Unix manual

From Academic Kids

Almost all substantial UNIX and Unix-like operating systems (*nix) have extensive online 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 with independent copyright status.

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

$ man [<section>] <page_name>

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

The section number is used to allow a specific manual page to be chosen when there are multiple manual pages with the same name. 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).

At the time of its development in the 1970's, the availability of online documentation through the manual page system was regarded as a great advance. However, the format of a single page for each application is unsuitable for complex, interactive applications, and the formatting facilities provided for man pages are relatively unsophisticated, not supporting the inclusion of graphics for screen shots, for instance. As applications became more complex, and computer users became less tolerant of poor documentation, the man page system was shown to be inadequate for many purposes and successors began to be developed.

Virtually all Unix variants continue to support man pages, but for many programs they are no longer the primary form of online documentation and help. An early attempt to replace them was the GNU project's "info" system, a primitive hypertext system. Most Unix GUI applications (particularly those built using the GNOME and KDE development environments), and many others, now provide end-user documentation in HTML and include embedded HTML viewers for viewing the help within the application.

On Microsoft Windows man pages can be viewed using the WinElvis editor.

Manual sections

The manual is generally split into eight numbered sections, organised as follows:

Section Description
1 General commands
2 Low-level 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 and associated commands

On some systems some of three other sections are available:

Section Description
9 Kernel routines (obsolete)
n Tcl/Tk keywords
x The X Window System

The manual pages are stored as nroff source files. Most versions of man cache the formatted versions of the last several pages viewed.

For an example of a man page see chmod. To see other options you can use with command man, enter the command man man.

References

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.

External links

pt:Página de manual

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