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112 lines
3.0 KiB
112 lines
3.0 KiB
2 years ago
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from __future__ import print_function
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"""
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Utility class for spawning and controlling CLI processes.
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See: http://stackoverflow.com/questions/375427/non-blocking-read-on-a-subprocess-pipe-in-python
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"""
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import sys, time
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from subprocess import PIPE, Popen
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from threading import Thread
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try:
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from Queue import Queue, Empty
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except ImportError:
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from queue import Queue, Empty # python 3.x
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ON_POSIX = "posix" in sys.builtin_module_names
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class Process(object):
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"""
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Process encapsulates a subprocess with queued stderr/stdout pipes.
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Wraps most methods from subprocess.Popen.
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For non-blocking reads, use proc.stdout.get_nowait() or
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proc.stdout.get(timeout=0.1).
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"""
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def __init__(self, exec_args, cwd=None):
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self.proc = Popen(
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exec_args,
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stdout=PIPE,
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stdin=PIPE,
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stderr=PIPE,
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bufsize=1,
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close_fds=ON_POSIX,
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universal_newlines=True,
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cwd=cwd,
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)
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self.stdin = self.proc.stdin
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# self.stdin = PipePrinter(self.proc.stdin)
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self.stdout = PipeQueue(self.proc.stdout)
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self.stderr = PipeQueue(self.proc.stderr)
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for method in ["poll", "wait", "send_signal", "kill", "terminate"]:
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setattr(self, method, getattr(self.proc, method))
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class PipePrinter(object):
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""" For debugging writes to a pipe.
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"""
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def __init__(self, pipe):
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self._pipe = pipe
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def __getattr__(self, attr):
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return getattr(self._pipe, attr)
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def write(self, strn):
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print("WRITE:" + repr(strn))
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return self._pipe.write(strn)
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class PipeQueue(Queue):
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"""
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Queue that starts a second process to monitor a PIPE for new data.
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This is needed to allow non-blocking pipe reads.
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"""
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def __init__(self, pipe):
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Queue.__init__(self)
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self.thread = Thread(target=self.enqueue_output, args=(pipe, self))
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self.thread.daemon = True # thread dies with the program
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self.thread.start()
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@staticmethod
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def enqueue_output(out, queue):
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for line in iter(out.readline, b""):
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queue.put(line)
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# print "READ: " + repr(line)
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out.close()
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def read(self):
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"""
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Read all available lines from the queue, concatenated into a single string.
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"""
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out = ""
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while True:
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try:
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out += self.get_nowait()
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except Empty:
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break
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return out
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def readline(self, timeout=None):
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""" Read a single line from the queue.
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"""
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# we break this up into multiple short reads to allow keyboard
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# interrupts
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start = time.time()
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ret = ""
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while True:
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if timeout is not None:
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remaining = start + timeout - time.time()
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if remaining <= 0:
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return ""
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else:
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remaining = 1
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try:
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return self.get(timeout=min(0.1, remaining))
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except Empty:
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pass
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