UMASK(2) BSD System Calls Manual UMASK(2)
umask -- set file creation mode mask
The umask() routine sets the process's file mode creation mask to numask
and returns the previous value of the mask. The 9 low-order access per-
mission bits of numask are used by system calls, including open(2),
mkdir(2), mkfifo(2) and mknod(2) to turn off corresponding bits requested
in the 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.
The previous value of the file mode mask is returned by the call.
The umask() function is always successful.
chmod(2), mkdir(2), mkfifo(2), mknod(2), open(2)
The umask() function conforms to IEEE Std 1003.1-2008 (``POSIX.1'').
The umask() system call first appeared in Version 7 AT&T UNIX.
BSD April 28, 2017 BSD