Umask Filter

It sets the file mode creation mask of the current shell execution environment to the value specified   through the mask operand. That mask affects the initial value of the file permission bits of consequently created files. The current value of the mask is printed if we are giving the command umask alone ( $umask) is given.

umask is recognized and executed through the shell.

umask can be involved in  the  user's  .profile file and invoked at login to set the user's permissions automatically on files or directories made.

umask 022 erased write permission for group and other (files generally created with mode 777 become mode 755; files made with mode 666 become mode 644).

The given options are supported:

-S         Gives symbolic output.

Let's consider the following instance

# umask 027 ( for the current session)

or

$ vi .profile

umask 027

:wq!

Within first case above the umask value is changed for a while. If the user logs out and then again logs in the umask value goes back to the default value. In the other case the new umask value is entered into the .profile  file  of  the  user  that  permanently  modify  the  umask  value  and  thus  changes  the  file permissions consequently.

User have to logout from the current session and again he have to login in order to initialize umask's new value after changing the value of UMASK in the .profile file the.