Chapter 10. Manual Pages

10.1. Introduction

Manual pages, commonly shortened to man pages, were conceived as readily-available reminders for command syntax, device driver details, or configuration file formats. They have become an extremely valuable quick-reference from the command line for users, system administrators, and programmers.

Although intended as reference material rather than tutorials, the EXAMPLES sections of manual pages often provide detailed use case.

Manual pages are generally shown interactively by the man(1) command. When the user types man ls, a search is performed for a manual page matching ls. The first matching result is displayed.

10.2. Sections

Manual pages are grouped into sections. Each section contains manual pages for a specific category of documentation:

Section NumberCategory

1

General Commands

2

System Calls

3

Library Functions

4

Kernel Interfaces

5

File Formats

6

Games

7

Miscellaneous

8

System Manager

9

Kernel Developer

10.3. Markup

Various markup forms and rendering programs have been used for manual pages. FreeBSD has used groff(7) and the newer mandoc(1). Most existing FreeBSD manual pages, and all new ones, use the mdoc(7) form of markup. This is a simple line-based markup that is reasonably expressive. It is mostly semantic: parts of text are marked up for what they are, rather than for how they should appear when rendered. There is some appearance-based markup which is usually best avoided.

Manual page source is usually interpreted and displayed to the screen interactively. The source files can be ordinary text files or compressed with gzip(1) to save space.

Manual pages can also be rendered to other formats, including PostScript for printing or PDF generation. See man(1).

10.3.1. Manual Page Sections

Manual pages are composed of several standard sections. Each section has a title in upper case, and the sections for a particular type of manual page appear in a specific order. For a category 1 General Command manual page, the sections are:

Section NameDescription

NAME

Name of the command

SYNOPSIS

Format of options and arguments

DESCRIPTION

Description of purpose and usage

ENVIRONMENT

Environment settings that affect operation

EXIT STATUS

Error codes returned on exit

EXAMPLES

Examples of usage

COMPATIBILITY

Compatibility with other implementations

SEE ALSO

Cross-reference to related manual pages

STANDARDS

Compatibility with standards like POSIX

HISTORY

History of implementation

BUGS

Known bugs

AUTHORS

People who created the command or wrote the manual page.

Some sections are optional, and the combination of sections for a specific type of manual page vary. Examples of the most common types are shown later in this chapter.

10.3.2. Macros

mdoc(7) markup is based on macros. Lines that begin with a dot contain macro commands, each two or three letters long. For example, consider this portion of the ls(1) manual page:

.Dd December 1, 2015
.Dt LS 1
.Sh NAME
.Nm ls
.Nd list directory contents
.Sh SYNOPSIS
.Nm
.Op Fl -libxo
.Op Fl ABCFGHILPRSTUWZabcdfghiklmnopqrstuwxy1,
.Op Fl D Ar format
.Op Ar
.Sh DESCRIPTION
For each operand that names a
.Ar file
of a type other than
directory,
.Nm
displays its name as well as any requested,
associated information.
For each operand that names a
.Ar file
of type directory,
.Nm
displays the names of files contained
within that directory, as well as any requested, associated
information.

A Document date and Document title are defined. A Section header for the NAME section is defined. Then the Name of the command and a one-line Name description are defined. The SYNOPSIS section begins. This section describes the command-line options and arguments accepted. Name (.Nm) has already been defined, and repeating it here just displays the defined value in the text. An Optional Flag called -libxo is shown. The Fl macro adds a dash to the beginning of flags, so this appears in the manual page as --libxo. A long list of optional single-character flags are shown. An optional -D flag is defined. If the -D flag is given, it must be followed by an Argument. The argument is a format, a string that tells ls(1) what to display and how to display it. Details on the format string are given later in the manual page. A final optional argument is defined. Since no name is specified for the argument, the default of file …​ is used. The Section header for the DESCRIPTION section is defined.

When rendered with the command man ls, the result displayed on the screen looks like this:

LS(1)                   FreeBSD General Commands Manual                  LS(1)

NAME
     ls - list directory contents

SYNOPSIS
     ls [--libxo] [-ABCFGHILPRSTUWZabcdfghiklmnopqrstuwxy1,] [-D format]
        [file ...]

DESCRIPTION
     For each operand that names a file of a type other than directory, ls
     displays its name as well as any requested, associated information.  For
     each operand that names a file of type directory, ls displays the names
     of files contained within that directory, as well as any requested,
     associated information.

Optional values are shown inside square brackets.

10.3.3. Markup Guidelines

The mdoc(7) markup language is not very strict. For clarity and consistency, the FreeBSD Documentation project adds some additional style guidelines:

Only the first letter of macros is upper case

Always use upper case for the first letter of a macro and lower case for the remaining letters.

Begin new sentences on new lines

Start a new sentence on a new line, do not begin it on the same line as an existing sentence.

Update .Dd when making non-trivial changes to a manual page

The Document date informs the reader about the last time the manual page was updated. It is important to update whenever non-trivial changes are made to the manual pages. Trivial changes like spelling or punctuation fixes that do not affect usage can be made without updating .Dd.

Give examples

Show the reader examples when possible. Even trivial examples are valuable, because what is trivial to the writer is not necessarily trivial to the reader. Three examples are a good goal. A trivial example shows the minimal requirements, a serious example shows actual use, and an in-depth example demonstrates unusual or non-obvious functionality.

Include the BSD license

Include the BSD license on new manual pages. The preferred license is available from the Committer’s Guide.

10.3.4. Markup Tricks

Add a space before punctuation on a line with macros. Example:

.Sh SEE ALSO
.Xr geom 4 ,
.Xr boot0cfg 8 ,
.Xr geom 8 ,
.Xr gptboot 8

Note how the commas at the end of the .Xr lines have been placed after a space. The .Xr macro expects two parameters to follow it, the name of an external manual page, and a section number. The space separates the punctuation from the section number. Without the space, the external links would incorrectly point to section 4, or 8,.

10.3.5. Important Macros

Some very common macros will be shown here. For more usage examples, see mdoc(7), groff_mdoc(7), or search for actual use in /usr/share/man/man* directories. For example, to search for examples of the .Bd Begin display macro:

% find /usr/share/man/man* | xargs zgrep '.Bd'

10.3.5.1. Organizational Macros

Some macros are used to define logical blocks of a manual page.

Organizational MacroUse

.Sh

Section header. Followed by the name of the section, traditionally all upper case. Think of these as chapter titles.

.Ss

Subsection header. Followed by the name of the subsection. Used to divide a .Sh section into subsections.

.Bl

Begin list. Start a list of items.

.El

End a list.

.Bd

Begin display. Begin a special area of text, like an indented area.

.Ed

End display.

10.3.5.2. Inline Macros

Many macros are used to mark up inline text.

Inline MacroUse

.Nm

Name. Called with a name as a parameter on the first use, then used later without the parameter to display the name that has already been defined.

.Pa

Path to a file. Used to mark up filenames and directory paths.

10.4. Sample Manual Page Structures

This section shows minimal desired man page contents for several common categories of manual pages.

10.4.1. Section 1 or 8 Command

The preferred basic structure for a section 1 or 8 command:

.Dd August 25, 2017
.Dt EXAMPLECMD 8
.Os
.Sh NAME
.Nm examplecmd
.Nd "command to demonstrate section 1 and 8 man pages"
.Sh SYNOPSIS
.Nm
.Op Fl v
.Sh DESCRIPTION
The
.Nm
utility does nothing except demonstrate a trivial but complete
manual page for a section 1 or 8 command.
.Sh SEE ALSO
.Xr exampleconf 5
.Sh AUTHORS
.An Firstname Lastname Aq Mt flastname@example.com

10.4.2. Section 4 Device Driver

The preferred basic structure for a section 4 device driver:

.Dd August 25, 2017
.Dt EXAMPLEDRIVER 4
.Os
.Sh NAME
.Nm exampledriver
.Nd "driver to demonstrate section 4 man pages"
.Sh SYNOPSIS
To compile this driver into the kernel, add this line to the
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device exampledriver"
.Ed
.Pp
To load the driver as a module at boot, add this line to
.Xr loader.conf 5 :
.Bd -literal -offset indent
exampledriver_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides an opportunity to show a skeleton or template
file for section 4 manual pages.
.Sh HARDWARE
The
.Nm
driver supports these cards from the aptly-named Nonexistent
Technologies:
.Pp
.Bl -bullet -compact
.It
NT X149.2 (single and dual port)
.It
NT X149.8 (single port)
.El
.Sh DIAGNOSTICS
.Bl -diag
.It "flashing green light"
Something bad happened.
.It "flashing red light"
Something really bad happened.
.It "solid black light"
Power cord is unplugged.
.El
.Sh SEE ALSO
.Xr example 8
.Sh HISTORY
The
.Nm
device driver first appeared in
.Fx 49.2 .
.Sh AUTHORS
.An Firstname Lastname Aq Mt flastname@example.com

10.4.3. Section 5 Configuration File

The preferred basic structure for a section 5 configuration file:

.Dd August 25, 2017
.Dt EXAMPLECONF 5
.Os
.Sh NAME
.Nm example.conf
.Nd "config file to demonstrate section 5 man pages"
.Sh DESCRIPTION
.Nm
is an example configuration file.
.Sh SEE ALSO
.Xr example 8
.Sh AUTHORS
.An Firstname Lastname Aq Mt flastname@example.com

10.5. Testing

Testing a new manual page can be challenging. Fortunately there are some tools that can assist in the task. Some of them, like man(1), do not look in the current directory. It is a good idea to prefix the filename with ./ if the new manual page is in the current directory. An absolute path can also be used.

Use mandoc(1)'s linter to check for parsing errors:

% mandoc -T lint ./mynewmanpage.8

Use textproc/igor to proofread the manual page:

% igor ./mynewmanpage.8

Use man(1) to check the final result of your changes:

% man ./mynewmanpage.8

You can use col(1) to filter the output of man(1) and get rid of the backspace characters before loading the result in your favorite editor for spell checking:

% man ./mynewmanpage.8 | col -b | vim -R -

Spell-checking with fully-featured dictionaries is encouraged, and can be accomplished by using textproc/hunspell or textproc/aspell combined with textproc/en-hunspell or textproc/en-aspell, respectively. For instance:

% aspell check --lang=en --mode=nroff ./mynewmanpage.8

10.6. Example Manual Pages to Use as Templates

Some manual pages are suitable as in-depth examples.

Manual PagePath to Source Location

cp(1)

/usr/src/bin/cp/cp.1

vt(4)

/usr/src/share/man/man4/vt.4

crontab(5)

/usr/src/usr.sbin/cron/crontab/crontab.5

gpart(8)

/usr/src/sbin/geom/class/part/gpart.8


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