umask(2)                                                 umask(2)



     NAME
          umask - set and get file creation mask

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

     DESCRIPTION
          umask sets the file-mode-creation mask of the calling pro-
          cess to cmask and returns the previous value of the mask.
          Only the low-order 9 bits of cmask and the file-mode-
          creation mask are used.

          The file-mode-creation mask is used whenever a file is
          created by creat(2), mknod(2) or open(2).  The actual mode
          (see chmod(2)) of the newly created file is the difference
          between the given mode and cmask.  In other words, cmask
          shows the bits to be turned off when a new file is created.

          For the POSIX environment, the following constants for cmask
          are defined in <sys/stat.h>:

          S_IRUSR        read permission, owner

          S_IWUSR        write permission, owner

          S_IXUSR        execute/search permission, owner

          S_IRGRP        read permission, group

          S_IWGRP        write permission, group

          S_IXGRP        execute/search permission, group

          S_IRUSR        read permission, others

          S_IWUSR        write permission, others

          S_IXUSR        execute/search permission, others

          The previous value of cmask is returned by the call.  The
          value is initially 022, which is an octal ``mask'' number
          representing the complement of the desired mode.  The value
          022 here means that no permissions are withheld from the
          owner, but write permission is forbidden to the group and to
          others. Its complement, the mode of the file, would be 0755.
          The file-mode-creation mask is inherited by child processes.






     April, 1990                                                     1

     umask(2)                                                 umask(2)



     RETURN VALUE
          The previous value of the file-mode-creation mask is re-
          turned.

     SEE ALSO
          csh(1), ksh(1), chmod(1), mkdir(1), sh(1), chmod1(2),
          creat(2), mknod(2), open(2).
















































     2                                                     April, 1990