subprocess - Mailx won't send through python

Question

I'm rewriting a shell script to python and a part of it includes sending notifications via mailx. I can't seem to get the subprocess right.

result = subprocess.run(["/bin/mailx", "-r", "sender@email.com", "-s", "Test", "recipient@email.com"], check=True)

When I run this on the server the command returns a blank row, "won't complete" and I thought it might be because mailx is waiting for the email body because when I try sending through bash without a body I get sort of the same problem, so I got these tips:

1. result = subprocess.run(["echo", "Testing", "|", /bin/mailx", "-r", "sender@email.com", "-s", "Test", "recipient@email.com"], check=True) and
2. result = subprocess.run(["/bin/mailx", "-r", "sender@email.com", "-s", "Test", "recipient@email.com", b"Testingtesting"], check=True)

When testing 1, it just echoes out everything after echo. When testing 2, I get the blank row again.

question from:https://stackoverflow.com/questions/65934654/mailx-wont-send-through-python

Answer 1

Using subprocess.Popen you can do it as below :

import subprocess
cmd = """
        echo 'Message Body' | mailx -s 'Message Title' -r sender@someone.com receiver@example.com 
      """

result = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE)
output, errors = result.communicate()

Regarding shell=True from documentation

shell=False disables all shell based features, but does not suffer from this vulnerability; see the Note in the Popen constructor documentation for helpful hints in getting shell=False to work. The use of shell=True is strongly discouraged in cases where the command string is constructed from external input

In your case, if you are not taking user input to pass it to subprocess.Popen you are safe.