About files and directories

Getting help on the command line

Extensive online help is provided by the man(1) system. man is short for ``manual'', and is a tool for retrieving the text of the reference manuals.

In this book, you will sometimes see reference keywords followed by a code in brackets; for example, ls(1) or acct(1M). The code in brackets indicates the section of the reference manual in which the keyword is discussed. If you are working at the shell prompt, you can read the reference entry for the keyword by entering the following command:

man [section] keyword

The section field is optional and is used to select a particular section when a keyword is documented in more than one section. For example, type man 1 passwd to read the 1 section entry on the keyword passwd (which is documented as a command in section 1 and a file in section 4).

The reference manual entries are technical descriptions; they are not tutorials and make no concessions to the inexperienced user.

Getting help when you are uncertain of the topic

If you know the keyword but do not want to read all the reference text, you can use the whatis(1bsd) command to list the description of the item. For example, to read the description of man, type the following:

   $ whatis man
   man (1)    - display reference manual pages; find reference pages by keyword
   man (5)    - macros to format Reference Manual pages

If you are not sure of the keyword to use for a topic, you can use the apropos(1bsd) command (which is the same as man -k). Each entry in the reference manual has a description associated with it; apropos searches the descriptions for the word you give as a subject. For example, to find reference entries concerned with searching, type apropos search. The following entries are among those displayed:

   acctcom (1)      - search and print process accounting file(s)
   fgrep (1)        - search a file for a character string
   grep, egrep (1)  - search a file for a pattern

You can then use man C grep, for example, to display the manual page on the grep command.