Create a special file (a file that can send or receive data). Special files can be character files (read one character at a time), block files (read several characters at a time), or FIFO pipes (see mkfifo).
To choose which type of device to create, use one of the following arguments:
Create a FIFO file (named pipe). You do not need to specify the major and minor device numbers.
Create a block file. You must specify the major and minor device numbers the file represents.
c or u
Create a character file. You must specify the major and minor device numbers the file represents.
Linux's /dev/MAKEDEV utility is useful for creating one or more devices of a given type in a single command.
Print usage information and exit.
Set the file mode of the device, as with chmod. The default mode is a=rw unless you have chosen other settings via umask.