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@turingbirds turingbirds/invoke.py
Last active Aug 29, 2015

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Execute a child program in a new process
#!/usr/bin/python
# -*- coding: utf-8 -*-
"""Execute a child program in a new process"""
import os
import subprocess
def exec_binary(cmd_line_list, cwd=None, stdout=None, stderr=None, verbose=False):
"""Invoke an executable file.
Example
-------
Easy:
>>> exec_binary('ls', verbose=True)
Pass parameters:
>>> cmd_line_list = [os.path.join('mypathtobin', 'mybin.exe'), '-conf', myparameter]
>>> if verbose:
>>> cmd_line_list += ['-v']
>>> exec_binary(cmd_line_list, verbose=verbose)
Capturing stdout:
>>> import tempfile
>>> [out_fd, out_fname] = tempfile.mkstemp()
>>> try:
>>> exec_binary(cmd_line_list, cwd=bindir, stderr=out_fd, verbose=False)
>>> finally:
>>> os.fsync(out_fd)
>>> os.lseek(out_fd, 0, os.SEEK_SET)
>>> out = os.read(out_fd, 100) # captures stdout
>>> os.close(out_fd)
>>> cleanup_files([out_fname])
Parameters
----------
cmd_line_list : list
Passed as first argument to subprocess.Popen.
cwd : string
If not ``None``, change current directory to ``cwd``. Old cwd will be
restored after exit.
stdout : None or open, writeable file stream
If provided, redirect stdout to the given file stream.
stderr : None or open, writeable file stream
If provided, redirect stderr to the given file stream.
verbose : boolean
If False, redirect tool stdout and stderr to /dev/null, unless stdout
parameter is given.
"""
if verbose:
print '* Invoking external tool...'
print ' Command line is: ' + ' '.join(cmd_line_list)
# set cwd
if cwd != None:
old_cwd = os.getcwd()
os.chdir(cwd)
try:
if not verbose:
devnull = open('/dev/null','w')
if stdout == None:
stdout = devnull
if stderr == None:
stderr = devnull
try:
# invoke the tool
proc = subprocess.Popen(cmd_line_list, stdout=stdout, stderr=stderr)
proc.wait()
finally:
if not verbose:
devnull.close()
if proc.returncode > 0:
raise Exception('Error executing external tool! Return code ' + str(proc.returncode))
finally:
# restore old cwd
if cwd != None:
os.chdir(old_cwd)
def cleanup_files(fname_list, verbose=False):
for fname in fname_list:
if verbose:
print '* Removing file \'' + fname + '\''
try:
os.remove(fname)
except:
print '/!\ Warning: could not remove file ' + fname
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