bsd man page for umask

UMASK(2)							System Calls Manual							  UMASK(2)

NAME
       umask - set file creation mode mask

SYNOPSIS
       oumask = umask(numask)
       int oumask, numask;

DESCRIPTION
       Umask  sets the process's file mode creation mask to numask and returns the previous value of the mask.	The low-order 9 bits of numask are
       used whenever a file is created, clearing corresponding bits in the file mode (see chmod(2)).  This clearing allows each user  to  restrict
       the default access to his files.

       The value is initially 022 (write access for owner only).  The mask is inherited by child processes.

RETURN VALUE
       The previous value of the file mode mask is returned by the call.

SEE ALSO
       chmod(2), mknod(2), open(2)

4th Berkeley Distribution					    May 9, 1985 							  UMASK(2)