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# R overlay -- tools, subprocess helpers
# -*- coding: utf-8 -*-
# Copyright (C) 2014 André Erdmann <dywi@mailerd.de>
# Distributed under the terms of the GNU General Public License;
# either version 2 of the License, or (at your option) any later version.
import os
import subprocess
import sys
import time
__all__ = [
'get_subproc_devnull',
'subproc_send_term', 'subproc_send_kill',
'stop_subprocess', 'gracefully_stop_subprocess',
'create_subprocess', 'run_subprocess'
]
# python >= 3.3 has ProcessLookupError, use more generic exception otherwise
if sys.hexversion >= 0x3030000:
_ProcessLookupError = ProcessLookupError
else:
_ProcessLookupError = OSError
# python >= 3.3:
if hasattr ( subprocess, 'DEVNULL' ):
def get_subproc_devnull(mode=None):
"""Returns a devnull object suitable
for passing it as stdin/stdout/stderr to subprocess.Popen().
Python 3.3 and later variant: uses subprocess.DEVNULL
arguments:
* mode -- ignored
"""
return subprocess.DEVNULL
else:
def get_subproc_devnull(mode='a+'):
"""Returns a devnull object suitable
for passing it as stdin/stdout/stderr to subprocess.Popen().
Python 3.2 and earlier variant: opens os.devnull
arguments:
* mode -- mode for open(). Defaults to read/append
"""
return open ( os.devnull, mode )
# --
def _proc_catch_lookup_err ( func ):
def wrapped ( proc ):
try:
func ( proc )
except _ProcessLookupError:
return False
return True
return wrapped
@_proc_catch_lookup_err
def subproc_send_term ( proc ):
proc.terminate()
@_proc_catch_lookup_err
def subproc_send_kill ( proc ):
proc.kill()
def stop_subprocess ( proc, kill_timeout_cs=10 ):
"""Terminates or kills a subprocess created by subprocess.Popen().
Sends SIGTERM first and sends SIGKILL if the process is still alive after
the given timeout.
Returns: None
arguments:
* proc -- subprocess
* kill_timeout_cs -- max time to wait after terminate() before sending a
kill signal (in centiseconds). Should be an int.
Defaults to 10 (= 1s).
"""
if not subproc_send_term ( proc ):
return
try:
for k in range ( kill_timeout_cs ):
if proc.poll() is not None:
return
time.sleep ( 0.1 )
except:
subproc_send_kill ( proc )
else:
subproc_send_kill ( proc )
# --- end of stop_subprocess (...) ---
def gracefully_stop_subprocess ( proc, **kill_kwargs ):
try:
if subproc_send_term ( proc ):
proc.communicate()
except:
stop_subprocess ( proc, **kill_kwargs )
raise
def create_subprocess ( cmdv, **kwargs ):
"""subprocess.Popen() wrapper that redirects stdin/stdout/stderr to
devnull or to a pipe if set to False/True.
Returns: subprocess
arguments:
* cmdv --
* **kwargs --
"""
devnull_obj = None
for key in { 'stdin', 'stdout', 'stderr' }:
if key not in kwargs:
pass
elif kwargs [key] is True:
kwargs [key] = subprocess.PIPE
elif kwargs [key] is False:
if devnull_obj is None:
devnull_obj = get_subproc_devnull()
assert devnull_obj is not None
kwargs [key] = devnull_obj
# else don't care
# --
return subprocess.Popen ( cmdv, **kwargs )
# --- end of create_subprocess (...) ---
def run_subprocess ( cmdv, kill_timeout_cs=10, **kwargs ):
"""Calls create_subprocess() and waits for the process to exit.
Catches exceptions and terminates/kills the process in that case
Returns: 2-tuple ( subprocess, output )
arguments:
* cmdv --
* kill_timeout_cs -- time to wait after SIGTERM before sending SIGKILL
(in centiseconds), see stop_subprocess() for details
Defaults to 10.
* **kwargs --
"""
proc = None
try:
proc = create_subprocess ( cmdv, **kwargs )
output = proc.communicate()
except:
if proc is not None:
stop_subprocess ( proc, kill_timeout_cs=kill_timeout_cs )
raise
return ( proc, output )
# --- end of run_subprocess (...) ---
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