Changes the permissions of a list of files.  The first element of the
list must be the numerical mode, which should probably be an octal
number, and which definitely should not be a string of octal digits:
0644
 is okay, '0644'
 is not.  Returns the number of files
successfully changed.  See also oct, if all you have is a string.
On systems that support fchmod, you might pass file handles among the files. On systems that don't support fchmod, passing file handles produces a fatal error at run time.
You can also import the symbolic S_I*
 constants from the Fcntl
module: