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Writing to sys.stdout on OS X can fail with IOError: [Errno 4] Interrupted system call.
I have observed this while trying to write to sys.stdout when SIGCHLD is received. The script below consistently reproduces the problem with python 2.7.2 on OS X 10.9.3.
import sys
import os
import signal
import subprocess
import time
children = {}
def claim_child():
 pid, status = os.wait()
 p = children.pop(pid)
def trap(sig, frame):
 claim_child()
signal.signal(signal.SIGCHLD, trap)
running = 0
max_procs = 70
program = [sys.executable, '-c', 'import sys, time; print sys.version; time.sleep(3)']
f = sys.stdout # crashes with: IOError: [Errno 4] Interrupted system call
# f = file('/tmp/eintr.log', 'w') # works just fine
while True:
 while len(children) < max_procs:
 f.write('starting program: {}\n'.format(program))
 p = subprocess.Popen(program)
 children[p.pid] = p
 time.sleep(0.05)