Learning Linux Shell Scripting - Second Edition

Setuid

Another very interesting functionality is the setuid feature. If the setuid bit is set for a script, then the script will always run with the owner's privileges, irrespective of which user is running the script. If the administrator wants to run a script written by him by other users, then he can set this bit.

Consider either of the following situations:

    $ chmod u+s file_name
    $ chmod 4777 file 

The file permissions after any of the preceding two commands will be drwsrwxrwx.