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To: python-list@python.org
From: Robert Kern <robert.kern@gmail.com>
Subject: Re: Question About Command line arguments
Date: Fri, 10 Jun 2011 14:27:10 -0500
Organization: The Church of Last Thursday
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On 6/10/11 12:58 PM, Mark Phillips wrote:
> On Fri, Jun 10, 2011 at 10:41 AM, MRAB <python@mrabarnett.plus.com
> <mailto:python@mrabarnett.plus.com>> wrote:
>
>     On 10/06/2011 18:21, Mark Phillips wrote:
>
>         I have a script that processes command line arguments
>
>         def main(argv=None):
>              syslog.syslog("Sparkler stared processing")
>              if argv is None:
>                  argv = sys.argv
>              if len(argv) != 2:
>                  syslog.syslog(usage())
>              else:
>                  r = parseMsg(sys.argv[1])
>                  syslog.syslog(r)
>              return 0
>
>         if __name__ == "__main__":
>              sys.exit(main())
>
>         When I run "python myscript fred" it works as expected - the argument
>         fred is processed in parseMsg as sys.arv[1]
>
>         When I run "echo fred | python myscript" the script thinks there are no
>         arguments, so it prints out the usage statement.
>
>         Is the problem with the echo command, or how I wrote my script?
>
>     In the second case, there aren't any arguments. The echo command is
>     writing "fred" to its standard output, which is attached to your
>     script's standard input.
>
> How do I write my script so it picks up argument from the output of commands
> that pipe input into my script?

You may want to just use the appropriate shell syntax instead:

   $ python myscript `echo fred`

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco