#include <sys/stat.h>

mode_t umask(mode_t cmask);


Partially implemented


IEEE Std 1003.1-2017


The umask() function shall set the file mode creation mask of the process to cmask and return the previous value of the mask. Only the file permission bits of cmask (see <sys/stat.h>) are used; the meaning of the other bits is implementation-defined.

The file mode creation mask of the process is used to turn off permission bits in the mode argument supplied during calls to the following functions:

  • open(), openat(), creat(), mkdir(), mkdirat(), mkfifo(), and mkfifoat()

  • mknod(), mknodat()

  • mq_open()

  • sem_open()

Bit positions that are set in cmask are cleared in the mode of the created file.

Return value#

The file permission bits in the value returned by umask() shall be the previous value of the file mode creation mask. The state of any other bits in that value is unspecified, except that a subsequent call to umask() with the returned value as cmask shall leave the state of the mask the same as its state before the first call, including any unspecified use of those bits.


No errors are defined.



Known bugs#


See Also#

  1. Standard library functions

  2. Table of Contents