osx man page for umask

UMASK(2)						      BSD System Calls Manual							  UMASK(2)

NAME
     umask -- set file creation mode mask

SYNOPSIS
     #include <sys/stat.h>

     mode_t
     umask(mode_t cmask);

DESCRIPTION
     The umask() routine sets the process's file mode creation mask to cmask and returns the previous value of the mask.  The 9 low-order access
     permission bits of cmask are used by system calls, including open(2), mkdir(2), mkfifo(2), and mknod(2) to turn off corresponding bits
     requested in file mode.  (See chmod(2)).  This clearing allows each user to restrict the default access to his files.

     The default mask value is S_IWGRP | S_IWOTH (022, write access for the owner only).  Child processes inherit the mask of the calling process.

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

ERRORS
     The umask() function is always successful.

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

     The include file <sys/types.h> is necessary.

SEE ALSO
     chmod(2), mkdir(2), mkfifo(2), mknod(2), open(2), compat(5)

STANDARDS
     The umask() function call is expected to conform to IEEE Std 1003.1-1988 (``POSIX.1'').

4th Berkeley Distribution					   June 4, 1993 					 4th Berkeley Distribution