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Simultaneously read stdout and stderr from Python `asyncio` create_subprocess_exec
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| import asyncio | |
| async def run(): | |
| proc = await asyncio.create_subprocess_exec( | |
| '/bin/ls', '/etc', '/not-exists', | |
| stdout=asyncio.subprocess.PIPE, | |
| stderr=asyncio.subprocess.PIPE | |
| ) | |
| # Prepare set of asynchronous readline() tasks for `stdout` and `stderr` streams | |
| aws = { | |
| asyncio.create_task(proc.stdout.readline(), name="stdout"), | |
| asyncio.create_task(proc.stderr.readline(), name="stderr"), | |
| } | |
| while len(aws) > 0: | |
| done, aws = await asyncio.wait(aws, return_when=asyncio.FIRST_COMPLETED) | |
| for task in done: | |
| line = await task | |
| # If the line is empty, we are at the end of the stream | |
| if len(line) == 0: | |
| continue | |
| print(">>", task.get_name(), line) | |
| # Re-create a readline() task for a respective stream | |
| if task.get_name() == "stdout": | |
| aws.add(asyncio.create_task(proc.stdout.readline(), name="stdout")) | |
| elif task.get_name() == "stderr": | |
| aws.add(asyncio.create_task(proc.stderr.readline(), name="stderr")) | |
| # Wait till the process is finished | |
| returncode = await proc.wait() | |
| print('Exited with code', returncode) | |
| asyncio.run(run()) |
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