cpython/Lib/os.py

# os.py -- either mac, dos or posix depending on what system we're on.

# This exports:
# - all functions from either posix or mac, e.g., os.unlink, os.stat, etc.
# - os.path is either module posixpath or macpath
# - os.name is either 'posix' or 'mac'
# - os.curdir is a string representing the current directory ('.' or ':')
# - os.pardir is a string representing the parent directory ('..' or '::')
# - os.sep is the (or a most common) pathname separator ('/' or ':')

# Programs that import and use 'os' stand a better chance of being
# portable between different platforms.  Of course, they must then
# only use functions that are defined by all platforms (e.g., unlink
# and opendir), and leave all pathname manipulation to os.path
# (e.g., split and join).

# XXX This is incorrect if the import *path fails...

try:
	from posix import *
	try:
		from posix import _exit
	except ImportError:
		pass
	name = 'posix'
	curdir = '.'
	pardir = '..'
	sep = '/'
	import posixpath
	path = posixpath
	del posixpath
except ImportError:
	try:
		from mac import *
		name = 'mac'
		curdir = ':'
		pardir = '::'
		sep = ':'
		import macpath
		path = macpath
		del macpath
	except ImportError:
		from dos import *
		name = 'dos'
		curdir = '.'		# XXX doesn't always work
		pardir = '..'		# XXX doesn't always work
		sep = '/'		# XXX or '\\' ???
		import dospath
		path = dospath
		del dospath

def execl(file, *args):
	execv(file, args)

def execle(file, *args):
	env = args[-1]
	execve(file, args[:-1], env)

def execlp(file, *args):
	execvp(file, args)

def execvp(file, args):
	if '/' in file:
		execv(file, args)
		return
	ENOENT = 2
	if environ.has_key('PATH'):
		import string
		PATH = string.splitfields(environ['PATH'], ':')
	else:
		PATH = ['', '/bin', '/usr/bin']
	exc, arg = (ENOENT, 'No such file or directory')
	for dir in PATH:
		fullname = path.join(dir, file)
		try:
			execv(fullname, args)
		except error, (errno, msg):
			if errno != ENOENT:
				exc, arg = error, (errno, msg)
	raise exc, arg