Difference between revisions of "Man page"

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[[KDE]] users can read man pages in Konqueror using:
 
[[KDE]] users can read man pages in Konqueror using:
 
  man:<name>
 
  man:<name>
From the [[Official Repositories]] come two other possibilities:
+
From the [[Official repositories]] come two other possibilities:
  
 
1. {{pkg|xorg-xman}} provides a categorized look at man pages in [[X]].
 
1. {{pkg|xorg-xman}} provides a categorized look at man pages in [[X]].

Revision as of 11:52, 24 February 2014

man pages (abbreviation for "manual pages") are the extensive documentation that comes preinstalled with almost all substantial UNIX-like operating systems, including Arch Linux. The command used to display them is man.

In spite of their scope, man pages are designed to be self-contained documents, consequentially limiting themselves to referring to other man pages when discussing related subjects. This is in sharp contrast with the hyperlink-aware info files, GNU's attempt at replacing the traditional man page format.

Accessing Man Pages

To read a man page, simply enter:

$ man page_name

Manuals are sorted into several sections:

  1. General commands
  2. System calls (functions provided by the kernel)
  3. Library calls (C library functions)
  4. Special files (usually found in /dev) and drivers
  5. File formats and conventions
  6. Games
  7. Miscellaneous (including conventions)
  8. System administration commands (usually requiring root privileges) and daemons

Man pages are usually referred to by their name, followed by their section number in parentheses. Often there are multiple man pages of the same name, such as man(1) and man(7). In this case, give man the section number followed by the name of the man page, for example:

$ man 5 passwd

to read the man page on /etc/passwd, rather than the passwd utility.

Very brief descriptions of programs can be read out of man pages without displaying the whole page using the whatis command. For example, for a brief description of ls, type:

$ whatis ls

and whatis will output "list directory contents."

Format

Man pages all follow a fairly standard format, which helps in navigating them. Some sections which are often present include:

  • NAME - The name of the command and a one-line statement of its purpose.
  • SYNOPSIS - A list of the options and arguments a command takes or the parameters the function takes and its header file.
  • DESCRIPTION - A more in depth description of a command or function's purpose and workings.
  • EXAMPLES - Common examples, usually ranging from the simple to the relatively complex.
  • OPTIONS - Descriptions of each of the options a command takes and what they do.
  • EXIT STATUS - The meanings of different exit codes.
  • FILES - Files related to a command or function.
  • BUGS - Problems with the command or function that are pending repair. Also known as KNOWN BUGS.
  • SEE ALSO - A list of related commands or functions.
  • AUTHOR, HISTORY, COPYRIGHT, LICENSE, WARRANTY - Information about the program, its past, its terms of use, and its creator.

Searching manuals

Whilst the man utility allows users to display man pages, a problem arises when one knows not the exact name of the desired manual page in the first place! Fortunately, the -k or --apropos options can be used to search the manual page descriptions for instances of a given keyword.

The research feature is provided by a dedicated cache. By default you may not have any cache built and all your searches will give you the nothing appropriate result. You can generate the cache or update it by running

# mandb

You should run it everytime a new manpage is installed.

Now you can begin your search. For example, to search for man pages related to "password":

$ man -k password

or:

$ man --apropos password

This is equivalent to calling the apropos command:

$ apropos password

The given keyword is interpreted as a regular expression by default.

If you want to do a more in-depth search by matching the keywords found in the whole articles, you can use the -K option:

$ man -K password

Colored man pages

Color-enabled man pages allow for a clearer presentation and easier digestion of the content. There are two prevalent methods for achieving colored man pages: using less, or opting for most.

Using less (Recommended)

Source: Less Colors For Man Pages | Linux Tidbits

This method has the advantage that less has a bigger feature set than most, and is the default for viewing man pages.

Add the following to a shell configuration file. For Bash it would be:

~/.bashrc
man() {
    env LESS_TERMCAP_mb=$'\E[01;31m' \
    LESS_TERMCAP_md=$'\E[01;38;5;74m' \
    LESS_TERMCAP_me=$'\E[0m' \
    LESS_TERMCAP_se=$'\E[0m' \
    LESS_TERMCAP_so=$'\E[38;5;246m' \
    LESS_TERMCAP_ue=$'\E[0m' \
    LESS_TERMCAP_us=$'\E[04;38;5;146m' \
    man "$@"
}

To see the changes in your Man Pages (without restarting bash or linux), you may run:

# source ~/.bashrc

To customize the colors, see Wikipedia:ANSI escape code for reference.

Using most (Not recommended)

The basic function of 'most' is similar to less and more, but it has a smaller feature set. Configuring most to use colors is easier than using less, but additional configuration is necessary to make most behave like less. Install most using pacman:

# pacman -S most

Edit /etc/man_db.conf, uncomment the pager definition and change it to:

DEFINE     pager     most -s

Test the new setup by typing:

$ man whatever_man_page

Modifying the color values requires editing ~/.mostrc (creating the file if it is not present) or editing /etc/most.conf for system-wide changes. Example ~/.mostrc:

% Color settings
color normal lightgray black
color status yellow blue
color underline yellow black
color overstrike brightblue black

Another example showing keybindings similar to less (jump to line is set to 'J'):

% less-like keybindings
unsetkey "^K"
unsetkey "g"
unsetkey "G"
unsetkey ":"

setkey next_file ":n"
setkey find_file ":e"
setkey next_file ":p"
setkey toggle_options ":o"
setkey toggle_case ":c"
setkey delete_file ":d"
setkey exit ":q"

setkey bob "g"
setkey eob "G"
setkey down "e"
setkey down "E"
setkey down "j"
setkey down "^N"
setkey up "y"
setkey up "^Y"
setkey up "k"
setkey up "^P"
setkey up "^K"
setkey page_down "f"
setkey page_down "^F"
setkey page_up "b"
setkey page_up "^B"
setkey other_window "z"
setkey other_window "w"
setkey search_backward "?"
setkey bob "p"
setkey goto_mark "'"
setkey find_file "E"
setkey edit "v"

Colored man pages on xterm or rxvt-unicode

Source: XFree resources file for XTerm programTemplate:Linkrot

A quick way to add color to manual pages viewed on xterm/uxterm or rxvt-unicode is to modify ~/.Xresources.

xterm

*VT100.colorBDMode:     true
*VT100.colorBD:         red
*VT100.colorULMode:     true
*VT100.colorUL:         cyan

which replaces the decorations with the colors. Also add:

*VT100.veryBoldColors: 6

if you want colors and decorations (bold or underline) at the same time. See man xterm for a description of the veryBoldColors resource.

rxvt-unicode

URxvt.colorIT:      #87af5f
URxvt.colorBD:      #d7d7d7
URxvt.colorUL:      #87afd7

Run:

$ xrdb -load ~/.Xresources

Launch a new xterm/uxterm or rxvt-unicode and you should see colorful man pages. This combination puts colors to bold and underlined words in xterm/uxterm or to bold, underlined, and italicized text in rxvt-unicode. You can play with different combinations of these attributes (see the sourcesTemplate:Linkrot of this item).

Reading local man pages

Instead of the standard interface, using browsers such as lynx and Firefox to view man pages allows users to reap info pages' main benefit: hyperlinked text.

KDE users can read man pages in Konqueror using:

man:<name>

From the Official repositories come two other possibilities:

1. xorg-xman provides a categorized look at man pages in X.

2. The GNOME Help Browser yelp is a more neat way but has some dependencies.

Converting to browser-readable HTML

First, install man2html from the official repositories.

Now, convert a man page:

$ man free | man2html -compress -cgiurl man$section/$title.$section$subsection.html > ~/man/free.html

Another use for man2html is exporting to raw, printer-friendly text:

$ man free | man2html -bare > ~/free.txt

The GNU implementation of man in the Arch repositories also has the ability to do this on its own:

$ man -H free

This will read your BROWSER environment variable to determine the browser. You can override this by passing the binary to the -H option.

Converting to PDF

man pages have always been printable: they are written in troff, which is fundamentally a typesetting language. If you have ghostscript installed, converting a man page to PDF is actually very easy: man -t <manpage> | ps2pdf - <pdf>. This google image search should give you an idea of what the result looks like; it may not be to everybody's liking.

Caveats: Fonts are generally limited to Times at hardcoded sizes. There are no hyperlinks. Some man pages were specifically designed for terminal viewing, and won't look right in PS or PDF form.

The following perl script converts man pages to PDFs, caches the PDFs in the $HOME/.manpdf/ directory, and calls a PDF viewer, specifically mupdf.

Usage: manpdf [<section>] <manpage>
#!/usr/bin/perl
use File::stat;

$pdfdir = $ENV{"HOME"}."/.manpdf";
-d $pdfdir || mkdir $pdfdir || die "can't create $pdfdir";
$manpage = $ARGV[0];
chop($manpath = `man -w $manpage`);
die if $?;

$maninfo = stat($manpath) or die;
$manpath =~ s@.*/man./(.*)(\.(gz|bz2))?$@$1@;
$pdfpath = "$pdfdir/$manpath.pdf";
$pdftime = 0;
if (-f $pdfpath) {
    $pdfinfo = stat($pdfpath) or die;
    $pdftime = $pdfinfo->mtime;
}
if (!-f $pdfpath || $maninfo->mtime > $pdftime) {
    system "man -t $manpage | ps2pdf -dPDFSETTINGS=/screen - $pdfpath";
}
die if !-f $pdfpath;
if (!fork) {
    open(STDOUT, "/dev/null");
    open(STDERR, "/dev/null");
    exec "mupdf", "-r", "96", $pdfpath;
    #exec "acroread", $pdfpath;
}

Online Man Pages

There are several online databases of man pages, including:

Noteworthy manpages

Here follows a non-exhaustive list of noteworthy pages that might help you understand a lot of things more in-depth. Some of them might serve as a good reference (like the ascii table).

  • ascii(7)
  • boot(7)
  • charsets(7)
  • chmod(1)
  • credentials(7)
  • fstab(5)
  • hier(7)
  • systemd(1)
  • locale(1P)(5)(7)
  • printf(3)
  • proc(5)
  • regex(7)
  • signal(7)
  • term(5)(7)
  • termcap(5)
  • terminfo(5)
  • utf-8(7)

More generally, have a look at category 7 pages:

$ man -s 7 -k ".*" 

Arch Linux specific pages:

  • archlinux(7)
  • mkinitcpio(8)
  • pacman(8)
  • pacman-key(8)
  • pacman.conf(5)

See also