umask \- set file creation mode mask
sets a mask used whenever a file is created by
of the newly-created file is the logical
of the given mode and the complement of the argument.
Only the low-order 9 bits of the mask (the protection bits)
In other words, the mask shows the bits to be turned off
The previous value of the mask is returned by the call.
The value is initially 0 (no restrictions).
The mask is inherited by child processes.
creat(2), mknod(2), chmod(2)