Fix #444582. Add shutil.which function for finding programs on the system path.

This commit is contained in:
Brian Curtin 2012-06-22 16:00:30 -05:00
parent ebd1b1dcb7
commit c57a34577c
4 changed files with 121 additions and 2 deletions

View file

@ -36,7 +36,7 @@ __all__ = ["copyfileobj", "copyfile", "copymode", "copystat", "copy", "copy2",
"register_archive_format", "unregister_archive_format",
"get_unpack_formats", "register_unpack_format",
"unregister_unpack_format", "unpack_archive",
"ignore_patterns", "chown"]
"ignore_patterns", "chown", "which"]
# disk_usage is added later, if available on the platform
class Error(EnvironmentError):
@ -961,3 +961,51 @@ def get_terminal_size(fallback=(80, 24)):
lines = size.lines
return os.terminal_size((columns, lines))
def which(cmd, mode=os.F_OK | os.X_OK, path=None):
"""Given a file, mode, and a path string, return the path whichs conform
to the given mode on the path."""
# 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):
if (os.path.exists(fn) and os.access(fn, mode)
and not os.path.isdir(fn)):
return True
return False
# Short circuit. If we're given a full path which matches the mode
# and it exists, we're done here.
if _access_check(cmd, mode):
return cmd
path = (path or os.environ.get("PATH", os.defpath)).split(os.pathsep)
if sys.platform == "win32":
# The current directory takes precedence on Windows.
if not os.curdir 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".
matches = [cmd for ext in pathext if cmd.lower().endswith(ext.lower())]
# If it does match, only test that one, otherwise we have to try others.
files = [cmd + ext.lower() for ext in pathext] if not matches else [cmd]
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:
dir = os.path.normcase(os.path.abspath(dir))
if not dir in seen:
seen.add(dir)
for thefile in files:
name = os.path.join(dir, thefile)
if _access_check(name, mode):
return name
return None