umask(2) [osf1 man page]

umask(2)							System Calls Manual							  umask(2)

NAME

       umask - Sets and gets the value of the file creation mask

SYNOPSIS

       #include <sys/types.h>

       #include <sys/stat.h>

       mode_t umask (	   mode_t cmask );

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       umask():  POSIX.1, XPG4, XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Specifies the value of the file mode creation mask.

DESCRIPTION

       The  umask() function sets the file mode creation mask of the process to the value of the cmask parameter and returns the previous value of
       the mask.  The cmask parameter is constructed by logically ORing file permission bits defined in the sys/mode.h header file.

       Whenever a file is created (by the open(), mkdir(), or mknod() function), all file permission bits set in the file mode creation  mask  are
       cleared in the mode of the created file. This clearing lets users restrict the default access to their files.

       The mask is inherited by child processes.

RETURN VALUES

       Upon successful completion, the previous value of the file mode creation mask is returned.

RELATED INFORMATION

       Commands:  chmod(1), mkdir(1), Bourne shell sh(1b), POSIX shell sh(1p), umask(1)

       Functions:  chmod(2), mkdir(2), mknod(2), open(2), stat(2)

       Standards:  standards(5)

       delim off

																	  umask(2)

UMASK(2)						     Linux Programmer's Manual							  UMASK(2)

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 process's 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

       (octal 0666) when creating a new file, the permissions on the resulting file will be:

	   S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH

       (because 0666 & ~022 = 0644; i.e., rw-r--r--).

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 parent's 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

       This page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2008-01-09								  UMASK(2)