usage: ./cert-retrieve <arguments>
      version: V1-7
        -certnum <certificate serial number > OR
                    - url <entire url that was mailed to you>
       -dir <directory for the usercert and key, defaults to /home/olson/.globus>
       -keyfile  <name of keyfile for private key corresponding to this cert>
       -prefix  causes the key and cert files to be named <prefix>cert.pem
                and <prefix>key.pem rather than usercert.pem and userkey.pem.
       -ca  <name of CA to use, either 'test' or 'doegrids'>
       -debug prints what it is doing
       -help  prints this message
       -V  prints package version and exits
       any omitted argruments will be prompted for
  This software is contributed to the DOEGrids PKI and is supported by
  the PPDG RA.  Please send any questions, comments, problems to
  ra@ppdg.net and/or dlolson@lbl.gov.


  Side effects:
    Generates some temporary files that get removed in normal operation.
    Relies on files produced by cert-request.pl in order to retrieve the
    corresponding certificate.