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Kill application in linux using python

I need one help regarding killing application in linux
As manual process I can use command -- ps -ef | grep "app_name" | awk '{print $2}'
It will give me jobids and then I will kill using command " kill -9 jobid".
I want to have python script which can do this task.
I have written code as
import os
os.system("ps -ef | grep app_name | awk '{print $2}'")
this collects jobids. But it is in "int" type. so I am not able to kill the application.
Can you please here?
Thank you

import subprocess
temp = subprocess.run("ps -ef | grep 'app_name' | awk '{print $2}'", stdin=subprocess.PIPE, shell=True, stdout=subprocess.PIPE)
job_ids = temp.stdout.decode("utf-8").strip().split("\n")
# sample job_ids will be: ['59899', '68977', '68979']
# convert them to integers
job_ids = list(map(int, job_ids))
# job_ids = [59899, 68977, 68979]
Then iterate through the job ids and kill them. Use os.kill()
for job_id in job_ids:
os.kill(job_id, 9)
Subprocess.run doc - https://docs.python.org/3/library/subprocess.html#subprocess.run

To kill a process in Python, call os.kill(pid, sig), with sig = 9 (signal number for SIGKILL) and pid = the process ID (PID) to kill.
To get the process ID, use os.popen instead of os.system above. Alternatively, use subprocess.Popen(..., stdout=subprocess.PIPE). In both cases, call the .readline() method, and convert the return value of that to an integer with int(...).

Best way to check if a shell command has executed successfully

import os
val = os.popen("ls | grep a").read()
Let's say I want to check if a given directory has a any file named a. If the directory doesn't have a file with a in it the val is empty and if not val should be assigned with some output gotten from executing that command.
Are there any cases where the value of val could be still something even with empty output? In this case, there are no files with a but could val still have some value? Are there any cases where the output looks empty when we execute on a terminal, but value still has some value (e.g. white space)?
Is it an effective approach to use in general? (I am not really trying to check for files with certain names. This is actually just an example.)
Are there any better ways of doing such a thing?

I'd recommend using python3 subprocess, where you can use the check parameter. Then your command will throw an error if it does not succeed:
import subprocess
proc = subprocess.run(["ls | grep a"], shell=True, check=True, stdout=subprocess.PIPE)
# proc = subprocess.run(["ls | grep a"], shell=True, check=True, capture_output=True) # starting python3.7
print(proc.stdout)
but as #JohnKugelman suggested, in this case you'd better use glob:
import glob
files_with_a = glob.glob("*a*")

If you reallly go for the approach of running a os command from python, I'd recommend using the subprocess package:
import subprocess
command = "ls | grep a"
process = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE)
process.wait()
print(process.returncode)

How to get PID of the subprocess with subprocess check_output

In my python script I'm trying to run some long lasting download process, like in the example below, and need to find a PID of the process started by check_output:
out = subprocess.check_output(["rsync","-azh","file.log",...])
Is it possible to do?

You can run your subprocess using Popen instead:
import subprocess
proc = subprocess.Popen(["rsync","-azh","file.log",...], stdout=subprocess.PIPE)
out = proc.communicate()[0]
pid = proc.pid
Generally, Popen object gives you better control and more info of the subprocess, but requires a bit more to setup. (Not much, though.) You can read more in the official documentation.

To get Parent and ChildProcess ID from process ID in Python

I am trying to get the ppid of the process that I want.
I used following code to get the pid
proc=subprocess.Popen('ps -ae | grep ruby', shell=True, stdout=subprocess.PIPE, )
output=proc.communicate()[0]
str = output.split()
Now in the str[0], I have the pid of the process say ruby, I want to get the parent process ID ppid and child process ID of the same process.
I need this solution to be run on Solaris as well as Red Hat Enterprise Linux 6.0
Is there any way to get that like getppid() and getchildid()? Or do I need to do it by grep command again and splitting?

Using this code is a bad idea. Your code will not work on solaris.
You can use 'psutil' library, that way you can keep your code independent of os.
https://github.com/giampaolo/psutil
p = psutil.Process(7055)
parent_pid = p.ppid()

I presume there's nothing wrong with os.getppid() .
Shrug.
http://docs.python.org/3/library/os.html#process-parameters

The answer depends on your system's ps command. On Linux, ps will include the PPID for each process with the -l flag (among others), so ps -ale | grep ruby will include the ruby process id in str[3] and ruby's PPID in str[4].

obtaining pid of child process

I am using python's multiprocessing module to spawn new process
as follows :
import multiprocessing
import os
d = multiprocessing.Process(target=os.system,args=('iostat 2 > a.txt',))
d.start()
I want to obtain pid of iostat command or the command executed using multiprocessing
module
When I execute :
d.pid
it gives me pid of subshell in which this command is running .
Any help will be valuable .
Thanks in advance

Similar to #rakslice, you can use psutil:
import signal, psutil
def kill_child_processes(parent_pid, sig=signal.SIGTERM):
try:
parent = psutil.Process(parent_pid)
except psutil.NoSuchProcess:
return
children = parent.children(recursive=True)
for process in children:
process.send_signal(sig)

Since you appear to be using Unix, you can use a quick ps command to get the details of the child processes, like I did here (this is Linux-specific):
import subprocess, os, signal
def kill_child_processes(parent_pid, sig=signal.SIGTERM):
ps_command = subprocess.Popen("ps -o pid --ppid %d --noheaders" % parent_pid, shell=True, stdout=subprocess.PIPE)
ps_output = ps_command.stdout.read()
retcode = ps_command.wait()
assert retcode == 0, "ps command returned %d" % retcode
for pid_str in ps_output.split("\n")[:-1]:
os.kill(int(pid_str), sig)

For your example you may use the subprocess package. By default it executes the command without shell (like os.system()) and provides a PID:
from subprocess import Popen
p = Popen('iostat 2 > a.txt', shell=True)
processId = p.pid
p.communicate() # to wait until the end
The Popen also provides ability to connect to standard input and output of the process.
note: before using shell=True be aware of the security considerations.

I think with the multiprocess module you might be out of luck since you are really forking python directly and are given that Process object instead of the process you are interested in at the bottom of the process tree.
An alternative way, but perhaps not optimal way, to get that pid is to use the psutil module to look it up using the pid obtained from your Process object. Psutil, however, is system dependent and will need to be installed separately on each of your target platforms.
Note: I'm not currently at a machine I typically work from, so I can't provide working code nor play around to find a better option, but will edit this answer when I can to show how you might be able to do this.

[me#localhost ~]$ echo $$
30399
[me#localhost ~]$ cat iostat.py
#!/usr/bin/env python3.4
import multiprocessing
import os
d = multiprocessing.Process(target=os.system,args=('iostat 2 > a.txt',))
d.start()
[me#localhost ~]$ ./iostat.py &
[1] 31068
[me#localhost ~]$ watch -n 3 'pstree -p 30399'
[me#localhost ~]$
This gave me the PID of iostat See image.