[root@localhost build]# mkdir -help
mkdir: invalid option -- 'h'
Try 'mkdir --help' for more information.
[root@localhost build]# 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/>
For complete documentation, run: info coreutils 'mkdir invocation'
[root@localhost build]#