Get Help With A Command

The --help argument is a common choice for quickly learning about a command. Particularly useful, --help shows the arguments for that particular command so we don’t have to look them up online.

Another option is the whatis command, which prints a one-line description of the command.

Quickly Describe A Command

whatis mkdir
mkdir (1)            - make directories
mkdir (2)            - create a directory

Note that in this case there are two mkdir commands with slightly different descriptions, but you can ignore that.

Get Help With A Command

In this example, we get help for the command mkdir (make directory).

mkdir --help
Usage: mkdir [OPTION]... DIRECTORY...
Create the DIRECTORY(ies), if they do not already exist.

Mandatory arguments to long options are mandatory for short options too.
  -m, --mode=MODE   set file mode (as in chmod), not a=rwx - umask
  -p, --parents     no error if existing, make parent directories as needed
  -v, --verbose     print a message for each created directory
  -Z                   set SELinux security context of each created directory
                         to the default type
      --context[=CTX]  like -Z, or if CTX is specified then set the SELinux
                         or SMACK security context to CTX
      --help     display this help and exit
      --version  output version information and exit

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: <http://www.gnu.org/software/coreutils/mkdir>
or available locally via: info '(coreutils) mkdir invocation'