I have a small Python utility which should be run only as a pipe. I want it to print out the help message when it runs stand alone. How can a process know whether it is being used as a pipe. Comparing sys.stdin and sys.__stdin__ does not work.
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You can use isatty:
if sys.stdin.isatty():
It will be True if standard input is a tty, which roughly means it's being used directly, outside a pipe.
Matthew Flaschen
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2Also `if sys.stdout.isatty()` for the opposite. – isaaclw Jul 30 '14 at 18:36
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1Just a hint: if you start python in a CI environment ala travis, jenkins or gitlab-ci, it might be that `sys.stdin.isatty()` is always `False`. – Mirko Friedenhagen Feb 02 '18 at 12:28