Recipe 1.2. Understanding man Pages
1.2.1 Problem
You're
trying to use some programs (for example, everyone's
favorite, grep; the name tells you so much) and
you can't make them them do what you want. So,
heeding the standard "RTFM" (read
the fine man page) advice, you dig up the relevant man pages. But
they don't make a lot of sense—now what?
1.2.2 Solution
Learn how man pages are organized, and familiarize yourself with
their conventions for teaching command syntax and options, and
you'll find that man pages really are helpful.
1.2.3 Discussion
Linux sees all the man pages on a system as part of a single manual.
This manual is divided into sections:
- 1 Executable programs or shell commands
- 2 System calls
- 3 Library calls
- 4 Special files (usually found in /dev)
- 5 File formats and conventions
- 6 Games
- 7 Miscellaneous
- 8 System administration commands
- 9 Nonstandard kernel routines
- n New documentation, which may be moved later
- l Local documentation, specific to your system
Each individual program, utility, or function has its own page in
this manual, like a page in a book. Finding the man page for a
program or command is usually as easy as typing man
foo, where foo is the name of the
program.
You've probably seen references to numbered man
pages, like grep(1). This is referring to
man grep in section 1. Call it up this way:
$ man 1 grep
Some man pages are in more than one section. man
foo will only display the first one. You can
list all of them with the -f switch:
$ man -f man
man (1) an interface to the online reference manuals
man (7) macros to format man pages
Each man page is divided into sections. The section names vary, but
you'll usually see these: NAME, SYNOPSIS,
DESCRIPTION, OPTIONS, FILES, EXAMPLES, SEE ALSO, BUGS, and AUTHOR.
Here's the notation
used to show command syntax, found in the Synopsis of the man pages:
command-name [optional flags] any-other-required-elements
Command flags are shown this way:
- bold text
-
Type this exactly as it is shown.
- italic text
-
Italic text indicates an argument, which means you replace it with
your desired value. Depending on the viewer you are using, you may
not see italics, but rather underlines or bold text.
- [-abc]
-
Everything inside square brackets is optional and can be combined.
- [-a|-b|-c]
-
Options separated by the pipe | (Shift-backslash) cannot be combined.
- argument...
-
The ellipsis indicates that several arguments can be listed. Watch
out for delimiters—usually they are spaces, but sometimes
commas are used.
- [expression] ...
-
The ellipsis indicates that several expressions can be listed.
Short options can be typed two ways:
-abc
or:
-a -b -c
Long options must be individually hyphenated,
and they use double hyphens:
--option1 --option2 --option3
Long options are especially useful in scripts, so you can remember
what the script does.
The bulk of most man pages is a list of the options available.
1.2.4 See Also
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