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pythonlinuxbashshell

How to store the result of an executed shell command in a variable in python?

I need to store the result of a shell command that I executed in a variable, but I couldn't get it working. I tried like:

import os    

call = os.system("cat syscall_list.txt | grep f89e7000 | awk '{print $2}'")
print call

But it prints the result in terminal and prints the value of call as zero, possibly indicating as success. How to get the result stored in a variable?

Solution

  • Use the subprocess module instead:

    import subprocess
output = subprocess.check_output("cat syscall_list.txt | grep f89e7000 | awk '{print $2}'", shell=True)

    Edit: this is new in Python 2.7. In earlier versions this should work (with the command rewritten as shown below):

    import subprocess
output = subprocess.Popen(['awk', '/f89e7000/ {print $2}', 'syscall_list.txt'], stdout=subprocess.PIPE).communicate()[0]

    As a side note, you can rewrite

    cat syscall_list.txt | grep f89e7000

    To

    grep f89e7000 syscall_list.txt

    And you can even replace the entire statement with a single awk script:

    awk '/f89e7000/ {print $2}' syscall_list.txt

    Leading to:

    import subprocess
output = subprocess.check_output(['awk', '/f89e7000/ {print $2}', 'syscall_list.txt'])