Help

1.10 Help

A feature in bash that no other shell has is an online help system. The help command gives information on commands in bash . If you type help by itself, you'll get a list of the built-in shell commands along with their options.

If you provide help with a shell command name it will give you a detailed description of the command:

$ help cd

cd: cd [-PL] [dir]

 Change the current directory to DIR. The variable $HOME is the

 default DIR. The variable $CDPATH defines the search path for

 the directory containing DIR. Alternative directory names in

 CDPATH are separated by a colon (:). A null directory name is

 the same as the current directory, i.e. `.'. If DIR begins with

 a slash (/), then $CDPATH is not used. If the directory is not

 found, and the shell option `cdable_vars' is set, then try the

 word as a variable name. If that variable has a value, then cd

 to the value of that variable. The -P option says to use the

 physical directory structure instead of following symbolic links;

 the -L option forces symbolic links to be followed.

You can also provide help with a partial name, in which case it will return details on all commands matching the partial name. For example, help re will provide details on read , readonly , and return . The partial name can also include wildcards. You'll need to quote the name to ensure that the wildcard is not expanded to a filename. So the last example is equivalent to help ' re* ' , and help ' re?? ' will only return details on read .

Sometimes help will show more than a screenful of information and it will scroll the screen. You can use the more command to show one screenful at a time by typing help command | more.