GETUMASK(3) Linux Programmer's Manual GETUMASK(3)

getumask - get file creation mask

#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <sys/types.h>
#include <sys/stat.h>
mode_t getumask(void);

This function returns the current file creation mask. It is equivalent to

mode_t getumask(void)
    mode_t mask = umask( 0 );
    return mask;

except that it is documented to be thread-safe (that is, shares a lock with the umask(2) library call).

This is a vaporware GNU extension.

This function is documented in the glibc manual, but, as at glibc version 2.24, it is not implemented on Linux. (See umask(2) for a thread-safe method of discovering a process's umask.)

2017-09-15 GNU