I've written a command line utility that uses getopt for parsing arguments given on the command line. I would also like to have a filename be an optional argument, such as it is in other utilities like grep, cut etc. So, I would like it to have the following usage

tool -d character -f integer [filename]

How can I implement the following?

  • if a filename is given, read from the file.
  • if a filename is not given, read from STDIN.
python file command-line arguments stdin
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