Cross-platform/cross-python shutil.which functionality.
# -*- coding: utf-8 -*- __author__ = "Daniel Roy Greenfeld" __email__ = "email@example.com" __version__ = "0.5.3" import os import sys try: # Forced testing from shutil import which except ImportError: # Forced testing # Versions prior to Python 3.3 don't have shutil.which def which(cmd, mode=os.F_OK | os.X_OK, path=None): """Given a command, mode, and a PATH string, return the path which conforms to the given mode on the PATH, or None if there is no such file. `mode` defaults to os.F_OK | os.X_OK. `path` defaults to the result of os.environ.get("PATH"), or can be overridden with a custom search path. Note: This function was backported from the Python 3 source code. """ # Check that a given file can be accessed with the correct mode. # Additionally check that `file` is not a directory, as on Windows # directories pass the os.access check. def _access_check(fn, mode): return os.path.exists(fn) and os.access(fn, mode) and not os.path.isdir(fn) # If we're given a path with a directory part, look it up directly # rather than referring to PATH directories. This includes checking # relative to the current directory, e.g. ./script if os.path.dirname(cmd): if _access_check(cmd, mode): return cmd return None if path is None: path = os.environ.get("PATH", os.defpath) if not path: return None path = path.split(os.pathsep) if sys.platform == "win32": # The current directory takes precedence on Windows. if os.curdir not in path: path.insert(0, os.curdir) # PATHEXT is necessary to check on Windows. pathext = os.environ.get("PATHEXT", "").split(os.pathsep) # See if the given file matches any of the expected path # extensions. This will allow us to short circuit when given # "python.exe". If it does match, only test that one, otherwise we # have to try others. if any(cmd.lower().endswith(ext.lower()) for ext in pathext): files = [cmd] else: files = [cmd + ext for ext in pathext] else: # On other platforms you don't have things like PATHEXT to tell you # what file suffixes are executable, so just pass on cmd as-is. files = [cmd] seen = set() for dir in path: normdir = os.path.normcase(dir) if normdir not in seen: seen.add(normdir) for thefile in files: name = os.path.join(dir, thefile) if _access_check(name, mode): return name return None