LinuxGuide.it > Linux Man Page: "man"

The Linux Documentation Project maintains an archive of snaphots of the (English language) core Linux manual pages that are maintained by Michael Kerrisk. Corrections and additions are welcome, but review the "Help Wanted" list, first.

Man pages belonging to programs are usually distributed together with those programs. Therefore, the core Linux man-pages mainly contains the pages for system calls and library routines, special devices, and file formats. However, it also contains documentation for a few programs, in cases where the authors or maintainers of the program do not distribute man pages themselves.

This page is part of release 3.11 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages

man page(1) manual page Table of Contents

Name

man - format and display the on-line manual pages

Synopsis

man [-acdfFhkKtwW] [--path] [-m system] [-p string] [-C config_file] [-M pathlist] [-P pager] [-B browser] [-H htmlpager] [-S section_list] [section] name ...

Description

man formats and displays the on-line manual pages. If you specify sec_tion, man only looks in that section of the manual. name is normally the name of the manual page, which is typically the name of a command, function, or file. However, if name contains a slash (/) then man interprets it as a file specification, so that you can do man ./foo.5 or even man /cd/foo/bar.1.gz.

See below for a description of where man looks for the manual page files.

Options

-C config_file
Specify the configuration file to use; the default is /etc/man.config. (See man.config(5) .)

-M: path Specify the list of directories to search for man pages. Separate the directories with colons. An empty list is the same as not specifying -M at all. See SEARCH PATH FOR MANUAL PAGES.
-P: pager Specify which pager to use. This option overrides the MANPAGER environment variable, which in turn overrides the PAGER variable. By default, man uses /usr/bin/less -is.
-B: Specify which browser to use on HTML files. This option overrides the BROWSER environment variable. By default, man uses /usr/bin/less-is,
-H: Specify a command that renders HTML files as text. This option overrides the HTMLPAGER environment variable. By default, man uses /bin/cat,
-S: section_list List is a colon separated list of manual sections to search. This option overrides the MANSECT environment variable.
-a: By default, man will exit after displaying the first manual page it finds. Using this option forces man to display all the manual pages that match name, not just the first.
-c: Reformat the source man page, even when an up-to-date cat page exists. This can be meaningful if the cat page was formatted for a screen with a different number of columns, or if the preformatted page is corrupted.
-d: Don’t actually display the man pages, but do print gobs of debugging information.
-D: Both display and print debugging info.
-f: Equivalent to whatis.
-F or --preformat: Format only - do not display.
-h: Print a help message and exit.
-k: Equivalent to apropos.
-K: Search for the specified string in *all* man pages. Warning: this is probably very slow! It helps to specify a section. (Just to give a rough idea, on my machine this takes about a minute per 500 man pages.)
-m: system Specify an alternate set of man pages to search based on the system name given.
-p: string Specify the sequence of preprocessors to run before nroff or troff. Not all installations will have a full set of preprocessors. Some of the preprocessors and the letters used to designate them are: eqn (e), grap (g), pic (p), tbl (t), vgrind (v), refer (r). This option overrides the MANROFFSEQ environment variable.
-t: Use /usr/bin/groff -Tps -mandoc to format the manual page, passing the output to stdout. The default output format of /usr/bin/groff -Tps -mandoc is Postscript, refer to the manual page of /usr/bin/groff -Tps -mandoc for ways to pick an alternate format.

Depending on the selected format and the availability of printing devices, the output may need to be passed through some filter or another before being printed.

-w or --path: Don’t actually display the man pages, but do print the location(s) of the files that would be formatted or displayed. If no argument is given: display (on stdout) the list of directories that is searched by man for man pages. If manpath is a link to man, then “manpath” is equivalent to “man --path".
-W: Like -w, but print file names one per line, without additional information. This is useful in shell commands like man -aW man | xargs ls -l

Cat Pages

Man will try to save the formatted man pages, in order to save formatting time the next time these pages are needed. Traditionally, formatted versions of pages in DIR/manX are saved in DIR/catX, but other mappings from man dir to cat dir can be specified in /etc/man.config. No cat pages are saved when the required cat directory does not exist. No cat pages are saved when they are formatted for a line length different from 80. No cat pages are saved when man.config contains the line NOCACHE.

It is possible to make man suid to a user man. Then, if a cat directory has owner man and mode 0755 (only writable by man), and the cat files have owner man and mode 0644 or 0444 (only writable by man, or not writable at all), no ordinary user can change the cat pages or put other files in the cat directory. If man is not made suid, then a cat directory should have mode 0777 if all users should be able to leave cat pages there.

The option -c forces reformatting a page, even if a recent cat page exists.

HTML Pages

Man will find HTML pages if they live in directories named as expected to be “.html", thus a valid name for an HTML version of the ls(1) man page would be /usr/share/man/htmlman1/ls.1.html.

Search Path for Manual Pages

man uses a sophisticated method of finding manual page files, based on the invocation options and environment variables, the /etc/man.config configuration file, and some built in conventions and heuristics.

First of all, when the name argument to man contains a slash (/), man assumes it is a file specification itself, and there is no searching involved.

But in the normal case where name doesn’t contain a slash, man searches a variety of directories for a file that could be a manual page for the topic named.

If you specify the -M pathlist option, pathlist is a colon-separated list of the directories that man searches.

If you don’t specify -M but set the MANPATH environment variable, the value of that variable is the list of the directories that man searches.

If you don’t specify an explicit path list with -M or MANPATH, man develops its own path list based on the contents of the configuration file /etc/man.config. The MANPATH statements in the configuration file identify particular directories to include in the search path.

Furthermore, the MANPATH_MAP statements add to the search path depending on your command search path (i.e. your PATH environment variable). For each directory that may be in the command search path, a MANPATH_MAP statement specifies a directory that should be added to the search path for manual page files. man looks at the PATH variable and adds the corresponding directories to the manual page file search path. Thus, with the proper use of MANPATH_MAP, when you issue the command man xyz, you get a manual page for the program that would run if you issued the command xyz.

In addition, for each directory in the command search path (we’ll call it a “command directory") for which you do not have a MANPATH_MAP statement, man automatically looks for a manual page directory “nearby" namely as a subdirectory in the command directory itself or in the parent directory of the command directory.

You can disable the automatic “nearby” searches by including a NOAUTOPATH statement in /etc/man.config.

In each directory in the search path as described above, man searches for a file named topic.section, with an optional suffix on the section number and possibly a compression suffix. If it doesn’t find such a file, it then looks in any subdirectories named manN or catN where N is the manual section number. If the file is in a catN subdirectory, man assumes it is a formatted manual page file (cat page). Otherwise, man assumes it is unformatted. In either case, if the filename has a known compression suffix (like .gz), man assumes it is gzipped.

If you want to see where (or if) man would find the manual page for a particular topic, use the --path (-w) option.

Environment

MANPATH
If MANPATH is set, man uses it as the path to search for manual page files. It overrides the configuration file and the automatic search path, but is overridden by the -M invocation option. See SEARCH PATH FOR MANUAL PAGES.

MANPL If MANPL is set, its value is used as the display page length. Otherwise, the entire man page will occupy one (long) page.

MANROFFSEQ: If MANROFFSEQ is set, its value is used to determine the set of preprocessors run before running nroff or troff. By default, pages are passed through the tbl preprocessor before nroff.
MANSECT: If MANSECT is set, its value is used to determine which manual sections to search.
MANWIDTH: If MANWIDTH is set, its value is used as the width manpages should be displayed. Otherwise the pages may be displayed over the whole width of your screen.
MANPAGER: If MANPAGER is set, its value is used as the name of the program to use to display the man page. If not, then PAGER is used. If that has no value either, /usr/bin/less -is is used.
BROWSER: The name of a browser to use for displaying HTML manual pages. If it is not set, /usr/bin/less -is is used.
HTMLPAGER: The command to use for rendering HTML manual pages as text. If it is not set, /bin/cat is used.

LANG If LANG is set, its value defines the name of the subdirectory where man first looks for man pages. Thus, the command ‘LANG=dk man 1 foo’ will cause man to look for the foo man page in .../dk/man1/foo.1, and if it cannot find such a file, then in .../man1/foo.1, where ... is a directory on the search path.

NLSPATH, LC_MESSAGES, LANG: The environment variables NLSPATH and LC_MESSAGES (or LANG when the latter does not exist) play a role in locating the message catalog. (But the English messages are compiled in, and for English no catalog is required.) Note that programs like col(1) called by man also use e.g. LC_CTYPE.

PATH PATH helps determine the search path for manual page files. See SEARCH PATH FOR MANUAL PAGES.

SYSTEM SYSTEM is used to get the default alternate system name (for use with the -m option).

Bugs

The -t option only works if a troff-like program is installed. If you see blinking \255 or <AD> instead of hyphens, put ‘LESSCHARSET=latin1’ in your environment.

Tips

If you add the line

(global-set-key [(f1)] (lambda () (interactive) (manual-entry (current-word))))

to your .emacs file, then hitting F1 will give you the man page for the library call at the current cursor position.

To get a plain text version of a man page, without backspaces and underscores, try

# man foo | col -b > foo.mantxt

Author

John W. Eaton was the original author of man. Zeyd M. Ben-Halim released man 1.2, and Andries Brouwer followed up with versions 1.3 thru 1.5p. Federico Lucifredi <flucifredi@acm.org> is the current maintainer.