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 All About the umask and Permissions

"Within UNIX, system calls have base permissions (sometimes referred to as "default permissions") with which to create new files and directories. For directories the base permissions are (octal) 777 (rwxrwxrwx), and for files they are 666 (rw-rw-rw). Before creating the file or directory, the base permissions are compared to a mask (the umask set by the umask command) that will "mask out" permission bits to determine the final permissions for the object being created. The calculation to determine the final permissions is to take the binary of the base permissions and perform a logical AND operation on the ones complement representation of the binary umask."

 (Submitted by Noel Sun May 23, 2004 )


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