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On-line Help

In general, there are many more command line switches available for each command than you have seen so far and certainly more than I have space to include here. If you need to find extra detail about the use and format of anything covered in this book, or any other system facility for that matter, then there is a terrific amount of information available in the form of the on-line manual. Linux has a set of manual pages available that are split into sections. The purpose of the pages in each section is as follows:

A command which allows access to all these manual pages is called man. It is used as follows:

	$ man ls

This will give a listing of the manual page for the ls command. Because most manual pages are longer than a screen in length, the man command will use the more command (or less) to split its output into screens. Each manual page is split up into several parts. Typically these include:

Normally, when you ask to see a particular manual entry, the manual is searched sequentially starting with section 1, and it is the first occurrence of the required item which gets displayed. Sometimes, a particular item may occur in more than one manual section. One example of this, which you have already encountered, is the item passwd. This occurs not only in manual section 1 as the passwd command used to change passwords, but also in section 5, where the format of the passwd file in /etc is discussed. If you just enter the command:

	$ man passwd

you will always get the section 1 entry if it exists. In order to see the manual entry in a specific manual section you need to give this as an optional parameter to the man command. The following example will list the section 5 passwd entry:

	$ man 5 passwd

It is also possible to list any relevant entries in all sections of the manual with the -a switch:

	$ man -a passwd

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