UMASK(2)

NAME
umask - set file creation mode mask

SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
mode_t
umask(mode_t numask);

DESCRIPTION
The umask() routine sets the process's file mode creation mask to numask and returns the previous value of the mask. Only the read, write, and execute file permission bits of numask are honored, all others are ignored.

The file mode creation mask is used by the bind(2), mkdir(2), mkdirat(2), mkfifo(2), mkfifoat(2), mknod(2), mknodat(2), open(2) and openat(2) system calls to turn off corresponding bits requested in the file mode (see chmod(2)). This clearing allows users to restrict the default access to their 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.

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

STANDARDS
The umask() function conforms to p1003.1-2008.

HISTORY
The umask() system call first appeared in AT&T UNIX.