Basic Linux Commands

Ample and extensive information and documentation about the OS, related commands, utilities, and packages is available both on the Linux OS itself and sources like the Internet. Many distributions like Mandrake, Red Hat, and SuSe provide a GUI based help environment.

All Linux commands are associated with help screens that may be accessed using the man command. Typing the word 'man' (for help manual) followed by a command will return a page of information that describes the command and every option associated with the command. For custom packages and utilities, an 'about' screen with information about version, author and so on will also be part of this display. The less command is internally used to display 'man' pages; the up and down arrow and other navigation keys may be used to move around the help page and pressing the 'q' key will 'quit' the page and bring up the command prompt again.

Man-pages usually begin with a NAME section that contains the name of the command followed by a SYNOPSIS section that contains a brief overview of the command that sometimes includes examples of use. The DESCRIPTION section follows with a detailed overview of the command and the purport of each of its '-' options and other command line parameters. The SEE ALSO section lists related man-pages and additional documentation. The BUGS section contains a list of known errors and other problems associated with the command.

A more descriptive and verbose info command is also available for most commands. The 'info' display for a particular command also contains menus that contain links to the info pages of related items; positioning the cursor under a menu item and pressing the enter key will bring up the info page of the item. The --help command brings up a more concise version of the man page unfiltered by the 'less' command. The entire page is displayed at one go without navigation options; a section by section view is not displayed. A primary source of information about Linux on the Internet is the Linux Documentation Project (LDP). LDP is useful because help is compiled task-wise rather than command-wise.

apropos and whatis are other help commands. The Apropos command searches the man page description section of all commands using its parameters as keywords. A user who does not know the exact command for a directory listing may issue the command 'apropos directory' and all the commands that contain the word directory in the description are returned. The search may be restricted to return a smaller list by adding more keywords or using double quotes to look for word combinations. The whatis command follows the syntax 'whatis Linux_command' which returns a short description of Linux_command. The whereis command takes command keywords as arguments and returns the filesystem location of the executable, source code, and man pages of the specified keyword

Notes:

1. The number found within a parenthesis after the Linux command on its man page represents the actual section of the manual that contains the page.
2. Issuing 'man Help_Command' will bring up the manual page for the help command itself.