NAME
umask - set file mode creation mask
SYNOPSIS
#include <sys/types.h> #include <sys/stat.h>
mode_t umask(mode_t mask);
DESCRIPTION
umask() sets the calling processs file mode creation mask (umask) to mask & 0777 (i.e., only the file permission bits of mask are used), and returns the previous value of the mask.
The umask is used by open(2), mkdir(2), and other system calls that create files to modify the permissions placed on newly created files or directories. Specifically, permissions in the umask are turned off from the mode argument to open(2) and mkdir(2).
The constants that should be used to specify mask are described under stat(2).
The typical default value for the process umask is
S_IWGRP | S_IWOTH (octal 022).
In the usual case where the
mode argument to
open(2)
is specified as:
S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH
S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH
RETURN VALUE
This system call always succeeds and the previous value of the mask is returned.
CONFORMING TO
SVr4, 4.3BSD, POSIX.1-2001.
NOTES
A child process created via fork(2) inherits its parents umask. The umask is left unchanged by execve(2).
The umask setting also affects the permissions assigned to POSIX IPC objects (mq_open(3), sem_open(3), shm_open(3)), FIFOs (mkfifo(3)), and Unix domain sockets (unix(7)) created by the process. The umask does not affect the permissions assigned to System V IPC objects created by the process (using msgget(2), semget(2), shmget(2)).
SEE ALSO
chmod(2), mkdir(2), open(2), stat(2)
COLOPHON
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