umask - set file creation mask
mode_t umask(mode_t mask);
umask sets the umask to mask & 0777.
The umask is used by open(2) to set initial file permis
sions on a newly-created file. Specifically, permissions
in the umask are turned off from the mode argument to
open(2) (so, for example, the common umask default value
of 022 results in new files being created with permissions
0666 & ~022 = 0644 = rw-r--r-- in the usual case where the
mode is specified as 0666).
This system call always succeeds and the previous value of
the mask is returned.
SVr4, SVID, POSIX, X/OPEN, BSD 4.3