Macro Usage

In general, GNU troff(1) macros accept an unlimited number of arguments (contrary to other versions of troff which can't handle more than nine arguments). In limited cases, arguments may be continued or extended on the next line (See Extended Arguments below). Almost all 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 which is defined 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). This makes it possible to nest macros; for example the option macro, ‘.Op’, may call the flag and argument macros, ‘Fl’ and ‘Ar’, to specify an optional flag with an argument:

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

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. 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.

In the following, we call an -mdoc macro which starts a line (with a leading dot) a command if this distinction is necessary.

Passing Space Characters in an Argument

There are two possible ways to pass an argument which contains an embedded space. 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. This method is useful for strings which are not expected to overlap a line boundary. An alternative is to use ‘\~’, a paddable (i.e. stretchable), unbreakable space (this is a GNU troff(1) extension). The second method is to enclose the string with double quotes.

For example:

If the ‘\’ before the space in the first example or double quotes in the second example were omitted, ‘.Fn’ would see three arguments, and the result would be:

Trailing Blank Space Characters

Escaping Special Characters

Other Possible Pitfalls

Leading spaces will cause a break and are output directly. Avoid this behaviour if possible. Similarly, do not use more than one space character between words in an ordinary text line; contrary to other text formatters, they are not replaced with a single space.

You can't pass ‘"’ directly as an argument. Use ‘\*[q]’ (or ‘\*q’) instead.

By default, troff(1) inserts two space characters after a punctuation mark closing a sentence; characters like ‘)’ or ‘'’ are treated transparently, not influencing the sentence-ending behaviour. To change this, insert ‘\&’ before or after the dot:

The
.Ql .
character.
.Pp
The
.Ql \&.
character.
.Pp
.No test .
test
.Pp
.No test.
test

gives

As can be seen in the first and third line, -mdoc handles punctuation characters specially in macro arguments. This will be explained in section General Syntax below. In the same way, you have to protect trailing full stops of abbreviations with a trailing zero-width space: ‘e.g.\&’.

A comment in the source file of a man page can be either started with ‘.\"’ on a single line, ‘\"’ after some input, or ‘\#’ anywhere (the latter is a GNU troff(1) extension); the rest of such a line is ignored.

What's in a Name...

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

‘.Xx’ is a macro command, and anything following it are arguments 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:

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 meta arguments; in this example, the user has to replace the meta expressions given in angle brackets with real file names. Note that in this document meta arguments are used to describe -mdoc commands; in most man pages, meta variables are not specifically written with angle brackets. The macros which formatted the above example:

.Nm filter
.Op Fl flag
.Ao Ar infile Ac Ao Ar outfile Ac

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:

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 Ns = Ns Ar value
.Bk
.Op Ar target ...
.Ek

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

General Syntax

The result is:

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

The result is:

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

Addresses

The default width is 12n.

Author Name

The default width is 12n.

In the AUTHORS section, the ‘.An’ command causes a line break allowing each new name to appear on its own line. If this is not desirable,

.An -nosplit

call will turn this off. To turn splitting back on, write

.An -split

Arguments

The default width is 12n.

Configuration Declaration (Section Four Only)

In the SYNOPSIS section a ‘.Cd’ command causes a line break before and after its arguments are printed.

The default width is 12n.

Command Modifiers

The default width is 10n.

Defined Variables

The default width is 12n.

Errno's

The default width is 17n.

Environment Variables

The default width is 15n.

Flags

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 default width is 12n.

Function Declarations

In the SYNOPSIS section a ‘.Fd’ command 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.

The ‘.In’ macro, while in the SYNOPSIS section, represents the #include statement, and is the short form of the above example. It specifies the C header file as being included in a C program. It also causes a line break.

While not in the SYNOPSIS section, it represents the header file enclosed in angle brackets.

Function Types

Functions (Library Routines)

Note that any call to another macro signals the end of the ‘.Fn’ call (it will insert a closing parenthesis at that point).

For functions with many parameters (which is rare), the macros ‘.Fo’ (function open) and ‘.Fc’ (function close) may be used with ‘.Fa’ (function argument).

Example:

.Ft int
.Fo 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:

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.

The default width values of ‘.Fn’ and ‘.Fo’ are 12n and 16n, respectively.

Function Arguments

The default width is 12n.

Return Values

For example, ‘.Rv -std atexit’ produces:

The -std option is valid only for manual page sections 2 and 3. Currently, this macro does nothing if used without the -std flag.

Exit Status

For example, ‘.Ex -std cat’ produces:

The -std option is valid only for manual page sections 1, 6 and 8. Currently, this macro does nothing if used without the -std flag.

Interactive Commands

The default width is 12n.

Library Names

Available arguments to ‘.Lb’ and their results are:

Local, OS-specific additions might be found in the file mdoc.local; look for strings named ‘str-Lb-XXX’. ‘XXX’ then denotes the keyword to be used with the ‘.Lb’ macro.

Literals

The default width is 16n.

Names

The default width is 10n.

Options

Here a typical example of the ‘.Oo’ and ‘.Oc’ macros:

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

Produces:

The default width values of ‘.Op’ and ‘.Oo’ are 14n and 10n, respectively.

Pathnames

The default width is 32n.

Standards

Available pairs for “Abbreviation/Formal Name” are:

ANSI/ISO C

POSIX Part 1: System API

POSIX Part 2: Shell and Utilities

X/Open

Miscellaneous

Variable Types

Variables

The default width is 12n.

Manual Page Cross References

The default width is 10n.

AT&T Macro

The following values for ⟨version⟩ are possible:

BSD Macro

⟨version⟩ will be prepended to the string ‘BSD’. The following values for ⟨release⟩ are possible:

NetBSD Macro

For possible values of ⟨version⟩ see the description of the ‘.Os’ command above in section TITLE MACROS.

FreeBSD Macro

For possible values of ⟨version⟩ see the description of the ‘.Os’ command above in section TITLE MACROS.

OpenBSD Macro

BSD/OS Macro

UNIX Macro

Emphasis Macro

The default width is 10n.

Font Mode

‘.Bf’ has the following syntax:

⟨font mode⟩ must be one of the following three types:

Both macros are neither callable nor parsed.

Enclosure and Quoting Macros

All macros ending with ‘q’ and ‘o’ have a default width value of 12n.

.Eo, .Ec

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

.Es, .En

Due to the nine-argument limit in the original troff program two other macros have been implemented which are now rather obsolete: ‘.Es’ takes the first and second parameter as the left and right enclosure string, which are then used to enclose the arguments of ‘.En’. The default width value is 12n for both macros.

.Eq

The first and second arguments of this macro are the opening and closing strings respectively, followed by the arguments to be enclosed.

.Ql

The quoted literal macro behaves differently in troff and nroff mode. 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.

The default width is 16n.

.Pf

The prefix macro suppresses the whitespace between its first and second argument:

.Pf ( Fa name2

(name2

The default width is 12n.

The ‘.Ns’ macro (see below) performs the analogous suffix function.

.Ap

The ‘.Ap’ macro inserts an apostrophe and exits any special text modes, continuing in ‘.No’ mode.

Examples of quoting:

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 are discussed below.

No-Op or Normal Text Macro

The default width is 12n.

No-Space Macro

Note: The ‘.Ns’ macro always invokes the ‘.No’ macro after eliminating the space unless another macro name follows it. If used as a command (i.e., the second form above in the ‘Usage’ line), ‘.Ns’ is identical to ‘.No’.

Section Cross References

The default width is 16n.

Symbolics

The default width is 6n.

Mathematical Symbols

The default width is 6n.

References and Citations

Macros beginning with ‘%’ are not callable but accept multiple arguments in the usual way. Only the ‘.Tn’ macro is handled properly as a parameter; other macros will cause strange output. ‘.%B’ and ‘.%T’ can be used outside of the ‘.Rs/.Re’ environment.

Example:

.Rs
.%A "Matthew Bar"
.%A "John Foo"
.%T "Implementation Notes on foobar(1)"
.%R "Technical Report ABC-DE-12-345"
.%Q "Drofnats College, Nowhere"
.%D "April 1991"
.Re

produces

Trade Names (or Acronyms and Type Names)

The default width is 10n.

Extended Arguments

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

Another one:

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

produces

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

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

produces

Section Headers

The default width is 8n.

.Sh NAME

The ‘.Sh NAME’ macro is mandatory. If not specified, 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.

‘.Nd’ first prints ‘-’, then all its arguments.

.Sh LIBRARY

This section is for section two and three function calls. It should consist of a single ‘.Lb’ macro call; see Library Names.

.Sh SYNOPSIS

The SYNOPSIS section describes the typical usage of the subject of a man page. The macros required are either ‘.Nm’, ‘.Cd’, or ‘.Fn’ (and possibly ‘.Fo’, ‘.Fc’, ‘.Fd’, and ‘.Ft’). 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, and 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

.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).

.Sh IMPLEMENTATION NOTES

Implementation specific information should be placed here.

.Sh RETURN VALUES

Sections 2, 3 and 9 function return values should go here. The ‘.Rv’ macro may be used to generate text for use in the RETURN VALUES section for most section 2 and 3 library functions; see Return Values.

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 FILES

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

.Sh EXAMPLES

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

.Sh DIAGNOSTICS

Diagnostic messages from a command should be placed in this section. The ‘.Ex’ macro may be used to generate text for use in the DIAGNOSTICS section for most section 1, 6 and 8 commands; see Exit Status.

.Sh COMPATIBILITY

Known compatibility issues (e.g. deprecated options or parameters) should be listed here.

.Sh ERRORS

Specific error handling, especially from library functions (man page sections 2, 3, and 9) should go here. The ‘.Er’ macro is used to specify an error (errno).

.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. Currently refer(1) style references are not accommodated.

It is recommended that the cross references are sorted on the section number, then alphabetically on the names within a section, and placed in that order and comma separated. Example:

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

.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 C89”) 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 should be placed here. The ‘.An’ macro should be used to specify the name(s) of the person(s).

.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"

Subsection Headers

The default width is 8n.

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’ or ‘.Bd’ macro (which both assert a vertical distance unless the -compact flag is given).

The macro is neither callable nor parsed and takes no arguments; an alternative name is ‘.Lp’.

Keeps

Both macros are neither callable nor parsed.

More work needs to be done with the keep macros; specifically, a -line option should be added.

Examples and Displays

.D1

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

-ldghfstru

The above was produced by: .D1 Fl ldghfstru.

.Dl

(This is D-ell.) Display one line of indented literal text. The ‘.Dl’ example macro has been used throughout this file. It allows the indentation (display) of one line of text. Its default font is set to constant width (literal). ‘.Dl’ is parsed but not callable.

% 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. It has the following syntax:

.Bd {-literal | -filled | -unfilled | -ragged | -centered} [-offset ⟨string⟩] [-file ⟨file name⟩] [-compact]

 

-ragged

Fill, but do not adjust the right margin (only left-justify).

-centered

Center lines between the current left and right margin. Note that each single line is centered.

-unfilled

Do not fill; display a block of text as typed, using line breaks as specified by the user. This can produce overlong lines without warning messages.

-filled

Display a filled block. The block of text is formatted (i.e., the text is justified on both the left and right side).

-literal

Display block with literal font (usually fixed-width). Useful for source code or simple tabbed or spaced text.

-file ⟨file name⟩

The file whose name follows the -file flag is read and displayed before any data enclosed with ‘.Bd’ and ‘.Ed’, using the selected display type. Any troff/-mdoc commands in the 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

Indent by one default indent value or tab. The default indent value is also used for the ‘.D1’ and ‘.Dl’ macros, so one is guaranteed the two types of displays will line up. The indentation value is normally set to 6n or about two thirds of an inch (six constant width characters).

indent-two

Indent 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 within troff.

If ⟨string⟩ is a valid numeric expression instead (with a scale indicator other than ‘u’), use that value for indentation. The most useful scale indicators are ‘m’ and ‘n’, specifying the so-called Em and En square. This is approximately the width of the letters ‘m’ and ‘n’ respectively of the current font (for nroff output, both scale indicators give the same values). If ⟨string⟩ isn't a numeric expression, it is tested whether it is an -mdoc macro name, and the default offset value associated with this macro is used. Finally, if all tests fail, the width of ⟨string⟩ (typeset with a fixed-width font) is taken as the offset.

-compact

Suppress insertion of vertical space before begin of display.

.Ed

End display (takes no arguments).

Lists and 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).

It has the following syntax forms:

And now a detailed description of the list types.

-bullet

A bullet list.

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

Produces:

• Bullet one goes here.
• Bullet two here.

-dash (or -hyphen)

A dash list.

.Bl -dash -offset indent -compact
.It
Dash one goes here.
.It
Dash two here.
.El
    

Produces:

• Dash one goes here.
• Dash two here.

-enum

An enumerated list.

.Bl -enum -offset indent -compact
.It
Item one goes here.
.It
And item two here.
.El
    

The result:

1. Item one goes here.
2. And item two here.

If you want to nest enumerated lists, use the -nested flag (starting with the second-level list):

.Bl -enum -offset indent -compact
.It
Item one goes here
.Bl -enum -nested -compact
.It
Item two goes here.
.It
And item three here.
.El
.It
And item four here.
.El
    

Result:

1. Item one goes here.
   1. Item two goes here.
   2. And item three here.
2. And item four here.

-item

A list of type -item without list markers.

.Bl -item -offset indent
.It
Item one goes here.
Item one goes here.
Item one goes here.
.It
Item two here.
Item two here.
Item two here.
.El
    

Produces:

• Item one goes here. Item one goes here. Item one goes here.
• Item two here. Item two here. Item two here.

-tag

A list with tags. Use -width to specify the tag width.

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 priority (non-positive when in non-interruptible wait)

The raw text:

.Bl -tag -width "PPID" -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 priority
(non-positive when in non-interruptible wait)
.El
    

-diag

Diag lists create section four diagnostic lists and are similar to inset lists except callable macros are ignored. The -width flag is not meaningful in this context.

Example:

.Bl -diag
.It You can't use Sy here.
The message says all.
.El
    

produces

You can't use Sy here.

The message says all.

-hang

A list with hanging tags.

Hanged

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

Longer hanged list labels

blend into 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 into the paragraph unlike
tagged paragraph labels.
.El
    

-ohang

Lists with overhanging tags do not use indentation for the items; tags are written to a separate line.

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 priority (non-positive when in non-interruptible wait)

The raw text:

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

-inset

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. Use a -width attribute as described below.

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
    

-column

This list type generates multiple columns. The number of columns and the width of each column is determined by the arguments to the -column list, ⟨string1⟩, ⟨string2⟩, etc. If ⟨stringN⟩ starts with a ‘.’ (dot) immediately followed by a valid -mdoc macro name, interpret ⟨stringN⟩ and use the width of the result. Otherwise, the width of ⟨stringN⟩ (typeset with a fixed-width font) is taken as the Nth column width.

Each ‘.It’ argument is parsed to make a row, each column within the row is a separate argument separated by a tab or the ‘.Ta’ macro.

The table:

String	Nroff	Troff
<=	<=	≤
>=	>=	≥

was produced by:

.Bl -column -offset indent ".Sy String" ".Sy Nroff" ".Sy Troff"
.It Sy String Ta Sy Nroff Ta Sy Troff
.It Li <= Ta <= Ta \*(<=
.It Li >= Ta >= Ta \*(>=
.El
    

Other keywords:

-width ⟨string⟩

If ⟨string⟩ starts with a ‘.’ (dot) immediately followed by a valid -mdoc macro name, interpret ⟨string⟩ and use the width of the result. Almost all lists in this document use this option.

Example:

.Bl -tag -width ".Fl test Ao Ar string Ac"
.It Fl test Ao Ar string Ac
This is a longer sentence to show how the
.Fl width
flag works in combination with a tag list.
.El
    

gives:

-test ⟨string⟩

This is a longer sentence to show how the -width flag works in combination with a tag list.

(Note that the current state of -mdoc is saved before ⟨string⟩ is interpreted; afterwards, all variables are restored again. However, boxes (used for enclosures) can't be saved in GNU troff(1); as a consequence, arguments must always be balanced to avoid nasty errors. For example, do not write ‘.Ao Ar string’ but ‘.Ao Ar string Xc’ instead if you really need only an opening angle bracket.)

Otherwise, if ⟨string⟩ is a valid numeric expression (with a scale indicator other than ‘u’), use that value for indentation. The most useful scale indicators are ‘m’ and ‘n’, specifying the so-called Em and En square. This is approximately the width of the letters ‘m’ and ‘n’ respectively of the current font (for nroff output, both scale indicators give the same values). If ⟨string⟩ isn't a numeric expression, it is tested whether it is an -mdoc macro name, and the default width value associated with this macro is used. Finally, if all tests fail, the width of ⟨string⟩ (typeset with a fixed-width font) is taken as the width.

If a width is not specified for the tag list type, every 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; otherwise, the default width of ‘.No’ is used.

-offset ⟨string⟩

If ⟨string⟩ is indent, a default indent value (normally set to 6n, similar to the value used in ‘.Dl’ or ‘.Bd’) is used. If ⟨string⟩ is a valid numeric expression instead (with a scale indicator other than ‘u’), use that value for indentation. The most useful scale indicators are ‘m’ and ‘n’, specifying the so-called Em and En square. This is approximately the width of the letters ‘m’ and ‘n’ respectively of the current font (for nroff output, both scale indicators give the same values). If ⟨string⟩ isn't a numeric expression, it is tested whether it is an -mdoc macro name, and the default offset value associated with this macro is used. Finally, if all tests fail, the width of ⟨string⟩ (typeset with a fixed-width font) is taken as the offset.

-compact

Suppress insertion of vertical space before the list and between list items.