Python forked processes won't die

Question

I've seen several questions like this one, but after trying various variants of checking if the children are alive and exiting the children processes, I simplified the problem and still it will not work. Am I wrong in exiting a forked process with sys.exit(0)? Is there another way to kill it. The thing is, I cannot have the parent kill the processes since it won't know when they're done working. At first I thought it was because a executed a system command before exiting (Python run system command and then exit... won't exit), but I've even removed that in the simplified version as given solution didn't work either. Here's an example: ``` import sys import os import time children = [] for i in range(0,3): pid = os.fork() if pid == -1: continue elif pid == 0: # Do work... print 'Child %d spawned' % os.getpid() sys.exit(0) else: children.append(pid) time.sleep(5) for pid in children: proc_path = '/proc/%d' % pid if not os.path.exists(proc_path): print 'Child %d is dead' % pid else: prin…

Accepted Answer

You have to `wait()` for the child-process.

Please add the following lines to get things corrected:

```
import sys
import os
import time

children = []

for i in range(0,3):    
    pid = os.fork()

if pid == -1:
        continue
    elif pid == 0:
        # Do work...
        print 'Child %d spawned' % os.getpid()
        sys.exit(0)     
    else:
        children.append(pid)

time.sleep(5)

# ADD NEXT TWO LINES:
for pid in children:
    os.waitpid(pid, 0)

for pid in children:
    proc_path = '/proc/%d' % pid
    if not os.path.exists(proc_path):
        print 'Child %d is dead' % pid
    else:
        print 'Child %d is alive' % pid
```

The parent must `wait()` for the child. Please see `man 2 wait`for details.

In python you can handle those things with the `subprocess` module.

Python forked processes won't die

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