kill process with python

Question

I need to make a script that gets from the user the following:

1) Process name (on linux).

2) The log file name that this process write to it.

It needs to kill the process and verify that the process is down. Change the log file name to a new file name with the time and date. And then run the process again, verify that it's up in order it will continue to write to the log file.

Thanks in advance for the help.

Solution 1

You can retrieve the process id (PID) given it name using pgrep command like this:

import subprocess
import signal
import os
from datetime import datetime as dt


process_name = sys.argv[1]
log_file_name = sys.argv[2]


proc = subprocess.Popen(["pgrep", process_name], stdout=subprocess.PIPE) 

# Kill process.
for pid in proc.stdout:
    os.kill(int(pid), signal.SIGTERM)
    # Check if the process that we killed is alive.
    try: 
       os.kill(int(pid), 0)
       raise Exception("""wasn't able to kill the process 
                          HINT:use signal.SIGKILL or signal.SIGABORT""")
    except OSError as ex:
       continue

# Save old logging file and create a new one.
os.system("cp {0} '{0}-dup-{1}'".format(log_file_name, dt.now()))

# Empty the logging file.
with open(log_file_name, "w") as f:
    pass

# Run the process again.
os.sytsem("<command to run the process>") 
# you can use os.exec* if you want to replace this process with the new one which i think is much better in this case.

# the os.system() or os.exec* call will failed if something go wrong like this you can check if the process is runninh again.

Hope this can help

Solution 2

If you know how to do it in the terminal, then you could use the following:

import os
os.system("your_command_here; second_command; third; etc")

So that you end up having sort of a mini shell script inside python. I would also consider making this shell script exist on its own and then call it from python:

import os
os.system("path/to/my_script.sh")

Cheers!

Comments

[snarkyname77]

I like the simplicity, and have one thing to add 'os.system' returns the exit status code so you can check for the success of the process and handle errors by code.

[James Broadhead]

Generally, programmers are discouraged from using os.system any more, since subprocess.Popen gives many more options and support. In particular, it handles command-line arguments much better and allows piping output.