CODEWITHSUNDEEP
python
David Doria
David Doria

Reputation: 10273

Persistent subprocess.Popen session

I am trying to run a command, then later run another command in the same environment (say if I set an environment variable in the first command, I want it to be available to the second command). I tried this:

import subprocess

process = subprocess.Popen("echo \"test\"", shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE);

process.stdin.write("echo \"two\"\n")
process.stdin.flush()

stdout, stderr = process.communicate()
print "stdout: " + stdout
print "stderr: " + stderr

but the output is:

stdout: test

stderr:

Where I'd hope for it to be something like:

stdout: test
two

stderr:

Can anyone see what is wrong?

Upvotes: 2

Views: 5273

Answers (1)

merlin2011
merlin2011

Reputation: 75579

The problem is that you are writing to the stdin of the process echo, which is not reading from its stdin, rather than to something like bash which continues to read stdin. To get the effect you want, look at the following code:

import subprocess
process = subprocess.Popen("/bin/bash", shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE);

process.stdin.write("echo \"test\"\n")
process.stdin.write("echo \"two\"\n")
process.stdin.flush()

stdout, stderr = process.communicate()
print "stdout: " + stdout
print "stderr: " + stderr

Output:

stdout: test
two

stderr:

Update: Take a look at this question to resolve the streaming output issue.

Upvotes: 3

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