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"""Example writing to and reading from a subprocess at the same time using
tasks."""
import asyncio
import os
from asyncio.subprocess import PIPE
@asyncio.coroutine
def send_input(writer, input):
try:
for line in input:
print('sending', len(line), 'bytes')
writer.write(line)
d = writer.drain()
if d:
print('pause writing')
yield from d
print('resume writing')
writer.close()
except BrokenPipeError:
print('stdin: broken pipe error')
except ConnectionResetError:
print('stdin: connection reset error')
@asyncio.coroutine
def log_errors(reader):
while True:
line = yield from reader.readline()
if not line:
break
print('ERROR', repr(line))
@asyncio.coroutine
def read_stdout(stdout):
while True:
line = yield from stdout.readline()
print('received', repr(line))
if not line:
break
@asyncio.coroutine
def start(cmd, input=None, **kwds):
kwds['stdout'] = PIPE
kwds['stderr'] = PIPE
if input is None and 'stdin' not in kwds:
kwds['stdin'] = None
else:
kwds['stdin'] = PIPE
proc = yield from asyncio.create_subprocess_shell(cmd, **kwds)
tasks = []
if input is not None:
tasks.append(send_input(proc.stdin, input))
else:
print('No stdin')
if proc.stderr is not None:
tasks.append(log_errors(proc.stderr))
else:
print('No stderr')
if proc.stdout is not None:
tasks.append(read_stdout(proc.stdout))
else:
print('No stdout')
if tasks:
# feed stdin while consuming stdout to avoid hang
# when stdin pipe is full
yield from asyncio.wait(tasks)
exitcode = yield from proc.wait()
print("exit code: %s" % exitcode)
def main():
if os.name == 'nt':
loop = asyncio.ProactorEventLoop()
asyncio.set_event_loop(loop)
else:
loop = asyncio.get_event_loop()
loop.run_until_complete(start(
'sleep 2; wc', input=[b'foo bar baz\n'*300 for i in range(100)]))
loop.close()
if __name__ == '__main__':
main()
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