In python 2.7 in windows according to the documentation you can send a CTRL_C_EVENT (Python 2.7 Subprocess Popen.send_signal documentation). However when I tried it I did not receive the expected keyboard interrupt in the subprocess.
This is the sample code for for the parent process:
# FILE : parentProcess.py
import subprocess
import time
import signal
CREATE_NEW_PROCESS_GROUP = 512
process = subprocess.Popen(['python', '-u', 'childProcess.py'],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
universal_newlines=True,
creationflags=CREATE_NEW_PROCESS_GROUP)
print "pid = ", process.pid
index = 0
maxLoops = 15
while index < maxLoops:
index += 1
# Send one message every 0.5 seconds
time.sleep(0.5)
# Send data to the subprocess
process.stdin.write('Bar\n')
# Read data from the subprocess
temp = process.stdout.readline()
print temp,
if (index == 10):
# Send Keyboard Interrupt
process.send_signal(signal.CTRL_C_EVENT)
This is the sample code for the child proceess:
# FILE : childProcess.py
import sys
while True:
try:
# Get data from main process
temp = sys.stdin.readline()
# Write data out
print 'Foo ' + temp,
except KeyboardInterrupt:
print "KeyboardInterrupt"
If I run the file parentProcess.py I expect to get "Foo Bar" ten times then a "KeyboardInterrupt" followed by "Foo Bar" 4 times but I get "Foo Bar" 15 times instead.
Is there a way to get the CTRL_C_EVENT to behave as a keyboard interrupt just as SIGINT behaves in Linux?
After doing some reading I found some information that seems to contradic the python documentation regarding CTRL_C_EVENT, in particular it says that
CTRL_C_EVENT 0 Generates a CTRL+C signal. This signal cannot be generated for process groups
The following site provide more inforamtion about creation flags: Process Creation Flags.
This method of signal handling by subprocesses worked for me on both Linux and Windows 2008, both using Python 2.7.2, but it uses Ctrl-Break instead of Ctrl-C. See the note about process groups and Ctrl-C in http://msdn.microsoft.com/en-us/library/ms683155%28v=vs.85%29.aspx.
catcher.py:
import os
import signal
import sys
import time
def signal_handler(signal, frame):
print 'catcher: signal %d received!' % signal
raise Exception('catcher: i am done')
if hasattr(os.sys, 'winver'):
signal.signal(signal.SIGBREAK, signal_handler)
else:
signal.signal(signal.SIGTERM, signal_handler)
print 'catcher: started'
try:
while(True):
print 'catcher: sleeping...'
time.sleep(1)
except Exception as ex:
print ex
sys.exit(0)
thrower.py:
import signal
import subprocess
import time
import os
args = [
'python',
'catcher.py',
]
print 'thrower: starting catcher'
if hasattr(os.sys, 'winver'):
process = subprocess.Popen(args, creationflags=subprocess.CREATE_NEW_PROCESS_GROUP)
else:
process = subprocess.Popen(args)
print 'thrower: waiting a couple of seconds for catcher to start...'
time.sleep(2)
print 'thrower: sending signal to catch'
if hasattr(os.sys, 'winver'):
os.kill(process.pid, signal.CTRL_BREAK_EVENT)
else:
process.send_signal(signal.SIGTERM)
print 'thrower: i am done'