Set the shell process’s file creation mask to mode.
instead of specifying which permission to set, it specify which permission to mask or clear from default
If mode begins with a digit, it is interpreted as an octal number;
if not, it is interpreted as a symbolic mode mask similar to that accepted by the chmod command.
If mode is omitted, the current value of the mask is printed.
Note that when the mode is interpreted as an octal number, each number of the umask is subtracted from 7. Thus, a umask of 022 (no write for group and others) results in permissions of 755.
Synopsis:
umask [-p] [-S] [mode]
List of options:
If the -S option is supplied without a mode argument, the mask is printed in a symbolic format.
If the -p option is supplied, and mode is omitted, the output is in a form that may be reused as input.