Its umask and not unmask. You can find more documentation on it by refering to the bash_builtins via the umask manpages. Try man umask on your console. Its a good doc, very yummy. I'd recommend reading it entirely. For what its worth, here's the scoop from ~ line 1450 or so.

       umask [-p] [-S] [mode]
              The user file-creation mask is  set  to  mode.   If
              mode  begins  with a digit, it is interpreted as an
              octal number; otherwise it is interpreted as a sym­
              bolic   mode  mask  similar  to  that  accepted  by
              chmod(1).  If mode is omitted, or if the -S  option
              is  supplied,  the  current  value  of  the mask is
              printed.  The -S  option  causes  the  mask  to  be
              printed  in symbolic form; the default output is an
              octal number.  If the -p option  is  supplied,  and
              mode  is  omitted, the output is in a form that may
              be reused as input.  The return status is 0 if  the
              mode  was  successfully changed or if no mode argu­
              ment was supplied, and false otherwise.
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HTH!

#!/home/bbq/bin/perl
# Trust no1!