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Running a command in Python and optionally processing the output in realtime.
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| import shlex | |
| import subprocess | |
| import sys | |
| def run_cmd(cmd, callback=None, watch=False): | |
| """Runs the given command and gathers the output. | |
| If a callback is provided, then the output is sent to it, otherwise it | |
| is just returned. | |
| Optionally, the output of the command can be "watched" and whenever new | |
| output is detected, it will be sent to the given `callback`. | |
| Args: | |
| cmd (str): The command to run. | |
| Kwargs: | |
| callback (func): The callback to send the output to. | |
| watch (bool): Whether to watch the output of the command. If True, | |
| then `callback` is required. | |
| Returns: | |
| A string containing the output of the command, or None if a `callback` | |
| was given. | |
| Raises: | |
| RuntimeError: When `watch` is True, but no callback is given. | |
| """ | |
| if watch and not callback: | |
| raise RuntimeError('You must provide a callback when watching a process.') | |
| output = None | |
| try: | |
| proc = subprocess.Popen(shlex.split(cmd), stdout=subprocess.PIPE) | |
| if watch: | |
| while proc.poll() is None: | |
| line = proc.stdout.readline() | |
| if line != "": | |
| callback(line) | |
| # Sometimes the process exits before we have all of the output, so | |
| # we need to gather the remainder of the output. | |
| remainder = proc.communicate()[0] | |
| if remainder: | |
| callback(remainder) | |
| else: | |
| output = proc.communicate()[0] | |
| except: | |
| err = str(sys.exc_info()[1]) + "\n" | |
| output = err | |
| if callback and output is not None: | |
| callback(output) | |
| return None | |
| return output |
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| import sys | |
| from cmd import run_cmd | |
| print run_cmd("ls -al") | |
| def flush(message): | |
| sys.stdout.write(message) | |
| sys.stdout.flush() | |
| run_cmd("ping google.com", callback=flush, watch=True) |
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