从 python 脚本在后台执行 Linux 命令

Question

I have an ubuntu machine where kubernetes cluster is running. I am basically trying to run a Kubernetes command in background from python3 script but it's not working, please help...

Below is a part of code from a larger script, I am creating cmd4 using a formatted string and then passing cmd4 to os.system as os.system(cmd4). But as soon as I execute the script it starts showing logs in cmdline. I tried this using nohup as well as mentioned below but it starts populating logs in nohup.out.

for podname in pod_names:
    if "smf" in podname or "pcf" in podname or "udm" in podname:
        containername = 'worker'
    else:
        containername = 'cppe'

    **cmd4 = f"kubectl logs -f -n core {podname} --container={containername} > {podname}_{containername}_log </dev/null &>/dev/null &&"**
    cmd5 = f"echo $! >> pid.txt"
    os.system(cmd4)
    os.system(cmd5)
    pid_file = open('pid.txt', 'a+')
    pid_file.write("\n")
    pid_file.close

=================================

tried with nohup as:

cmd4 = f"nohup kubectl logs -f -n core {podname} --container={containername} > {podname}_{containername}_log </dev/null &>/dev/null &&"

But it gives this o/p

updatedReplicas: 1

deployment.apps/core-pcf configured nohup: ignoring input and appending output to 'nohup.out'

Answer 1

Have you tried using the subprocess library?

I think the solution for your script will be the following.

import subprocess

for podname in pod_names:
    if "smf" in podname or "pcf" in podname or "udm" in podname:
        containername = 'worker'
    else:
        containername = 'cppe'

    **cmd4 = f"kubectl logs -f -n core {podname} --container={containername} > {podname}_{containername}_log </dev/null &>/dev/null &&"**
    cmd5 = f"echo $! >> pid.txt"
    cmd4_bash = subprocess.Popen(cmd4.split(), stdout=subprocess.PIPE)
    cmd5_bash = subprocess.Popen(cmd5.split(), stdout=subprocess.PIPE) 
    pid_file = open('pid.txt', 'a+')
    pid_file.write("\n")
    pid_file.close