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import sysv_ipc
import time
import sys
import random
# The parent passes the semaphore's name to me.
key = sys.argv[1]
sem = sysv_ipc.Semaphore(int(key))
print('Child: waiting to aquire semaphore ' + key)
with sem:
print('Child: semaphore {} aquired; holding for 3 seconds.'.format(sem.key))
# Flip a coin to determine whether or not to bail out of the context.
if random.randint(0, 1):
print("Child: raising ValueError to demonstrate unplanned context exit")
raise ValueError
time.sleep(3)
print('Child: gracefully exiting context (releasing the semaphore).')
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