umask()

Set the file-mode creation mask for the process

Synopsis:

#include <sys/types.h>
#include <sys/stat.h>

mode_t umask( mode_t cmask );

Arguments:

cmask

The new file-mode creation mask; that is, the permissions that you don't want set when the process creates a file. The mask is a combination of these bits:

Owner	Group	Others	Permission
S_IRUSR	S_IRGRP	S_IROTH	Read
S_IRWXU	S_IRWXG	S_IRWXO	Read, write, execute/search. A bitwise inclusive OR of the other three constants. (S_IRWXU is OR of IRUSR, S_IWSUR and S_IXUSR.)
S_IWUSR	S_IWGRP	S_IWOTH	Write
S_IXUSR	S_IXGRP	S_IXOTH	Execute/search

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The umask() function sets the process's file-mode creation mask to cmask, and returns the previous value of the mask. Only the file permission bits (as defined in <sys/stat.h>) are used.

The file-mode creation mask for the process is used when you call creat(), mkdir(), mkfifo(), and open(), to turn off permission bits in the mode argument supplied. Bit positions set in cmask are cleared in the mode of the created file.

Returns:

The previous value of the file-mode creation mask.

Examples:

/*
 * Set the umask to RW for owner,group; R for other
 */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>

int main( void )
  {
    mode_t omask;
    mode_t nmask;

    nmask = S_IRUSR | S_IWUSR | /* owner read write */
            S_IRGRP | S_IWGRP | /* group read write */
            S_IROTH;            /* other read */
    omask = umask( nmask );
    printf( "Mask changed from %o to %o\n",
             omask, nmask );
    return EXIT_SUCCESS;
  }

Classification:

POSIX 1003.1

See also:

chmod(), creat(), mkdir(), mkfifo(), open(), stat()