Blog: 2024-02-13: Difference between revisions
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(Created page with "How does this work but it doesn't seem to when you use the read and write methods on the io objects? <pre> proc = subprocess.Popen(['bc'], stdin=subprocess.PIPE, stdout=subprocess.PIPE) os.write(proc.stdin.fileno(), b'100+200\n') print(os.read(proc.stdout.fileno(), 4096)) </pre>") |
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os.write(proc.stdin.fileno(), b'100+200\n') |
os.write(proc.stdin.fileno(), b'100+200\n') |
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print(os.read(proc.stdout.fileno(), 4096)) |
print(os.read(proc.stdout.fileno(), 4096)) |
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</pre>https://stackoverflow.com/questions/39899074/communicate-multiple-times-with-a-subprocess-in-python |
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Ok it was about: buffering and flushing |
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<pre> |
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import os |
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import subprocess |
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proc = subprocess.Popen(['bc'], stdin=subprocess.PIPE, stdout=subprocess.PIPE) |
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proc.stdin.write(b'100+200\n') |
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proc.stdin.flush() |
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print(proc.stdout.readline()) |
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</pre> |
</pre> |
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flush was missing, and readline reads just a line rather than read which blocks |
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Latest revision as of 11:00, 13 February 2024
How does this work but it doesn't seem to when you use the read and write methods on the io objects?
proc = subprocess.Popen(['bc'], stdin=subprocess.PIPE, stdout=subprocess.PIPE) os.write(proc.stdin.fileno(), b'100+200\n') print(os.read(proc.stdout.fileno(), 4096))
https://stackoverflow.com/questions/39899074/communicate-multiple-times-with-a-subprocess-in-python
Ok it was about: buffering and flushing
import os import subprocess proc = subprocess.Popen(['bc'], stdin=subprocess.PIPE, stdout=subprocess.PIPE) proc.stdin.write(b'100+200\n') proc.stdin.flush() print(proc.stdout.readline())
flush was missing, and readline reads just a line rather than read which blocks