mode_t umask (
mode_t cmask );
Interfaces documented on this reference page conform to industry standards as follows:
umask(): POSIX.1, XPG4, XPG4-UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
Specifies the value of the file mode creation mask.
The umask() function sets the file mode creation mask of the process to the value of the cmask parameter and returns the previous value of the mask. The cmask parameter is constructed by logically ORing file permission bits defined in the sys/mode.h header file.
Whenever a file is created (by the open(), mkdir(), or mknod() function), all file permission bits set in the file mode creation mask are cleared in the mode of the created file. This clearing lets users restrict the default access to their files.
The mask is inherited by child processes.
Upon successful completion, the previous value of the file mode creation mask is returned.
Commands: chmod(1), mkdir(1), Bourne shell sh(1b), POSIX shell sh(1p), umask(1)
Functions: chmod(2), mkdir(2), mknod(2), open(2), stat(2)