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.