Example of ulimiting some forks

0_shell.sh

$ /bin/bash ulimiter.sh 40 forks.py
0: 9388
2: 9390
1: 9389
3: 9391
4: 9392
6: 9394
5: 9393
7: 9395
8: 9396
9: 9397
10: 9398
11: 9399
12: 9400
13: 9401
14: 9402
15: 9403
16: 9404
17: 9405
18: 9406
19: 9407
20: 9408
21: 9409
22: 9410
23: 9411
24: 9412
25: 9413
26: 9414
27: 9415
Traceback (most recent call last):
  File "tmp.py", line 13, in <module>
    raise e
OSError: [Errno 11] Resource temporarily unavailable
$

1_ulimiter.sh

#! /usr/bin/env bash
if [ ! -z ${1} ]; then
    ulimit -Su $1
    ulimit -Hu $1
fi
python=`which python`
$python $2 $1

2_forks.py

#! /usr/bin/env python
import os, sys, time
n = int(sys.argv[1])
for i in range(0, n):
    try:
        pid = os.fork()
        if pid == 0:
            continue
        print "{}: {}".format(i, pid)
        break
    except OSError as e:
        if e.errno == 11:
            raise e
time.sleep(4)