Can't assign bash variable in python subprocess

user_17949044 0
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I am trying to assign to a variable the fingerprint of a pgp key in a bash subprocess of a python script. Here's a snippet:

import subprocess
subprocess.run(
'''
    export KEYFINGERPRINT="$(gpg --with-colons --fingerprint --list-secret-keys | sed -n 's/^fpr:::::::::\([[:alnum:]]\+\):/\1/p')"
    echo "KEY FINGERPRINT IS: ${KEYFINGERPRINT}"
''',
shell=True, check=True,
executable='/bin/bash')

The code runs but echo shows an empty variable: KEY FINGERPRINT IS: and if I try to use that variable for other commands I get the following error: gpg: key "" not found: Not found

HOWEVER, if I run the same exact two lines of bash code in a bash script, everything works perfectly, and the variable is correctly assigned.

What is my python script missing?

Thank you all in advance.

subprocess gnupg python variables bash
2 Answers

in order to run 2 commands in subprocess you need to run them one after each other or use ;

import subprocess
ret = subprocess.run('export KEYFINGERPRINT="$(gpg --with-colons --fingerprint --list-secret-keys | sed -n 's/^fpr:::::::::\([[:alnum:]]\+\):/\1/p')"; echo "KEY FINGERPRINT IS: ${KEYFINGERPRINT}"', capture_output=True, shell=True)
print(ret.stdout.decode())

you can use popen:

commands = '''
    export KEYFINGERPRINT="$(gpg --with-colons --fingerprint --list-secret-keys | sed -n 's/^fpr:::::::::\([[:alnum:]]\+\):/\1/p')"
    echo "KEY FINGERPRINT IS: ${KEYFINGERPRINT}"
'''
process = subprocess.Popen('/bin/bash', stdin=subprocess.PIPE, stdout=subprocess.PIPE)
out, err = process.communicate(commands)
print out
user_176748490

The problem is the backslashes in your sed command. When you paste those into a Python string, python is escaping the backslashes. To fix this, simply add an r in front of your string to make it a raw string:

import subprocess
subprocess.run(
r'''
    export KEYFINGERPRINT="$(gpg --with-colons --fingerprint --list-secret-keys | sed -n 's/^fpr:::::::::\([[:alnum:]]\+\):/\1/p')"
    echo "KEY FINGERPRINT IS: ${KEYFINGERPRINT}"
''',
shell=True, check=True,
executable='/bin/bash')
user_142707250
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