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Handling the live output stream of a command
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| import logging | |
| from collections import deque | |
| from concurrent.futures import ThreadPoolExecutor | |
| from functools import partial | |
| from subprocess import PIPE, CalledProcessError, CompletedProcess, Popen | |
| def stream_command( | |
| args, | |
| *, | |
| stdout_handler=logging.info, | |
| stderr_handler=logging.error, | |
| check=True, | |
| text=True, | |
| stdout=PIPE, | |
| stderr=PIPE, | |
| **kwargs, | |
| ): | |
| """Mimic subprocess.run, while processing the command output in real time.""" | |
| with ( | |
| Popen(args, text=text, stdout=stdout, stderr=stderr, **kwargs) as process, | |
| ThreadPoolExecutor(2) as pool, # two threads to handle the (live) streams separately | |
| ): | |
| exhaust = partial(deque, maxlen=0) # collections recipe: exhaust an iterable at C-speed | |
| exhaust_async = partial(pool.submit, exhaust) # exhaust non-blocking in a background thread | |
| exhaust_async(stdout_handler(line[:-1]) for line in process.stdout) | |
| exhaust_async(stderr_handler(line[:-1]) for line in process.stderr) | |
| retcode = process.poll() # block until both iterables are exhausted (process finished) | |
| if check and retcode: | |
| raise CalledProcessError(retcode, process.args) | |
| return CompletedProcess(process.args, retcode), retcode) |
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| import logging | |
| from subprocess import PIPE, STDOUT, CalledProcessError, CompletedProcess, Popen | |
| def stream_command( | |
| args, | |
| *, | |
| stdout_handler=logging.info, | |
| check=True, | |
| text=True, | |
| **kwargs, | |
| ): | |
| """Mimic subprocess.run, while processing the command output in real time.""" | |
| with Popen(args, text=text, stdout=PIPE, stderr=STDOUT, **kwargs) as process: | |
| for line in process.stdout: | |
| stdout_handler(line[:-1]) | |
| retcode = process.poll() | |
| if check and retcode: | |
| raise CalledProcessError(retcode, process.args) | |
| return CompletedProcess(process.args, retcode) |
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| stream_command(["echo", "test"]) | |
| # INFO:root:test | |
| stream_command("cat ./nonexist", shell=True, check=False) | |
| # ERROR:root:cat: ./nonexist: No such file or directory | |
| stream_command(["echo", "test"], stdout_handler=print) | |
| # test | |
| stdout_lines = [] | |
| def handler(line): | |
| print(line) | |
| logging.info(line) | |
| stdout_lines.append(line) | |
| stream_command(["echo", "test"], stdout_handler=handler) | |
| # test | |
| # INFO:root:test | |
| print(stdout_lines) | |
| # ['test'] | |
| # stream to log file | |
| logging.basicConfig( | |
| level=logging.DEBUG, | |
| format="%(asctime)s:%(levelname)-7s %(filename)20s:%(lineno)-4d %(name)s:%(message)s", | |
| filename="./capture.log", | |
| filemode="w", | |
| encoding="utf-8", | |
| ) | |
| logging.info("test from python") | |
| stream_command(["echo", "test from subprocess"]) |
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