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NAME

     mdoc.samples - tutorial sampler for writing BSD manuals with -mdoc

SYNOPSIS

     man mdoc.samples

DESCRIPTION

     A tutorial sampler for writing BSD manual pages with the -mdoc macro
     package, a content-based and domain-based formatting package for
     troff(1).  Its predecessor, the -man(7) package, addressed page layout
     leaving the manipulation of fonts and other typesetting details to the
     individual author.  In -mdoc, page layout macros make up the page
     structure domain which consists of macros for titles, section headers,
     displays and lists. Essentially items which affect the physical position
     of text on a formatted page.  In addition to the page structure domain,
     there are two more domains, the manual domain and the general text
     domain.  The general text domain is defined as macros which perform tasks
     such as quoting or emphasizing pieces of text.  The manual domain is
     defined as macros that are a subset of the day to day informal language
     used to describe commands, routines and related BSD files.  Macros in the
     manual domain handle command names, command line arguments and options,
     function names, function parameters, pathnames, variables, cross
     references to other manual pages, and so on.  These domain items have
     value for both the author and the future user of the manual page.  It is
     hoped the consistency gained across the manual set will provide easier
     translation to future documentation tools.

     Throughout the UNIX manual pages, a manual entry is simply referred to as
     a man page, regardless of actual length and without sexist intention.

GETTING STARTED

     Since a tutorial document is normally read when a person desires to use
     the material immediately, the assumption has been made that the user of
     this document may be impatient.  The material presented in the remained
     of this document is outlined as follows:

           1.   TROFF IDIOSYNCRASIES
                      Macro Usage.
                      Passing Space Characters in an Argument.
                      Trailing Blank Space Characters (a warning).
                      Escaping Special Characters.

           2.   THE ANATOMY OF A MAN PAGE
                      A manual page template.

           3.   TITLE MACROS.

           4.   INTRODUCTION OF MANUAL AND GENERAL TEXT DOMAINS.
                      What’s in a name....
                      General Syntax.

           5.   MANUAL DOMAIN
                      Addresses.
                      Author name.
                      Arguments.
                      Configuration Declarations (section four only).
                      Command Modifier.
                      Defined Variables.
                      Errno’s (Section two only).
                      Environment Variables.
                      Function Argument.
                      Function Declaration.
                      Flags.
                      Functions (library routines).
                      Function Types.
                      Interactive Commands.
                      Names.
                      Options.
                      Pathnames.
                      Variables.
                      Cross References.

           6.   GENERAL TEXT DOMAIN
                      AT&T Macro.
                      BSD Macro.
                      FreeBSD Macro.
                      UNIX Macro.
                      Enclosure/Quoting Macros
                                  Angle Bracket Quote/Enclosure.
                                  Bracket Quotes/Enclosure.
                                  Double Quote macro/Enclosure.
                                  Parenthesis Quote/Enclosure.
                                  Single Quotes/Enclosure.
                                  Prefix Macro.
                      No-Op or Normal Text Macro.
                      No Space Macro.
                      Section Cross References.
                      References and Citations.
                      Return Values (sections two and three only)
                      Trade Names (Acronyms and Type Names).
                      Extended  Arguments.

           7.   PAGE STRUCTURE DOMAIN
                      Section Headers.
                      Paragraphs and Line Spacing.
                      Keeps.
                      Displays.
                      Font Modes (Emphasis, Literal, and Symbolic).
                      Lists and Columns.

           8.   PREDEFINED STRINGS

           9.   DIAGNOSTICS

           10.  FORMATTING WITH GROFF, TROFF AND NROFF

           11.  BUGS

TROFF IDIOSYNCRASIES

     The -mdoc package attempts to simplify the process of writing a man page.
     Theoretically, one should not have to learn the dirty details of troff(1)
     to use -mdoc; however, there are a few limitations which are unavoidable
     and best gotten out of the way.  And, too, be forewarned, this package is
     not fast.

   Macro Usage
     As in troff(1), a macro is called by placing a ‘.’ (dot character) at the
     beginning of a line followed by the two character name for the macro.
     Arguments may follow the macro separated by spaces.  It is the dot
     character at the beginning of the line which causes troff(1) to interpret
     the next two characters as a macro name.  To place a ‘.’ (dot character)
     at the beginning of a line in some context other than a macro invocation,
     precede the ‘.’ (dot) with the ‘\&’ escape sequence.  The ‘\&’ translates
     literally to a zero width space, and is never displayed in the output.

     In general, troff(1) macros accept up to nine arguments, any extra
     arguments are ignored.  Most macros in -mdoc accept nine arguments and,
     in limited cases, arguments may be continued or extended on the next line
     (See Extensions).  A few macros handle quoted arguments (see Passing
     Space Characters in an Argument below).

     Most of the -mdoc general text domain and manual domain macros are
     special in that their argument lists are parsed for callable macro names.
     This means an argument on the argument list which matches a general text
     or manual domain macro name and is determined to be callable will be
     executed or called when it is processed.  In this case the argument,
     although the name of a macro, is not preceded by a ‘.’ (dot).  It is in
     this manner that many macros are nested; for example the option macro,
     ‘.Op’, may call the flag and argument macros, ‘Fl’ and ‘Ar’, to specify
     an optional flag with an argument:

           [-s bytes]         is produced by .Op Fl s Ar bytes

     To prevent a two character string from being interpreted as a macro name,
     precede the string with the escape sequence ‘\&’:

           [Fl s Ar bytes]    is produced by .Op \&Fl s \&Ar bytes

     Here the strings ‘Fl’ and ‘Ar’ are not interpreted as macros.  Macros
     whose argument lists are parsed for callable arguments are referred to as
     parsed and macros which may be called from an argument list are referred
     to as callable throughout this document and in the companion quick
     reference manual mdoc(7).  This is a technical faux pas as almost all of
     the macros in -mdoc are parsed, but as it was cumbersome to constantly
     refer to macros as being callable and being able to call other macros,
     the term parsed has been used.

   Passing Space Characters in an Argument
     Sometimes it is desirable to give as one argument a string containing one
     or more blank space characters.  This may be necessary to defeat the nine
     argument limit or to specify arguments to macros which expect particular
     arrangement of items in the argument list.  For example, the function
     macro ‘.Fn’ expects the first argument to be the name of a function and
     any remaining arguments to be function parameters.  As ANSI C stipulates
     the declaration of function parameters in the parenthesized parameter
     list, each parameter is guaranteed to be at minimum a two word string.
     For example, int foo.

     There are two possible ways to pass an argument which contains an
     embedded space.  Implementation note: Unfortunately, the most convenient
     way of passing spaces in between quotes by reassigning individual
     arguments before parsing was fairly expensive speed wise and space wise
     to implement in all the macros for AT&T troff.  It is not expensive for
     groff but for the sake of portability, has been limited to the following
     macros which need it the most:

           Cd    Configuration declaration (section 4 SYNOPSIS)
           Bl    Begin list (for the width specifier).
           Em    Emphasized text.
           Fn    Functions (sections two and four).
           It    List items.
           Li    Literal text.
           Sy    Symbolic text.
           %B    Book titles.
           %J    Journal names.
           %O    Optional notes for a reference.
           %R    Report title (in a reference).
           %T    Title of article in a book or journal.

     One way of passing a string containing blank spaces is to use the hard or
     unpaddable space character ‘\ ’, that is, a blank space preceded by the
     escape character ‘\’.  This method may be used with any macro but has the
     side effect of interfering with the adjustment of text over the length of
     a line.  Troff sees the hard space as if it were any other printable
     character and cannot split the string into blank or newline separated
     pieces as one would expect.  The method is useful for strings which are
     not expected to overlap a line boundary.  For example:

           fetch(char *str)  is created by ‘.Fn fetch char\ *str’

           fetch(char *str)  can also be created by ‘.Fn fetch "char *str"’

     If the ‘\’ or quotes were omitted, ‘.Fn’ would see three arguments and
     the result would be:

           fetch(char, *str)

     For an example of what happens when the parameter list overlaps a newline
     boundary, see the BUGS section.

   Trailing Blank Space Characters
     Troff can be confused by blank space characters at the end of a line.  It
     is a wise preventive measure to globally remove all blank spaces from
     <blank-space><end-of-line> character sequences.  Should the need arise to
     force a blank character at the end of a line, it may be forced with an
     unpaddable space and the ‘\&’ escape character.  For example,
     ‘string\ \&’.

   Escaping Special Characters
     Special characters like the newline character ‘\n’, are handled by
     replacing the ‘\’ with ‘\e’ (e.g.  ‘\en’) to preserve the backslash.

THE ANATOMY OF A MAN PAGE

     The body of a man page is easily constructed from a basic template found
     in the file /usr/share/misc/mdoc.template.  Several example man pages can
     also be found in /usr/share/examples/mdoc.

   A manual page template
           .\" The following requests are required for all man pages.
           .Dd Month day, year
           .Os OPERATING_SYSTEM [version/release]
           .Dt DOCUMENT_TITLE [section number] [volume]
           .Sh NAME
           .Nm name
           .Nd one line description of name
           .Sh SYNOPSIS
           .Sh DESCRIPTION
           .\" The following requests should be uncommented and
           .\" used where appropriate.  This next request is
           .\" for sections 2 and 3 function return values only.
           .\" .Sh RETURN VALUES
           .\" This next request is for sections 1, 6, 7 & 8 only
           .\" .Sh ENVIRONMENT
           .\" .Sh FILES
           .\" .Sh EXAMPLES
           .\" This next request is for sections 1, 6, 7 & 8 only
           .\"     (command return values (to shell) and
           .\"       fprintf/stderr type diagnostics)
           .\" .Sh DIAGNOSTICS
           .\" The next request is for sections 2 and 3 error
           .\" and signal handling only.
           .\" .Sh ERRORS
           .\" .Sh SEE ALSO
           .\" .Sh STANDARDS
           .\" .Sh HISTORY
           .\" .Sh AUTHORS
           .\" .Sh BUGS

     The first items in the template are the macros (.Dd, .Os, .Dt); the
     document date, the operating system the man page or subject source is
     developed or modified for, and the man page title (in upper case) along
     with the section of the manual the page belongs in.  These macros
     identify the page, and are discussed below in TITLE MACROS.

     The remaining items in the template are section headers (.Sh); of which
     NAME, SYNOPSIS and DESCRIPTION are mandatory.  The headers are discussed
     in PAGE STRUCTURE DOMAIN, after presentation of MANUAL DOMAIN.  Several
     content macros are used to demonstrate page layout macros; reading about
     content macros before page layout macros is recommended.

TITLE MACROS

     The title macros are the first portion of the page structure domain, but
     are presented first and separate for someone who wishes to start writing
     a man page yesterday.  Three header macros designate the document title
     or manual page title, the operating system, and the date of authorship.
     These macros are one called once at the very beginning of the document
     and are used to construct the headers and footers only.

     .Dt DOCUMENT_TITLE section# [volume]
             The document title is the subject of the man page and must be in
             CAPITALS due to troff limitations.  The section number may be
             1, ..., 8, and if it is specified, the volume title may be
             omitted.  A volume title may be arbitrary or one of the
             following:

                   AMD    UNIX Ancestral Manual Documents
                   SMM    UNIX System Manager’s Manual
                   URM    UNIX Reference Manual
                   PRM    UNIX Programmer’s Manual

             The default volume labeling is URM for sections 1, 6, and 7; SMM
             for section 8; PRM for sections 2, 3, 4, and 5.

     .Os operating_system release#
             The name of the operating system should be the common acronym,
             e.g.  BSD or FreeBSD or ATT.  The release should be the standard
             release nomenclature for the system specified, e.g. 4.3,
             4.3+Tahoe, V.3, V.4.  Unrecognized arguments are displayed as
             given in the page footer.  For instance, a typical footer might
             be:

                   .Os BSD 4.3

             or
                   .Os FreeBSD 2.2

             or for a locally produced set

                   .Os CS Department

             The Berkeley default, ‘.Os’ without an argument, has been defined
             as BSD in the site specific file /usr/share/tmac/mdoc/doc-common.
             It really should default to LOCAL.  Note, if the ‘.Os’ macro is
             not present, the bottom left corner of the page will be ugly.

     .Dd month day, year
             The date should be written formally:

                   January 25, 1989

INTRODUCTION OF MANUAL AND GENERAL TEXT DOMAINS

   Whats in a name...
     The manual domain macro names are derived from the day to day informal
     language used to describe commands, subroutines and related files.
     Slightly different variations of this language are used to describe the
     three different aspects of writing a man page.  First, there is the
     description of -mdoc macro request usage.  Second is the description of a
     UNIX command with -mdoc macros and third, the description of a command to
     a user in the verbal sense; that is, discussion of a command in the text
     of a man page.

     In the first case, troff(1) macros are themselves a type of command; the
     general syntax for a troff command is:

           .Va argument1 argument2 ... argument9

     The ‘.Va’ is a macro command or request, and anything following it is an
     argument to be processed.  In the second case, the description of a UNIX
     command using the content macros is a bit more involved; a typical
     SYNOPSIS command line might be displayed as:

           filter [-flag] infile outfile

     Here, filter is the command name and the bracketed string -flag is a flag
     argument designated as optional by the option brackets.  In -mdoc terms,
     infile and outfile are called arguments.  The macros which formatted the
     above example:

           .Nm filter
           .Op Fl flag
           .Ar infile outfile

     In the third case, discussion of commands and command syntax includes
     both examples above, but may add more detail.  The arguments infile and
     outfile from the example above might be referred to as operands or file
     arguments.  Some command line argument lists are quite long:

           make  [-eiknqrstv] [-D variable] [-d flags] [-f makefile]
                 [-I directory] [-j max_jobs] [variable=value] [target ...]

     Here one might talk about the command make and qualify the argument
     makefile, as an argument to the flag, -f, or discuss the optional file
     operand target.  In the verbal context, such detail can prevent
     confusion, however the -mdoc package does not have a macro for an
     argument to a flag.  Instead the ‘Ar’ argument macro is used for an
     operand or file argument like target as well as an argument to a flag
     like variable.  The make command line was produced from:

           .Nm make
           .Op Fl eiknqrstv
           .Op Fl D Ar variable
           .Op Fl d Ar flags
           .Op Fl f Ar makefile
           .Op Fl I Ar directory
           .Op Fl j Ar max_jobs
           .Op Ar variable=value
           .Bk -words
           .Op Ar target ...
           .Ek

     The ‘.Bk’ and ‘.Ek’ macros are explained in Keeps.

   General Syntax
     The manual domain and general text domain macros share a similar syntax
     with a few minor deviations: ‘.Ar’, ‘.Fl’, ‘.Nm’, and ‘.Pa’ differ only
     when called without arguments; ‘.Fn’ and ‘.Xr’ impose an order on their
     argument lists and the ‘.Op’ and ‘.Fn’ macros have nesting limitations.
     All content macros are capable of recognizing and properly handling
     punctuation, provided each punctuation character is separated by a
     leading space.  If an request is given:

           .Li sptr, ptr),

     The result is:

           sptr, ptr),

     The punctuation is not recognized and all is output in the literal font.
     If the punctuation is separated by a leading white space:

           .Li sptr , ptr ) ,

     The result is:

           sptr, ptr),

     The punctuation is now recognized and is output in the default font
     distinguishing it from the strings in literal font.

     To remove the special meaning from a punctuation character escape it with
     ‘\&’.  Troff is limited as a macro language, and has difficulty when
     presented with a string containing a member of the mathematical, logical
     or quotation set:

                 {+,-,/,*,%,<,>,<=,>=,=,==,&,‘,’,"}

     The problem is that troff may assume it is supposed to actually perform
     the operation or evaluation suggested by the characters.  To prevent the
     accidental evaluation of these characters, escape them with ‘\&’.
     Typical syntax is shown in the first content macro displayed below,
     ‘.Ad’.

MANUAL DOMAIN

   Address Macro
     The address macro identifies an address construct of the form
     addr1[,addr2[,addr3]].

           Usage: .Ad address ...
                   .Ad addr1    addr1
                   .Ad addr1 .  addr1.
                   .Ad addr1 , file2
                                addr1, file2
                   .Ad f1 , f2 , f3 :
                                f1, f2, f3:
                   .Ad addr ) ) ,
                                addr)),

     It is an error to call ‘.Ad’ without arguments.  ‘.Ad’ is callable by
     other macros and is parsed.

   Author Name
     The ‘.An’ macro is used to specify the name of the author of the item
     being documented, or the name of the author of the actual manual page.
     Any remaining arguments after the name information are assumed to be
     punctuation.

           Usage: .An author_name
                   .An Joe Author
                                  Joe Author
                   .An Joe Author ,
                                  Joe Author,
                   .An Joe Author Aq nobody@FreeBSD.ORG
                                  Joe Author 〈nobody@FreeBSD.ORG〉
                   .An Joe Author ) ) ,
                                  Joe Author)),

     The ‘.An’ macro is parsed and is callable.  It is an error to call ‘.An’
     without any arguments.

   Argument Macro
     The ‘.Ar’ argument macro may be used whenever a command line argument is
     referenced.

           Usage: .Ar argument ...
                    .Ar          file ...
                    .Ar file1    file1
                    .Ar file1 .  file1.
                    .Ar file1 file2
                                 file1 file2
                    .Ar f1 f2 f3 :
                                 f1 f2 f3:
                    .Ar file ) ) ,
                                 file)),

     If ‘.Ar’ is called without arguments ‘file ...’ is assumed.  The ‘.Ar’
     macro is parsed and is callable.

   Configuration Declaration (section four only)
     The ‘.Cd’ macro is used to demonstrate a config(8) declaration for a
     device interface in a section four manual.  This macro accepts quoted
     arguments (double quotes only).

           device le0 at scode?  produced by: ‘.Cd device le0 at scode?’.

   Command Modifier
     The command modifier is identical to the ‘.Fl’ (flag) command with the
     exception the ‘.Cm’ macro does not assert a dash in front of every
     argument.  Traditionally flags are marked by the preceding dash, some
     commands or subsets of commands do not use them.  Command modifiers may
     also be specified in conjunction with interactive commands such as editor
     commands.  See Flags.

   Defined Variables
     A variable which is defined in an include file is specified by the macro
     ‘.Dv’.

           Usage: .Dv defined_variable ...
                   .Dv MAXHOSTNAMELEN
                                   MAXHOSTNAMELEN
                   .Dv TIOCGPGRP )
                                   TIOCGPGRP)

     It is an error to call ‘.Dv’ without arguments.  ‘.Dv’ is parsed and is
     callable.

   Errnos (Section two only)
     The ‘.Er’ errno macro specifies the error return value for section two
     library routines.  The second example below shows ‘.Er’ used with the
     ‘.Bq’ general text domain macro, as it would be used in a section two
     manual page.

           Usage: .Er ERRNOTYPE ...
                   .Er ENOENT
                              ENOENT
                   .Er ENOENT ) ;
                              ENOENT);
                   .Bq Er ENOTDIR
                              [ENOTDIR]

     It is an error to call ‘.Er’ without arguments.  The ‘.Er’ macro is
     parsed and is callable.

   Environment Variables
     The ‘.Ev’ macro specifies an environment variable.

           Usage: .Ev argument ...
                   .Ev DISPLAY
                               DISPLAY
                   .Ev PATH .  PATH.
                   .Ev PRINTER ) ) ,
                               PRINTER)),

     It is an error to call ‘.Ev’ without arguments.  The ‘.Ev’ macro is
     parsed and is callable.

   Function Argument
     The ‘.Fa’ macro is used to refer to function arguments (parameters)
     outside of the SYNOPSIS section of the manual or inside the SYNOPSIS
     section should a parameter list be too long for the ‘.Fn’ macro and the
     enclosure macros ‘.Fo’ and ‘.Fc’ must be used.  ‘.Fa’ may also be used to
     refer to structure members.

           Usage: .Fa function_argument ...
                   .Fa d_namlen ) ) ,
                                   d_namlen)),
                   .Fa iov_len     iov_len

     It is an error to call ‘.Fa’ without arguments.  ‘.Fa’ is parsed and is
     callable.

   Function Declaration
     The ‘.Fd’ macro is used in the SYNOPSIS section with section two or three
     functions.  The ‘.Fd’ macro does not call other macros and is not
     callable by other macros.

           Usage: .Fd include_file (or defined variable)

     In the SYNOPSIS section a ‘.Fd’ request causes a line break if a function
     has already been presented and a break has not occurred.  This leaves a
     nice vertical space in between the previous function call and the
     declaration for the next function.

   Flags
     The ‘.Fl’ macro handles command line flags.  It prepends a dash, ‘-’, to
     the flag.  For interactive command flags, which are not prepended with a
     dash, the ‘.Cm’ (command modifier) macro is identical, but without the
     dash.

           Usage: .Fl argument ...
                   .Fl          -
                   .Fl cfv      -cfv
                   .Fl cfv .    -cfv.
                   .Fl s v t    -s -v -t
                   .Fl - ,      --,
                   .Fl xyz ) ,  -xyz),

     The ‘.Fl’ macro without any arguments results in a dash representing
     stdin/stdout.  Note that giving ‘.Fl’ a single dash, will result in two
     dashes.  The ‘.Fl’ macro is parsed and is callable.

   Functions (library routines)
     The .Fn macro is modeled on ANSI C conventions.

     Usage: .Fn [type] function [[type] parameters ... ]
     .Fn getchar                          getchar()
     .Fn strlen ) ,                       strlen()),
     .Fn "int align" "const * char *sptrs",
                                          int align(const * char *sptrs),

     It is an error to call ‘.Fn’ without any arguments.  The ‘.Fn’ macro is
     parsed and is callable, note that any call to another macro signals the
     end of the ‘.Fn’ call (it will close-parenthesis at that point).

     For functions that have more than eight parameters (and this is rare),
     the macros ‘.Fo’ (function open) and ‘.Fc’ (function close) may be used
     with ‘.Fa’ (function argument) to get around the limitation. For example:

           .Fo "int res_mkquery"
           .Fa "int op"
           .Fa "char *dname"
           .Fa "int class"
           .Fa "int type"
           .Fa "char *data"
           .Fa "int datalen"
           .Fa "struct rrec *newrr"
           .Fa "char *buf"
           .Fa "int buflen"
           .Fc

     Produces:

           int   res_mkquery(int op,   char *dname,    int class,    int type,
           char *data, int datalen, struct rrec *newrr, char *buf, int buflen)

     The ‘.Fo’ and ‘.Fc’ macros are parsed and are callable.  In the SYNOPSIS
     section, the function will always begin at the beginning of line.  If
     there is more than one function presented in the SYNOPSIS section and a
     function type has not been given, a line break will occur, leaving a nice
     vertical space between the current function name and the one prior.  At
     the moment, ‘.Fn’ does not check its word boundaries against troff line
     lengths and may split across a newline ungracefully.  This will be fixed
     in the near future.

   Function Type
     This macro is intended for the SYNOPSIS section.  It may be used anywhere
     else in the man page without problems, but its main purpose is to present
     the function type in kernel normal form for the SYNOPSIS of sections two
     and three (it causes a line break allowing the function name to appear on
     the next line).

           Usage: .Ft type ...
                   .Ft struct stat  struct stat

     The ‘.Ft’ request is not callable by other macros.

   Interactive Commands
     The ‘.Ic’ macro designates an interactive or internal command.

           Usage: .Ic argument ...
                   .Ic :wq             :wq
                   .Ic do while {...}  do while {...}
                   .Ic setenv , unsetenv
                                       setenv, unsetenv

     It is an error to call ‘.Ic’ without arguments.  The ‘.Ic’ macro is
     parsed and is callable.

   Name Macro
     The ‘.Nm’ macro is used for the document title or subject name.  It has
     the peculiarity of remembering the first argument it was called with,
     which should always be the subject name of the page.  When called without
     arguments, ‘.Nm’ regurgitates this initial name for the sole purpose of
     making less work for the author.  Note: a section two or three document
     function name is addressed with the ‘.Nm’ in the NAME section, and with
     ‘.Fn’ in the SYNOPSIS and remaining sections.  For interactive commands,
     such as the ‘while’ command keyword in csh(1), the ‘.Ic’ macro should be
     used.  While the ‘.Ic’ is nearly identical to ‘.Nm’, it can not recall
     the first argument it was invoked with.

           Usage: .Nm argument ...
                   .Nm mdoc.sample
                                mdoc.sample
                   .Nm \-mdoc   -mdoc.
                   .Nm foo ) ) ,
                                foo)),
                   .Nm          mdoc.samples

     The ‘.Nm’ macro is parsed and is callable.

   Options
     The ‘.Op’ macro places option brackets around the any remaining arguments
     on the command line, and places any trailing punctuation outside the
     brackets.  The macros ‘.Oc’ and ‘.Oo’ may be used across one or more
     lines.

           Usage: .Op options ...
           .Op                    []
           .Op Fl k               [-k]
           .Op Fl k ) .           [-k]).
           .Op Fl k Ar kookfile   [-k kookfile]
           .Op Fl k Ar kookfile ,
                                  [-k kookfile],
           .Op Ar objfil Op Ar corfil
                                  [objfil [corfil]]
           .Op Fl c Ar objfil Op Ar corfil ,
                                  [-c objfil [corfil]],
           .Op word1 word2        [word1 word2]

     The ‘.Oc’ and ‘.Oo’ macros:

           .Oo
           .Op Fl k Ar kilobytes
           .Op Fl i Ar interval
           .Op Fl c Ar count
           .Oc

     Produce: [[-k kilobytes] [-i interval] [-c count]]

     The macros ‘.Op’, ‘.Oc’ and ‘.Oo’ are parsed and are callable.

   Pathnames
     The ‘.Pa’ macro formats path or file names.

           Usage: .Pa pathname
                   .Pa /usr/share   /usr/share
                   .Pa /tmp/fooXXXXX ) .
                                    /tmp/fooXXXXX).

     The ‘.Pa’ macro is parsed and is callable.

   Variables
     Generic variable reference:

           Usage: .Va variable ...
                   .Va count   count
                   .Va settimer,
                               settimer,
                   .Va int *prt ) :
                               int *prt):
                   .Va char s ] ) ) ,
                               char s])),

     It is an error to call ‘.Va’ without any arguments.  The ‘.Va’ macro is
     parsed and is callable.

   Manual Page Cross References
     The ‘.Xr’ macro expects the first argument to be a manual page name, and
     the second argument, if it exists, to be either a section page number or
     punctuation.  Any remaining arguments are assumed to be punctuation.

           Usage: .Xr man_page [1,...,8]
                   .Xr mdoc    mdoc
                   .Xr mdoc ,  mdoc,
                   .Xr mdoc 7  mdoc(7)
                   .Xr mdoc 7 ) ) ,
                               mdoc(7))),

     The ‘.Xr’ macro is parsed and is callable.  It is an error to call ‘.Xr’
     without any arguments.

GENERAL TEXT DOMAIN

   AT&T Macro
           Usage: .At [v6 | v7 | 32v | V.1 | V.4] ...
                   .At                    AT&T UNIX
                   .At v6 .               Version 6 AT&T UNIX.

     The ‘.At’ macro is not parsed and not callable. It accepts at most two
     arguments.

   BSD Macro
           Usage: .Bx [Version/release] ...
                   .Bx       BSD
                   .Bx 4.3 .
                             4.3BSD.

     The ‘.Bx’ macro is parsed and is callable.

   FreeBSD Macro
           Usage: .Fx Version.release ...
                   .Fx 2.2 .      FreeBSD 2.2.

     The ‘.Fx’ macro is not parsed and not callable. It accepts at most two
     arguments.

   UNIX Macro
           Usage: .Ux ...
                   .Ux         UNIX

     The ‘.Ux’ macro is parsed and is callable.

   Enclosure and Quoting Macros
     The concept of enclosure is similar to quoting.  The object being to
     enclose one or more strings between a pair of characters like quotes or
     parentheses.  The terms quoting and enclosure are used interchangeably
     throughout this document.  Most of the one line enclosure macros end in
     small letter ‘q’ to give a hint of quoting, but there are a few
     irregularities.  For each enclosure macro there is also a pair of open
     and close macros which end in small letters ‘o’ and ‘c’ respectively.
     These can be used across one or more lines of text and while they have
     nesting limitations, the one line quote macros can be used inside of
     them.

            Quote    Close    Open   Function                  Result
           .Aq      .Ac      .Ao     Angle Bracket Enclosure   <string>
           .Bq      .Bc      .Bo     Bracket Enclosure         [string]
           .Dq      .Dc      .Do     Double Quote              ‘‘string’’
                    .Ec      .Eo     Enclose String (in XX)    XXstringXX
           .Pq      .Pc      .Po     Parenthesis Enclosure     (string)
           .Ql                       Quoted Literal            ‘st’ or string
           .Qq      .Qc      .Qo     Straight Double Quote     "string"
           .Sq      .Sc      .So     Single Quote              ‘string’

     Except for the irregular macros noted below, all of the quoting macros
     are parsed and callable.  All handle punctuation properly, as long as it
     is presented one character at a time and separated by spaces.  The
     quoting macros examine opening and closing punctuation to determine
     whether it comes before or after the enclosing string. This makes some
     nesting possible.

     .Ec, .Eo  These macros expect the first argument to be the opening and
               closing strings respectively.

     .Ql       The quoted literal macro behaves differently for troff than
               nroff.  If formatted with nroff, a quoted literal is always
               quoted. If formatted with troff, an item is only quoted if the
               width of the item is less than three constant width characters.
               This is to make short strings more visible where the font
               change to literal (constant width) is less noticeable.

     .Pf       The prefix macro is not callable, but it is parsed:

                     .Pf ( Fa name2
                              becomes (name2.

               The ‘.Ns’ (no space) macro performs the analogous suffix
               function.

     Examples of quoting:
           .Aq                   〈〉
           .Aq Ar ctype.h ) ,    〈ctype.h〉),
           .Bq                   []
           .Bq Em Greek , French .
                                 [Greek, French].
           .Dq                   “”
           .Dq string abc .      “string abc”.
           .Dq ´^[A-Z]´          “´^[A-Z]´”
           .Ql man mdoc          ‘man mdoc’
           .Qq                   ""
           .Qq string ) ,        "string"),
           .Qq string Ns ),      "string),"
           .Sq                   ‘’
           .Sq string            ‘string’

     For a good example of nested enclosure macros, see the ‘.Op’ option
     macro.  It was created from the same underlying enclosure macros as those
     presented in the list above.  The ‘.Xo’ and ‘.Xc’ extended argument list
     macros were also built from the same underlying routines and are a good
     example of -mdoc macro usage at its worst.

   No-Op or Normal Text Macro
     The macro ‘.No’ is a hack for words in a macro command line which should
     not be formatted and follows the conventional syntax for content macros.

   Space Macro
     The ‘.Ns’ macro eliminates unwanted spaces in between macro requests.  It
     is useful for old style argument lists where there is no space between
     the flag and argument:

           .Op Fl I Ns Ar directory
                            produces [-Idirectory]

     Note: the ‘.Ns’ macro always invokes the ‘.No’ macro after eliminating
     the space unless another macro name follows it.  The macro ‘.Ns’ is
     parsed and is callable.

   Section Cross References
     The ‘.Sx’ macro designates a reference to a section header within the
     same document.  It is parsed and is callable.

                   .Sx FILES     FILES

   References and Citations
     The following macros make a modest attempt to handle references.  At
     best, the macros make it convenient to manually drop in a subset of refer
     style references.

           .Rs     Reference Start.  Causes a line break and begins collection
                   of reference information until the reference end macro is
                   read.
           .Re     Reference End.  The reference is printed.
           .%A     Reference author name, one name per invocation.
           .%B     Book title.
           .%C     City/place.
           .%D     Date.
           .%J     Journal name.
           .%N     Issue number.
           .%O     Optional information.
           .%P     Page number.
           .%R     Report name.
           .%T     Title of article.
           .%V     Volume(s).

     The macros beginning with ‘%’ are not callable, and are parsed only for
     the trade name macro which returns to its caller.  (And not very
     predictably at the moment either.)  The purpose is to allow trade names
     to be pretty printed in troff/ditroff output.

   Return Values
     The ‘.Rv’ macro generates text for use in the RETURN VALUES section.

           Usage: .Rv [-std function]

     ‘.Rv -std atexit’ will generate the following text:

     The atexit() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

     The -std option is valid only for manual page sections 2 and 3.

   Trade Names (or Acronyms and Type Names)
     The trade name macro is generally a small caps macro for all upper case
     words longer than two characters.

           Usage: .Tn symbol ...
                   .Tn DEC
                          DEC
                   .Tn ASCII
                          ASCII

     The ‘.Tn’ macro is parsed and is callable by other macros.

   Extended Arguments
     The ‘.Xo’ and ‘.Xc’ macros allow one to extend an argument list on a
     macro boundary.  Argument lists cannot be extended within a macro which
     expects all of its arguments on one line such as ‘.Op’.

     Here is an example of ‘.Xo’ using the space mode macro to turn spacing
     off:

           .Sm off
           .It Xo Sy I Ar operation
           .No \en Ar count No \en
           .Xc
           .Sm on

     Produces

           Ioperation\ncount\n

     Another one:

           .Sm off
           .It Cm S No / Ar old_pattern Xo
           .No / Ar new_pattern
           .No / Op Cm g
           .Xc
           .Sm on

     Produces

           S/old_pattern/new_pattern/[g]

     Another example of ‘.Xo’ and using enclosure macros: Test the value of an
     variable.

           .It Xo
           .Ic .ifndef
           .Oo \&! Oc Ns Ar variable
           .Op Ar operator variable ...
           .Xc

     Produces

           .ifndef [!]variable [operator variable ...]

     All of the above examples have used the ‘.Xo’ macro on the argument list
     of the ‘.It’ (list-item) macro.  The extend macros are not used very
     often, and when they are it is usually to extend the list-item argument
     list.  Unfortunately, this is also where the extend macros are the most
     finicky.  In the first two examples, spacing was turned off; in the
     third, spacing was desired in part of the output but not all of it.  To
     make these macros work in this situation make sure the ‘.Xo’ and ‘.Xc’
     macros are placed as shown in the third example.  If the ‘.Xo’ macro is
     not alone on the ‘.It’ argument list, spacing will be unpredictable.  The
     ‘.Ns’ (no space macro) must not occur as the first or last macro on a
     line in this situation.  Out of 900 manual pages (about 1500 actual
     pages) currently released with BSD only fifteen use the ‘.Xo’ macro.

PAGE STRUCTURE DOMAIN

   Section Headers
     The first three ‘.Sh’ section header macros list below are required in
     every man page.  The remaining section headers are recommended at the
     discretion of the author writing the manual page.  The ‘.Sh’ macro can
     take up to nine arguments.  It is parsed and but is not callable.

     .Sh NAME  The ‘.Sh NAME’ macro is mandatory.  If not specified, the
               headers, footers and page layout defaults will not be set and
               things will be rather unpleasant.  The NAME section consists of
               at least three items.  The first is the ‘.Nm’ name macro naming
               the subject of the man page.  The second is the Name
               Description macro, ‘.Nd’, which separates the subject name from
               the third item, which is the description.  The description
               should be the most terse and lucid possible, as the space
               available is small.

     .Sh SYNOPSIS
               The SYNOPSIS section describes the typical usage of the subject
               of a man page.  The  macros required are either ‘.Nm’, ‘.Cd’,
               ‘.Fn’, (and possibly ‘.Fo’, ‘.Fc’, ‘.Fd’, ‘.Ft’ macros).  The
               function name macro ‘.Fn’ is required for manual page sections
               2 and 3, the command and general name macro ‘.Nm’ is required
               for sections 1, 5, 6, 7, 8.  Section 4 manuals require a ‘.Nm’,
               ‘.Fd’ or a ‘.Cd’ configuration device usage macro.  Several
               other macros may be necessary to produce the synopsis line as
               shown below:

                     cat [-benstuv] [-] file ...

               The following macros were used:

                     .Nm cat
                     .Op Fl benstuv
                     .Op Fl
                     .Ar

               Note: The macros ‘.Op’, ‘.Fl’, and ‘.Ar’ recognize the pipe bar
               character ‘|’, so a command line such as:

                     .Op Fl a | Fl b

               will not go orbital.  Troff normally interprets a | as a
               special operator.  See PREDEFINED STRINGS for a usable |
               character in other situations.

     .Sh DESCRIPTION
               In most cases the first text in the DESCRIPTION section is a
               brief paragraph on the command, function or file, followed by a
               lexical list of options and respective explanations.  To create
               such a list, the ‘.Bl’ begin-list, ‘.It’ list-item and ‘.El’
               end-list macros are used (see Lists and Columns below).

     The following ‘.Sh’ section headers are part of the preferred manual page
     layout and must be used appropriately to maintain consistency.  They are
     listed in the order in which they would be used.

     .Sh ENVIRONMENT
               The ENVIRONMENT section should reveal any related environment
               variables and clues to their behavior and/or usage.

     .Sh EXAMPLES
               There are several ways to create examples.  See the EXAMPLES
               section below for details.

     .Sh FILES
               Files which are used or created by the man page subject should
               be listed via the ‘.Pa’ macro in the FILES section.

     .Sh SEE ALSO
               References to other material on the man page topic and cross
               references to other relevant man pages should be placed in the
               SEE ALSO section.  Cross references are specified using the
               ‘.Xr’ macro.  Cross references in the SEE ALSO section should
               be sorted by section number, and then placed in alphabetical
               order and comma separated.  For example:

               ls(1), ps(1), group(5), passwd(5).

               At this time refer(1) style references are not accommodated.

     .Sh STANDARDS
               If the command, library function or file adheres to a specific
               implementation such as IEEE Std 1003.2 (“POSIX.2”) or ANSI
               X3.159-1989 (“ANSI C”) this should be noted here.  If the
               command does not adhere to any standard, its history should be
               noted in the HISTORY section.

     .Sh HISTORY
               Any command which does not adhere to any specific standards
               should be outlined historically in this section.

     .Sh AUTHORS
               Credits, if need be, should be placed here.

     .Sh DIAGNOSTICS
               Diagnostics from a command should be placed in this section.

     .Sh ERRORS
               Specific error handling, especially from library functions (man
               page sections 2 and 3) should go here.  The ‘.Er’ macro is used
               to specify an errno.

     .Sh BUGS  Blatant problems with the topic go here...

     User specified ‘.Sh’ sections may be added, for example, this section was
     set with:

                   .Sh PAGE STRUCTURE DOMAIN

   Paragraphs and Line Spacing.
     .Pp     The ‘.Pp’ paragraph command may be used to specify a line space
             where necessary.  The macro is not necessary after a ‘.Sh’ or
             ‘.Ss’ macro or before a ‘.Bl’ macro.  (The ‘.Bl’ macro asserts a
             vertical distance unless the -compact flag is given).

   Keeps
     The only keep that is implemented at this time is for words.  The macros
     are ‘.Bk’ (begin-keep) and ‘.Ek’ (end-keep).  The only option that ‘.Bk’
     accepts is -words and is useful for preventing line breaks in the middle
     of options.  In the example for the make command line arguments (see
     Whats in a name), the keep prevented nroff from placing up the flag and
     the argument on separate lines.  (Actually, the option macro used to
     prevent this from occurring, but was dropped when the decision
     (religious) was made to force right justified margins in troff as options
     in general look atrocious when spread across a sparse line.  More work
     needs to be done with the keep macros, a -line option needs to be added.)

   Examples and Displays
     There are five types of displays, a quickie one line indented display
     ‘.D1’, a quickie one line literal display ‘.Dl’, and a block literal,
     block filled and block ragged which use the ‘.Bd’ begin-display and ‘.Ed’
     end-display macros.

     .D1    (D-one) Display one line of indented text.  This macro is parsed,
            but it is not callable.

                  -ldghfstru

            The above was produced by: .Dl -ldghfstru.

     .Dl    (D-ell) Display one line of indented literal text.  The ‘.Dl’
            example macro has been used throughout this file.  It allows the
            indent (display) of one line of text.  Its default font is set to
            constant width (literal) however it is parsed and will recognized
            other macros.  It is not callable however.

                  % ls -ldg /usr/local/bin

            The above was produced by .Dl % ls -ldg /usr/local/bin.

     .Bd    Begin-display.  The ‘.Bd’ display must be ended with the ‘.Ed’
            macro.  Displays may be nested within displays and lists.  ‘.Bd’
            has the following syntax:

                  .Bd display-type [-offset offset_value] [-compact]

            The display-type must be one of the following four types and may
            have an offset specifier for indentation: ‘.Bd’.

            -ragged           Display a block of text as typed, right (and
                              left) margin edges are left ragged.
            -filled           Display a filled (formatted) block.  The block
                              of text is formatted (the edges are filled - not
                              left unjustified).
            -literal          Display a literal block, useful for source code
                              or simple tabbed or spaced text.
            -file file_name   The file name following the -file flag is read
                              and displayed.  Literal mode is asserted and
                              tabs are set at 8 constant width character
                              intervals, however any troff/-mdoc commands in
                              file will be processed.
            -offset string    If -offset is specified with one of the
                              following strings, the string is interpreted to
                              indicate the level of indentation for the
                              forthcoming block of text:

                              left        Align block on the current left
                                          margin, this is the default mode of
                                          ‘.Bd’.
                              center      Supposedly center the block.  At
                                          this time unfortunately, the block
                                          merely gets left aligned about an
                                          imaginary center margin.
                              indent      Indents by one default indent value
                                          or tab.  The default indent value is
                                          also used for the ‘.D1’ display so
                                          one is guaranteed the two types of
                                          displays will line up.  This indent
                                          is normally set to 6n or about two
                                          thirds of an inch (six constant
                                          width characters).
                              indent-two  Indents two times the default indent
                                          value.
                              right       This left aligns the block about two
                                          inches from the right side of the
                                          page.  This macro needs work and
                                          perhaps may never do the right thing
                                          by troff.

     .Ed    End-display.

   Font Modes
     There are five macros for changing the appearance of the manual page
     text:

     .Em    Text may be stressed or emphasized with the ‘.Em’ macro.  The
            usual font for emphasis is italic.

                  Usage: .Em argument ...
                          .Em does not   does not
                          .Em exceed 1024 .
                                         exceed 1024.
                          .Em vide infra ) ) ,
                                         vide infra)),

            The ‘.Em’ macro is parsed and is callable.  It is an error to call
            ‘.Em’ without arguments.

     .Li    The ‘.Li’ literal macro may be used for special characters,
            variable constants, anything which should be displayed as it would
            be typed.

                  Usage: .Li argument ...
                          .Li \en    \n
                          .Li M1 M2 M3 ;
                                     M1 M2 M3;
                          .Li cntrl-D ) ,
                                     cntrl-D),
                          .Li 1024 ...
                                     1024 ...

            The ‘.Li’ macro is parsed and is callable.

     .Sy    The symbolic emphasis macro is generally a boldface macro in
            either the symbolic sense or the traditional English usage.

                  Usage: .Sy symbol ...
                          .Sy Important Notice
                                             Important Notice

            The ‘.Sy’ macro is parsed and is callable.  Arguments to ‘.Sy’ may
            be quoted.

     .Bf    Begin font mode.  The ‘.Bf’ font mode must be ended with the ‘.Ef’
            macro.  Font modes may be nested within other font modes.  ‘.Bf’
            has the following syntax:

                  .Bf font-mode

            The font-mode must be one of the following three types: ‘.Bf’.

            Em | -emphasis    Same as if the ‘.Em’ macro was used for the
                              entire block of text.
            Li | -literal     Same as if the ‘.Li’ macro was used for the
                              entire block of text.
            Sy | -symbolic    Same as if the ‘.Sy’ macro was used for the
                              entire block of text.

     .Ef    End font mode.

   Tagged Lists and Columns
     There are several types of lists which may be initiated with the ‘.Bl’
     begin-list macro.  Items within the list are specified with the ‘.It’
     item macro and each list must end with the ‘.El’ macro.  Lists may be
     nested within themselves and within displays.  Columns may be used inside
     of lists, but lists are unproven inside of columns.

     In addition, several list attributes may be specified such as the width
     of a tag, the list offset, and compactness (blank lines between items
     allowed or disallowed).  Most of this document has been formatted with a
     tag style list (-tag).  For a change of pace, the list-type used to
     present the list-types is an over-hanging list (-ohang).  This type of
     list is quite popular with TeX users, but might look a bit funny after
     having read many pages of tagged lists.  The following list types are
     accepted by ‘.Bl’:

     -bullet
     -item
     -enum
     These three are the simplest types of lists.  Once the ‘.Bl’ macro has
     been given, items in the list are merely indicated by a line consisting
     solely of the ‘.It’ macro.  For example, the source text for a simple
     enumerated list would look like:

                 .Bl -enum -compact
                 .It
                 Item one goes here.
                 .It
                 And item two here.
                 .It
                 Lastly item three goes here.
                 .El

     The results:

               1.   Item one goes here.
               2.   And item two here.
               3.   Lastly item three goes here.

     A simple bullet list construction:

                 .Bl -bullet -compact
                 .It
                 Bullet one goes here.
                 .It
                 Bullet two here.
                 .El

     Produces:
               ·   Bullet one goes here.
               ·   Bullet two here.

     -tag
     -diag
     -hang
     -ohang
     -inset
     These list-types collect arguments specified with the ‘.It’ macro and
     create a label which may be inset into the forthcoming text, hanged from
     the forthcoming text, overhanged from above and not indented or tagged.
     This list was constructed with the ‘-ohang’ list-type.  The ‘.It’ macro
     is parsed only for the inset, hang and tag list-types and is not
     callable.  Here is an example of inset labels:

           Tag The tagged list (also called a tagged paragraph) is the most
           common type of list used in the Berkeley manuals.

           Diag Diag lists create section four diagnostic lists and are
           similar to inset lists except callable macros are ignored.

           Hang Hanged labels are a matter of taste.

           Ohang Overhanging labels are nice when space is constrained.

           Inset Inset labels are useful for controlling blocks of paragraphs
           and are valuable for converting -mdoc manuals to other formats.

     Here is the source text which produced the above example:

           .Bl -inset -offset indent
           .It Em Tag
           The tagged list (also called a tagged paragraph) is the
           most common type of list used in the Berkeley manuals.
           .It Em Diag
           Diag lists create section four diagnostic lists
           and are similar to inset lists except callable
           macros are ignored.
           .It Em Hang
           Hanged labels are a matter of taste.
           .It Em Ohang
           Overhanging labels are nice when space is constrained.
           .It Em Inset
           Inset labels are useful for controlling blocks of
           paragraphs and are valuable for converting
           .Nm -mdoc
           manuals to other formats.
           .El

     Here is a hanged list with two items:

           Hanged  labels appear similar to tagged lists when the label is
                   smaller than the label width.

           Longer hanged list labels blend in to the paragraph unlike tagged
                   paragraph labels.

     And the unformatted text which created it:

           .Bl -hang -offset indent
           .It Em Hanged
           labels appear similar to tagged lists when the
           label is smaller than the label width.
           .It Em Longer hanged list labels
           blend in to the paragraph unlike
           tagged paragraph labels.
           .El

     The tagged list which follows uses an optional width specifier to control
     the width of the tag.

           SL      sleep time of the process (seconds blocked)
           PAGEIN  number of disk I/O’s resulting from references by the
                   process to pages not loaded in core.
           UID     numerical user-id of process owner
           PPID    numerical id of parent of process process priority (non-
                   positive when in non-interruptible wait)

     The raw text:

           .Bl -tag -width "PAGEIN" -compact -offset indent
           .It SL
           sleep time of the process (seconds blocked)
           .It PAGEIN
           number of disk
           .Tn I/O Ns ’s
           resulting from references
           by the process to pages not loaded in core.
           .It UID
           numerical user-id of process owner
           .It PPID
           numerical id of parent of process process priority
           (non-positive when in non-interruptible wait)
           .El

     Acceptable width specifiers:

           -width Fl     sets the width to the default width for a flag.  All
                         callable macros have a default width value.  The
                         ‘.Fl’, value is presently set to ten constant width
                         characters or about five sixth of an inch.

           -width 24n    sets the width to 24 constant width characters or
                         about two inches.  The ‘n’ is absolutely necessary
                         for the scaling to work correctly.

           -width ENAMETOOLONG
                         sets width to the constant width length of the string
                         given.

           -width "int mkfifo"
                         again, the width is set to the constant width of the
                         string given.

     If a width is not specified for the tag list type, the first time ‘.It’
     is invoked, an attempt is made to determine an appropriate width.  If the
     first argument to ‘.It’ is a callable macro, the default width for that
     macro will be used as if the macro name had been supplied as the width.
     However, if another item in the list is given with a different callable
     macro name, a new and nested list is assumed.

PREDEFINED STRINGS

     The following strings are predefined as may be used by preceding with the
     troff string interpreting sequence ‘\*(xx’ where xx is the name of the
     defined string or as ‘\*x’ where x is the name of the string.  The
     interpreting sequence may be used any where in the text.

           String     Nroff     Troff
           <=         <=        ≤
           >=         >=        ≥
           Rq         ’’        ”
           Lq         ‘‘        “
           ua         ^         ⇑
           aa         ’         ´
           ga         `         `
           q          "         "
           Pi         pi        π
           Ne         !=        ≠
           Le         <=        ≤
           Ge         >=        ≥
           Lt         <         >
           Gt         >         <
           Pm         +-        ±
           If         infinity  ∞
           Na         NaN       NaN
           Ba         |         |

     Note: The string named ‘q’ should be written as ‘\*q’ since it is only
     one char.

DIAGNOSTICS

     The debugging facilities for -mdoc are limited, but can help detect
     subtle errors such as the collision of an argument name with an internal
     register or macro name.  (A what?)  A register is an arithmetic storage
     class for troff with a one or two character name.  All registers internal
     to -mdoc for troff and ditroff are two characters and of the form
     <upper_case><lower_case> such as ‘Ar’, <lower_case><upper_case> as ‘aR’
     or <upper or lower letter><digit> as ‘C1’.  And adding to the muddle,
     troff has its own internal registers all of which are either two lower
     case characters or a dot plus a letter or meta-character character.  In
     one of the introduction examples, it was shown how to prevent the
     interpretation of a macro name with the escape sequence ‘\&’.  This is
     sufficient for the internal register names also.

     If a non-escaped register name is given in the argument list of a request
     unpredictable behavior will occur.  In general, any time huge portions of
     text do not appear where expected in the output, or small strings such as
     list tags disappear, chances are there is a misunderstanding about an
     argument type in the argument list.  Your mother never intended for you
     to remember this evil stuff - so here is a way to find out whether or not
     your arguments are valid: The ‘.Db’ (debug) macro displays the
     interpretation of the argument list for most macros.  Macros such as the
     ‘.Pp’ (paragraph) macro do not contain debugging information.  All of the
     callable macros do, and it is strongly advised whenever in doubt, turn on
     the ‘.Db’ macro.

           Usage: .Db [on | off]

     An example of a portion of text with the debug macro placed above and
     below an artificially created problem (a flag argument ‘aC’ which should
     be ‘\&aC’ in order to work):

           .Db on
           .Op Fl aC Ar file )
           .Db off

     The resulting output:

           DEBUGGING ON
           DEBUG(argv) MACRO: ‘.Op’  Line #: 2
                   Argc: 1  Argv: ‘Fl’  Length: 2
                   Space: ‘’  Class: Executable
                   Argc: 2  Argv: ‘aC’  Length: 2
                   Space: ‘’  Class: Executable
                   Argc: 3  Argv: ‘Ar’  Length: 2
                   Space: ‘’  Class: Executable
                   Argc: 4  Argv: ‘file’  Length: 4
                   Space: ‘ ’  Class: String
                   Argc: 5  Argv: ‘)’  Length: 1
                   Space: ‘ ’  Class: Closing Punctuation or suffix
                   MACRO REQUEST: .Op Fl aC Ar file )
           DEBUGGING OFF

     The first line of information tells the name of the calling macro, here
     ‘.Op’, and the line number it appears on.  If one or more files are
     involved (especially if text from another file is included) the line
     number may be bogus.  If there is only one file, it should be accurate.
     The second line gives the argument count, the argument (‘Fl’) and its
     length.  If the length of an argument is two characters, the argument is
     tested to see if it is executable (unfortunately, any register which
     contains a non-zero value appears executable).  The third line gives the
     space allotted for a class, and the class type.  The problem here is the
     argument aC should not be executable.  The four types of classes are
     string, executable, closing punctuation and opening punctuation.  The
     last line shows the entire argument list as it was read.  In this next
     example, the offending ‘aC’ is escaped:

           .Db on
           .Em An escaped \&aC
           .Db off

           DEBUGGING ON
           DEBUG(fargv) MACRO: ‘.Em’  Line #: 2
                   Argc: 1  Argv: ‘An’  Length: 2
                   Space: ‘ ’  Class: String
                   Argc: 2  Argv: ‘escaped’  Length: 7
                   Space: ‘ ’  Class: String
                   Argc: 3  Argv: ‘aC’  Length: 2
                   Space: ‘ ’  Class: String
                   MACRO REQUEST: .Em An escaped &aC
           DEBUGGING OFF

     The argument ‘\&aC’ shows up with the same length of 2 as the ‘\&’
     sequence produces a zero width, but a register named ‘\&aC’ was not found
     and the type classified as string.

     Other diagnostics consist of usage statements and are self explanatory.

GROFF, TROFF AND NROFF

     The -mdoc package does not need compatibility mode with groff.

     The package inhibits page breaks, and the headers and footers which
     normally occur at those breaks with nroff, to make the manual more
     efficient for viewing on-line.  At the moment, groff with -Tascii does
     eject the imaginary remainder of the page at end of file.  The inhibiting
     of the page breaks makes nroff’d files unsuitable for hardcopy.  There is
     a register named ‘cR’ which can be set to zero in the site dependent
     style file /usr/src/share/tmac/doc-nroff to restore the old style
     behavior.

FILES

     /usr/share/tmac/tmac.doc      manual macro package
     /usr/share/misc/mdoc.template
                                   template for writing a man page
     /usr/share/examples/mdoc/*    several example man pages

SEE ALSO

     man(1), troff(1), mdoc(7)

BUGS

     Undesirable hyphenation on the dash of a flag argument is not yet
     resolved, and causes occasional mishaps in the DESCRIPTION section.
     (line break on the hyphen).

     Predefined strings are not declared in documentation.

     Section 3f has not been added to the header routines.

     ‘.Nm’ font should be changed in NAME section.

     ‘.Fn’ needs to have a check to prevent splitting up if the line length is
     too short.  Occasionally it separates the last parenthesis, and sometimes
     looks ridiculous if a line is in fill mode.

     The method used to prevent header and footer page breaks (other than the
     initial header and footer) when using nroff occasionally places an
     unsightly partially filled line (blank) at the would be bottom of the
     page.

     The list and display macros to not do any keeps and certainly should be
     able to.