Question About Command line arguments

[MRAB]

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.