umask(2) System Calls Manual umask(2) umask - LIBRARY Standard C library (libc, -lc) #include mode_t umask(mode_t mask); umask() (umask) mask & 0777 (.. mask ) . umask open(2), mkdir(2) , , , . , umask mode open(2) mkdir(2). , ACL ( acl(5)), umask , ACL , ACL, , mode, . , ACL umask 022: u::rwx,g::r-x,o::r-x ACL mode 0666 (rw-rw-rw-) 0644 (rw-r--r--). , mask, inode(7). umask S_IWGRP | S_IWOTH ( 022). , mode open(2) : S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH ( 0666) , : S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH (because 0666 & ~022 = 0644; i.e. rw-r--r--). . POSIX.1-2008. POSIX.1-2001, SVr4, 4.3BSD. , fork(2), umask . umask execve(2). umask() umask . umask umask(). . Linux 4.7 umask Umask /proc/pid/status. /proc/self/status umask . umask , IPC- POSIX (mq_open(3), sem_open(3), shm_open(3)), FIFO (mkfifo(3)) UNIX (unix(7)), . umask , IPC- System V, ( msgget(2), semget(2), shmget(2)). . chmod(2), mkdir(2), open(2), stat(2), acl(5) Azamat Hackimov , Dmitriy Ovchinnikov , Dmitry Bolkhovskikh , Katrin Kutepova , Yuri Kozlov ; GNU 3 , . . , , . Linux man-pages 6.06 31 2023 . umask(2)