| mkdir | [ -p] [-mmode] directory_name ... | 
mkdir creates the directories named as operands, in the
  order specified, using mode rwxrwxrwx (0777) as
  modified by the current umask(2).
The options are as follows:
  - -m
- Set the file permission bits of the final created directory to the
      specified mode. The mode argument can be in any of the formats specified
      to the chmod(1) utility. If a
      symbolic mode is specified, the operation characters “+” and
      “-” are interpreted relative to an initial mode of
      “a=rwx”.
- -p
- Create intermediate directories as required. If this option is not
      specified, the full path prefix of each operand must already exist.
      Intermediate directories are created with permission bits of
      rwxrwxrwx (0777)as modified by the current umask,
      plus write and search permission for the owner. Do not consider it an
      error if the argument directory already exists.
The user must have write permission in the parent directory.
The mkdir utility exits 0 on success,
  and >0 if an error occurs.
The mkdir utility is expected to be
  IEEE Std 1003.2 (“POSIX.2”) compatible.
A mkdir utility appeared in
  Version 1 AT&T UNIX.