"""
Helper functions for interacting with the shell, and consuming shell-style
parameters provided in config files.
"""
import os
import shlex
import subprocess
try:
from shlex import quote
except ImportError:
from pipes import quote
__all__ = ['WindowsParser', 'PosixParser', 'NativeParser']
class CommandLineParser:
"""
An object that knows how to split and join command-line arguments.
It must be true that ``argv == split(join(argv))`` for all ``argv``.
The reverse neednt be true - `join(split(cmd))` may result in the addition
or removal of unnecessary escaping.
"""
@staticmethod
def join(argv):
""" Join a list of arguments into a command line string """
raise NotImplementedError
@staticmethod
def split(cmd):
""" Split a command line string into a list of arguments """
raise NotImplementedError
class WindowsParser:
"""
The parsing behavior used by `subprocess.call("string")` on Windows, which
matches the Microsoft C/C++ runtime.
Note that this is _not_ the behavior of cmd.
"""
@staticmethod
def join(argv):
# note that list2cmdline is specific to the windows syntax
return subprocess.list2cmdline(argv)
@staticmethod
def split(cmd):
import ctypes # guarded import for systems without ctypes
try:
ctypes.windll
except AttributeError:
raise NotImplementedError
# Windows has special parsing rules for the executable (no quotes),
# that we do not care about - insert a dummy element
if not cmd:
return []
cmd = 'dummy ' + cmd
CommandLineToArgvW = ctypes.windll.shell32.CommandLineToArgvW
CommandLineToArgvW.restype = ctypes.POINTER(ctypes.c_wchar_p)
CommandLineToArgvW.argtypes = (ctypes.c_wchar_p, ctypes.POINTER(ctypes.c_int))
nargs = ctypes.c_int()
lpargs = CommandLineToArgvW(cmd, ctypes.byref(nargs))
args = [lpargs[i] for i in range(nargs.value)]
assert not ctypes.windll.kernel32.LocalFree(lpargs)
# strip the element we inserted
assert args[0] == "dummy"
return args[1:]
class PosixParser:
"""
The parsing behavior used by `subprocess.call("string", shell=True)` on Posix.
"""
@staticmethod
def join(argv):
return ' '.join(quote(arg) for arg in argv)
@staticmethod
def split(cmd):
return shlex.split(cmd, posix=True)
if os.name == 'nt':
NativeParser = WindowsParser
elif os.name == 'posix':
NativeParser = PosixParser
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