro before the
     first non-prologue macro.

     missing manual title, using ""
     (man) There is no TH macro, or it has no arguments.

     missing manual section, using ""
     (mdoc, man) A Dt or TH macro lacks the mandatory section argument.

     unknown manual section
     (mdoc) The section number in a Dt line is invalid, but still used.

     missing date, using today's date
     (mdoc, man) The document was parsed as mdoc(7) and it has no Dd macro, or
     the Dd macro has no arguments or only empty arguments; or the document
     was parsed as man(7) and it has no TH macro, or the TH macro has less
     than three arguments or its third argument is empty.

     cannot parse date, using it verbatim
     (mdoc, man) The date given in a Dd or TH macro does not follow the
     conventional format.

     date in the future, using it anyway
     (mdoc, man) The date given in a Dd or TH macro is more than a day ahead
     of the current system time(3).

     missing Os macro, using ""
     (mdoc) The default or current system is not shown in this case.

     late prologue macro
     (mdoc) A Dd or Os macro occurs after some non-prologue macro, but still
     takes effect.

     prologue macros out of order
     (mdoc) The prologue macros are not given in the conventional order Dd,
     Dt, Os.  All three macros are used even when given in another order.

   Warnings regarding document structure
     .so is fragile, better use ln(1)
     (roff) Including files only works when the parser program runs with the
     correct current working directory.

     no document body
     (mdoc, man) The document body contains neither text nor macros.  An empty
     document is shown, consisting only of a header and a footer line.

     content before first section header
     (mdoc, man) Some macros or text precede the first Sh or SH section
     header.  The offending macros and text are parsed and added to the top
     level of the syntax tree, outside any section block.

     first section is not NAME
     (mdoc) The argument of the first Sh macro is not `NAME'.  This may
     confuse makewhatis(8) and apropos(1).

     NAME section without Nm before Nd
     (mdoc) The NAME section does not contain any Nm child macro before the
     first Nd macro.

     NAME section without description
     (mdoc) The NAME section lacks the mandatory Nd child macro.

     description not at the end of NAME
     (mdoc) The NAME section does contain an Nd child macro, but other content
     follows it.

     bad NAME section content
     (mdoc) The NAME section contains plain text or macros other than Nm and
     Nd.

     missing comma before name
     (mdoc) The NAME section contains an Nm macro that is neither the first
     one nor preceded by a comma.

     missing description line, using ""
     (mdoc) The Nd macro lacks the required argument.  The title line of the
     manual will end after the dash.

     description line outside NAME section
     (mdoc) An Nd macro appears outside the NAME section.  The arguments are
     printed anyway and the following text is used for apropos(1), but none of
     that behaviour is portable.

     sections out of conventional order
     (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.

     duplicate section title
     (mdoc) The same standard section title occurs more than once.

     unexpected section
     (mdoc) A standard section header occurs in a section of the manual where
     it normally isn't useful.

     cross reference to self
     (mdoc) An Xr macro refers to a name and section matching the section of
     the present manual page and a name mentioned in an Nm macro in the NAME
     or SYNOPSIS section, or in an Fn or Fo macro in the SYNOPSIS.  Consider
     using Nm or Fn instead of Xr.

     unusual Xr order
     (mdoc) In the SEE ALSO section, an Xr macro with a lower section number
     follows one with a higher number, or two Xr macros referring to the same
     section are out of alphabetical order.

     unusual Xr punctuation
     (mdoc) In the SEE ALSO section, punctuation between two Xr macros differs
     from a single comma, or there is trailing punctuation after the last Xr
     macro.

     AUTHORS section without An macro
     (mdoc) An AUTHORS sections contains no An macros, or only empty ones.
     Probably, there are author names lacking markup.

   Warnings related to macros and nesting
     obsolete macro
     (mdoc) See the mdoc(7) manual for replacements.

     macro neither callable nor escaped
     (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 `\&'.

     skipping paragraph macro
     In mdoc(7) documents, this happens
     -   at the beginning and end of sections and subsections
     -   right before non-compact lists and displays
     -   at the end of items in non-column, non-compact lists
     -   and for multiple consecutive paragraph macros.
     In man(7) documents, it happens
     -   for empty P, PP, and LP macros
     -   for IP macros having neither head nor body arguments
     -   for br or sp right after SH or SS

     moving paragraph macro out of list
     (mdoc) A list item in a Bl list contains a trailing paragraph macro.  The
     paragraph macro is moved after the end of the list.

     skipping no-space macro
     (mdoc) An input line begins with an Ns macro, or the next argument after
     an Ns macro is an isolated closing delimiter.  The macro is ignored.

     blocks badly nested
     (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 "Ao Bo Ac Bc" and
     "Ao Bq Ac".  In these examples, Ac breaks Bo and Bq, respectively.

     nested displays are not portable
     (mdoc) A Bd, D1, or Dl display occurs nested inside another Bd display.
     This works with mandoc, but fails with most other implementations.

     moving content out of list
     (mdoc) A Bl list block contains text or macros before the first It macro.
     The offending children are moved before the beginning of the list.

     first macro on line
     Inside a Bl -column list, a Ta macro occurs as the first macro on a line,
     which is not portable.

     line scope broken
     (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.

   Warnings related to missing arguments
     skipping empty request
     (roff, eqn) The macro name is missing from a macro definition request, or
     an eqn(7) control statement or operation keyword lacks its required
     argument.

     conditional request controls empty scope
     (roff) A conditional request is only useful if any of the following
     follows it on the same logical input line:
     -   The `\{' keyword to open a multi-line scope.
     -   A request or macro or some text, resulting in a single-line scope.
     -   The immediate end of the logical line without any intervening
         whitespace, resulting in next-line scope.
     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 `\' 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 el clause.

     skipping empty macro
     (mdoc) The indicated macro has no arguments and hence no effect.

     empty block
     (mdoc, man) A Bd, Bk, Bl, D1, Dl, MT, RS, or UR block contains nothing in
     its body and will produce no output.

     empty argument, using 0n
     (mdoc) The required width is missing after Bd or Bl -offset or -width.

     missing display type, using -ragged
     (mdoc) The Bd macro is invoked without the required display type.

     list type is not the first argument
     (mdoc) In a Bl macro, at least one other argument precedes the type
     argument.  The mandoc utility copes with any argument order, but some
     other mdoc(7) implementations do not.

     missing -width in -tag list, using 8n
     (mdoc) Every Bl macro having the -tag argument requires -width, too.

     missing utility name, using ""
     (mdoc) The Ex -std macro is called without an argument before Nm has
     first been called with an argument.

     missing function name, using ""
     (mdoc) The Fo macro is called without an argument.  No function name is
     printed.

     empty head in list item
     (mdoc) In a Bl -diag, -hang, -inset, -ohang, or -tag list, an It macro
     lacks the required argument.  The item head is left empty.

     empty list item
     (mdoc) In a Bl -bullet, -dash, -enum, or -hyphen list, an It block is
     empty.  An empty list item is shown.

     missing argument, using next line
     (mdoc) An It macro in a Bd -column list has no arguments.  While mandoc
     uses the text or macros of the following line, if any, for the cell,
     other formatters may misformat the list.

     missing font type, using \fR
     (mdoc) A Bf macro has no argument.  It switches to the default font.

     unknown font type, using \fR
     (mdoc) The Bf argument is invalid.  The default font is used instead.

     nothing follows prefix
     (mdoc) A 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.

     empty reference block
     (mdoc) An Rs macro is immediately followed by an Re macro on the next
     input line.  Such an empty block does not produce any output.

     missing section argument
     (mdoc) An Xr macro lacks its second, section number argument.  The first
     argument, i.e. the name, is printed, but without subsequent parentheses.

     missing -std argument, adding it
     (mdoc) An Ex or Rv macro lacks the required -std argument.  The mandoc
     utility assumes -std even when it is not specified, but other
     implementations may not.

     missing option string, using ""
     (man) The OP macro is invoked without any argument.  An empty pair of
     square brackets is shown.

     missing resource identifier, using ""
     (man) The MT or UR macro is invoked without any argument.  An empty pair
     of angle brackets is shown.

     missing eqn box, using ""
     (eqn) A diacritic mark or a binary operator is found, but there is
     nothing to the left of it.  An empty box is inserted.

   Warnings related to bad macro arguments
     duplicate argument
     (mdoc) A Bd or Bl macro has more than one -compact, more than one
     -offset, or more than one -width argument.  All but the last instances of
     these arguments are ignored.

     skipping duplicate argument
     (mdoc) An An macro has more than one -split or -nosplit argument.  All
     but the first of these arguments are ignored.

     skipping duplicate display type
     (mdoc) A Bd macro has more than one type argument; the first one is used.

     skipping duplicate list type
     (mdoc) A Bl macro has more than one type argument; the first one is used.

     skipping -width argument
     (mdoc) A Bl -column, -diag, -ohang, -inset, or -item list has a -width
     argument.  That has no effect.

     wrong number of cells
     In a line of a Bl -column list, the number of tabs or 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.

     unknown AT&T UNIX version
     (mdoc) An At macro has an invalid argument.  It is used verbatim, with
     "AT&T UNIX " prefixed to it.

     comma in function argument
     (mdoc) An argument of an Fa or Fn macro contains a comma; it should
     probably be split into two arguments.

     parenthesis in function name
     (mdoc) The first argument of an Fc or Fn macro contains an opening or
     closing parenthesis; that's probably wrong, parentheses are added
     automatically.

     unknown library name
     (mdoc, not on OpenBSD) An Lb macro has an unknown name argument and will
     be rendered as "library "name"".

     invalid content in Rs block
     (mdoc) An Rs block contains plain text or non-% macros.  The bogus
     content is left in the syntax tree.  Formatting may be poor.

     invalid Boolean argument
     (mdoc) An Sm macro has an argument other than on or off.  The invalid
     argument is moved out of the macro, which leaves the macro empty, causing
     it to toggle the spacing mode.

     argument contains two font escapes
     (roff) The second argument of a char request contains more than one font
     escape sequence.  A wrong font may remain active after using the
     character.

     unknown font, skipping request
     (man, tbl) A roff(7) ft request or a tbl(7) f layout modifier has an
     unknown font argument.

     odd number of characters in request
     (roff) A tr request contains an odd number of characters.  The last
     character is mapped to the blank character.

   Warnings related to plain text
     blank line in fill mode, using .sp
     (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 sp requests.

     tab in filled text
     (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.

     new sentence, new line
     (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.

     invalid escape sequence
     (roff) An escape sequence has an invalid opening argument delimiter,
     lacks the closing argument delimiter, the argument is of an invalid form,
     or it is a character escape sequence with an invalid name.  If the
     argument is incomplete, \* and \n expand to an empty string, \B to the
     digit `0', and \w to the length of the incomplete argument.  All other
     invalid escape sequences are ignored.

     undefined escape, printing literally
     (roff) In an escape sequence, the first character right after the leading
     backslash is invalid.  That character is printed literally, which is
     equivalent to ignoring the backslash.

     undefined string, using ""
     (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.

   Warnings related to tables
     tbl line starts with span
     (tbl) The first cell in a table layout line is a horizontal span (`s').
     Data provided for this cell is ignored, and nothing is printed in the
     cell.

     tbl column starts with span
     (tbl) The first line of a table layout specification requests a vertical
     span (`^').  Data provided for this cell is ignored, and nothing is
     printed in the cell.

     skipping vertical bar in tbl layout
     (tbl) A table layout specification contains more than two consecutive
     vertical bars.  A double bar is printed, all additional bars are
     discarded.

   Errors related to tables
     non-alphabetic character in tbl options
     (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.

     skipping unknown tbl option
     (tbl) The table options line contains a string of letters that does not
     match any known option name.  The word is ignored.

     missing tbl option argument
     (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.

     wrong tbl option argument size
     (tbl) A table option argument contains an invalid number of characters.
     Both the option and the argument are ignored.

     empty tbl layout
     (tbl) A table layout specification is completely empty, specifying zero
     lines and zero columns.  As a fallback, a single left-justified column is
     used.

     invalid character in tbl layout
     (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.

     unmatched parenthesis in tbl layout
     (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.

     tbl without any data cells
     (tbl) A table does not contain any data cells.  It will probably produce
     no output.

     ignoring data in spanned tbl cell
     (tbl) A table cell is marked as a horizontal span (`s') or vertical span
     (`^') in the table layout, but it contains data.  The data is ignored.

     ignoring extra tbl data cells
     (tbl) A data line contains more cells than the corresponding layout line.
     The data in the extra cells is ignored.

     data block open at end of tbl
     (tbl) A data block is opened with T{, but never closed with a matching
     T}.  The remaining data lines of the table are all put into one cell, and
     any remaining cells stay empty.

   Errors related to roff, mdoc, and man code
     duplicate prologue macro
     (mdoc) One of the prologue macros occurs more than once.  The last
     instance overrides all previous ones.

     skipping late title macro
     (mdoc) The 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 mandoc, traditional semantics is preserved.
     The late macro is discarded including its arguments.

     input stack limit exceeded, infinite loop?
     (roff) Explicit recursion limits are implemented for the following
     features, in order to prevent infinite loops:
     -   expansion of nested escape sequences including expansion of strings
         and number registers,
     -   expansion of nested user-defined macros,
     -   and so file inclusion.
     When a limit is hit, the output is incorrect, typically losing some
     content, but the parser can continue.

     skipping bad character
     (mdoc, man, roff) The input file contains a byte that is not a printable
     ascii(7) character.  The message mentions the character number.  The
     offending byte is replaced with a question mark (`?').  Consider editing
     the input file to replace the byte with an ASCII transliteration of the
     intended character.

     skipping unknown macro
     (mdoc, man, roff) The first identifier on a request or macro line is
     neither recognized as a roff(7) request, nor as a user-defined macro,
     nor, respectively, as an mdoc(7) or man(7) macro.  It may be mistyped or
     unsupported.  The request or macro is discarded including its arguments.

     skipping request outside macro
     (roff) A shift or return request occurs outside any macro definition and
     has no effect.

     skipping insecure request
     (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.

     skipping item outside list
     (mdoc, eqn) An It macro occurs outside any Bl list, or an eqn(7) above
     delimiter occurs outside any pile.  It is discarded including its
     arguments.

     skipping column outside column list
     (mdoc) A Ta macro occurs outside any Bl -column block.  It is discarded
     including its arguments.

     skipping end of block that is not open
     (mdoc, man, eqn, tbl, roff) Various syntax elements can only be used to
     explicitly close blocks that have previously been opened.  An mdoc(7)
     block closing macro, a man(7) ME, RE or UE macro, an eqn(7) right
     delimiter or closing brace, or the end of an equation, table, or roff(7)
     conditional request is encountered but no matching block is open.  The
     offending request or macro is discarded.

     fewer RS blocks open, skipping
     (man) The RE macro is invoked with an argument, but less than the
     specified number of RS blocks is open.  The RE macro is discarded.

     inserting missing end of block
     (mdoc, tbl) Various 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.

     appending missing end of block
     (mdoc, man, eqn, tbl, roff) At the end of the document, an explicit
     mdoc(7) block, a man(7) next-line scope or MT, RS or UR block, an
     equation, table, or roff(7) conditional or ignore block is still open.
     The open block is closed implicitly.

     escaped character not allowed in a name
     (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 am, as, de, ds, nr, or rr request, or any argument of an
     rm request, or the name of a request or user defined macro being called,
     is terminated by an escape sequence.  In the cases of as, ds, and nr, the
     request has no effect at all.  In the cases of am, de, rr, and 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.

     using macro argument outside macro
     (roff) The escape sequence \$ occurs outside any macro definition and
     expands to the empty string.

     argument number is not numeric
     (roff) The argument of the escape sequence \$ is not a digit; the escape
     sequence expands to the empty string.

     NOT IMPLEMENTED: Bd -file
     (mdoc) For security reasons, the Bd macro does not support the -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.

     skipping display without arguments
     (mdoc) A 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.

     missing list type, using -item
     (mdoc) A Bl macro fails to specify the list type.

     argument is not numeric, using 1
     (roff) The argument of a ce request is not a number.

     argument is not a character
     (roff) The first argument of a char request is neither a single ASCII
     character nor a single character escape sequence.  The request is ignored
     including all its arguments.

     missing manual name, using ""
     (mdoc) The first call to Nm, or any call in the NAME section, lacks the
     required argument.

     uname(3) system call failed, using UNKNOWN
     (mdoc) The Os macro is called without arguments, and the uname(3) system
     call failed.  As a workaround, mandoc can be compiled with
     -DOSNAME="\"string\"".

     unknown standard specifier
     (mdoc) An St macro has an unknown argument and is discarded.

     skipping request without numeric argument
     (roff, eqn) An it request or an eqn(7) size or gsize statement has a non-
     numeric or negative argument or no argument at all.  The invalid request
     or statement is ignored.

     excessive shift
     (roff) The argument of a shift request is larger than the number of
     arguments of the macro that is currently being executed.  All macro
     arguments are deleted and \n(.$ is set to zero.

     NOT IMPLEMENTED: .so with absolute path or ".."
     (roff) For security reasons, mandoc allows 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.  mandoc only shows the path as it appears behind so.

     .so request failed
     (roff) Servicing a so request requires reading an external file, but the
     file could not be opened.  mandoc only shows the path as it appears
     behind so.

     skipping all arguments
     (mdoc, man, eqn, roff) An mdoc(7) Bt, Ed, Ef, Ek, El, Lp, Pp, Re, Rs, or
     Ud macro, an It macro in a list that don't support item heads, a man(7)
     LP, P, or PP macro, an eqn(7) EQ or EN macro, or a roff(7) br, fi, or nf
     request or `..' block closing request is invoked with at least one
     argument.  All arguments are ignored.

     skipping excess arguments
     (mdoc, man, roff) A macro or request is invoked with too many arguments:
       -   Fo, MT, PD, RS, UR, ft, or sp with more than one argument
       -   An with another argument after -split or -nosplit
       -   RE with more than one argument or with a non-integer argument
       -   OP or a request of the de family with more than two arguments
       -   Dt with more than three arguments
       -   TH with more than five arguments
       -   Bd, Bk, or Bl with invalid arguments
     The excess arguments are ignored.

   Unsupported features
     input too large
     (mdoc, man) Currently, mandoc 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.

     unsupported control character
     (roff) An ASCII control character supported by other roff(7)
     implementations but not by mandoc was found in an input file.  It is
     replaced by a question mark.

     unsupported escape sequence
     (roff) An input file contains an escape sequence supported by GNU troff
     or Heirloom troff but not by mandoc, and it is likely that this will
     cause information loss or considerable misformatting.

     unsupported roff request
     (roff) An input file contains a roff(7) request supported by GNU troff or
     Heirloom troff but not by mandoc, and it is likely that this will cause
     information loss or considerable misformatting.

     eqn delim option in tbl
     (eqn, tbl) The options line of a table defines equation delimiters.  Any
     equation source code contained in the table will be printed unformatted.

     unsupported table layout modifier
     (tbl) A table layout specification contains an `m' modifier.  The
     modifier is discarded.

     ignoring macro in table
     (tbl, mdoc, man) A table contains an invocation of an mdoc(7) or man(7)
     macro or of an undefined macro.  The macro is ignored, and its arguments
     are handled as if they were a text line.

SEE ALSO
     apropos(1), man(1), eqn(7), man(7), mandoc_char(7), mdoc(7), roff(7),
     tbl(7)

HISTORY
     The mandoc utility first appeared in OpenBSD 4.8.  The option -I appeared
     in OpenBSD 5.2, and -aCcfhKklMSsw in OpenBSD 5.7.

AUTHORS
     The mandoc utility was written by Kristaps Dzonsons <kristaps@bsd.lv> and
     is maintained by Ingo Schwarze <schwarze@openbsd.org>.

NetBSD 9.99                    February 23, 2019                   NetBSD 9.99