2

How to receive data from the environment e.g. bash

I am trying to launch two Python scripts in bash and pipe stdout from one of them to stdin of the other. The first script outputs a single number every second.

./script1 | ./script2
./script1 > ~/file &; tail -f ~/file

I tried those, but can't get it working. script1 outputs via Python's print, while script2 is tested with echo "21.11 22.23 33.233" | ./script2 and is known to work.

If I terminate script1 ofter some time, and then cat ~/file, I see the actual data. However, at the time of execution, neither of the above examples work.

How do I make this work? I would like to be able to work both with and without intermediate file.

1
  • 1
    you have to flush the output buffer Jan 14, 2014 at 5:22

1 Answer 1

2

In the python script make sure you call:

sys.stdout.flush()

after print-ing. You don't have to do that on each statement, but you have to do it on each group of prints that has to be processed. ( import sys if not done yet).

3
  • Why is that. In the question that I linked to, it is discussed if there is a better way to output data than print. So is there (it's only one print per iteration)?
    – Vorac
    Jan 14, 2014 at 10:25
  • That question is about reading data from stdin, not printing (which writing to sys.stdout)
    – Timo
    Jan 14, 2014 at 10:34
  • Secondly, is print i a proper way to stream data to the environment?
    – Vorac
    Jan 14, 2014 at 10:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.