Unix manual

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Almost all substantial UNIX and Unix-like operating systems have extensive documentation known as man pages (short for "manual pages"). The Unix command used to display them is man. Each page is a self-contained document.

To read a page from the manual, one can use the command

$ man <page_name>

at a shell prompt, for example, "man ftp". Pages are traditionally referred to using the notation "page_name(section)", for example, ftp(1).

The same page name may appear in more than one section of the manual. This can occur when the names of system calls, user commands, or macro packages conflict. Two examples are man(1) and man(7), or exit(1) and exit(3). The syntax for accessing the non-default manual section varies between different man implementations. On Linux, for example, the syntax for reading printf(3) is

 $ man 3 printf

The UNIX Programmer's Manual was first published on November 3, 1971. At the time of its development in the 1970s, the availability of online documentation through the manual page system was regarded as a great advance. To this day, virtually every Unix command line application comes with its man page, and many Unix users perceive the lack of man pages as a sign of low quality. However, the format of a single page for each application, the lack of classification within the sections and the relatively unsophisticated formatting facilities has motivated the development of alternative documentation systems. Few have enjoyed much popularity, with the possible exception of the GNU project's "info" system, a simple hypertext system.

Most Unix GUI applications (particularly those built using the GNOME and KDE development environments) now provide end-user documentation in HTML and include embedded HTML viewers for viewing the help within the application.

Usually the man pages are written in English. Translations into other languages can be also available on the system, in which case the version best fitting the user preferences is displayed.

The default format of the man pages is troff, with either the macro package man (appearance oriented) or mdoc (semantic oriented). This makes it possible to typeset a man page to PostScript, PDF and various other formats for viewing or printing (although most users still prefer the default terminal interface).

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Manual sections

The manual is generally split into eight numbered sections, organised as follows (on BSD Unix and Linux):

Section	Description
1	General commands
2	System calls
3	C library functions
4	Special files (usually devices, those found in /dev)
5	File formats and conventions
6	Games
7	Miscellanea
8	System administration commands and daemons

Note that Unix System V uses a similar numbering scheme, except section 4 is file formats, section 5 is miscellany and section 7 is special files. The sections are further subdivided by means of a suffix letter, such that section 3C is for C library calls, 3M is for the math library, and so on. A consequence of this is that section 8, the system administration commands is relegated to the 1M subsection of the main commands section.

On some systems some of the following sections are available: