redhat man page for umask

UMASK(2)						     Linux Programmer's Manual							  UMASK(2)

NAME
       umask - set file creation mask

SYNOPSIS
       #include <sys/types.h>
       #include <sys/stat.h>

       mode_t umask(mode_t mask);

DESCRIPTION
       umask sets the umask to mask & 0777.

       The  umask  is  used by open(2) to set initial file permissions 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  per-
       missions 0666 & ~022 = 0644 = rw-r--r-- in the usual case where the mode is specified as 0666).

RETURN VALUE
       This system call always succeeds and the previous value of the mask is returned.

CONFORMING TO
       SVr4, SVID, POSIX, X/OPEN, BSD 4.3

SEE ALSO
       creat(2), open(2)

Linux								    1998-08-09								  UMASK(2)