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 ':' or '\\')
# - os.altsep is the alternatte pathname separator (None or '/')
# - os.pathsep is the component separator used in $PATH etc
# - os.defpath is the default search path for executables

# 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).

import sys

_names = sys.builtin_module_names

altsep = None

if 'posix' in _names:
    name = 'posix'
    linesep = '\n'
    curdir = '.'; pardir = '..'; sep = '/'; pathsep = ':'
    defpath = ':/bin:/usr/bin'
    from posix import *
    try:
        from posix import _exit
    except ImportError:
        pass
    import posixpath
    path = posixpath
    del posixpath
elif 'nt' in _names:
    name = 'nt'
    linesep = '\r\n'
    curdir = '.'; pardir = '..'; sep = '\\'; pathsep = ';'
    defpath = '.;C:\\bin'
    from nt import *
    try:
        from nt import _exit
    except ImportError:
        pass
    import ntpath
    path = ntpath
    del ntpath
elif 'dos' in _names:
    name = 'dos'
    linesep = '\r\n'
    curdir = '.'; pardir = '..'; sep = '\\'; pathsep = ';'
    defpath = '.;C:\\bin'
    from dos import *
    try:
        from dos import _exit
    except ImportError:
        pass
    import dospath
    path = dospath
    del dospath
elif 'os2' in _names:
    name = 'os2'
    linesep = '\r\n'
    curdir = '.'; pardir = '..'; sep = '\\'; pathsep = ';'
    defpath = '.;C:\\bin'
    from os2 import *
    try:
        from os2 import _exit
    except ImportError:
        pass
    import ntpath
    path = ntpath
    del ntpath
elif 'mac' in _names:
    name = 'mac'
    linesep = '\r'
    curdir = ':'; pardir = '::'; sep = ':'; pathsep = '\n'
    defpath = ':'
    from mac import *
    try:
        from mac import _exit
    except ImportError:
        pass
    import macpath
    path = macpath
    del macpath
else:
    raise ImportError, 'no os specific module found'

del _names

# Make sure os.environ exists, at least
try:
    environ
except NameError:
    environ = {}

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 execlpe(file, *args):
    env = args[-1]
    execvpe(file, args[:-1], env)

def execvp(file, args):
    _execvpe(file, args)

def execvpe(file, args, env):
    _execvpe(file, args, env)

_notfound = None
def _execvpe(file, args, env = None):
    if env:
        func = execve
        argrest = (args, env)
    else:
        func = execv
        argrest = (args,)
        env = environ
    global _notfound
    head, tail = path.split(file)
    if head:
        apply(func, (file,) + argrest)
        return
    if env.has_key('PATH'):
        envpath = env['PATH']
    else:
        envpath = defpath
    import string
    PATH = string.splitfields(envpath, pathsep)
    if not _notfound:
        import tempfile
        # Exec a file that is guaranteed not to exist
        try: execv(tempfile.mktemp(), ())
        except error, _notfound: pass
    exc, arg = error, _notfound
    for dir in PATH:
        fullname = path.join(dir, file)
        try:
            apply(func, (fullname,) + argrest)
        except error, (errno, msg):
            if errno != arg[0]:
                exc, arg = error, (errno, msg)
    raise exc, arg

# Change environ to automatically call putenv() if it exists
try:
    # This will fail if there's no putenv
    putenv
except NameError:
    pass
else:
    import UserDict

    if name in ('os2', ):  # Where Env Var Names Must Be UPPERCASE
        import string
        class _Environ(UserDict.UserDict):
            def __init__(self, environ):
                UserDict.UserDict.__init__(self)
                self.data = environ
            def __setitem__(self, key, item):
                key = string.upper(key)
                putenv(key, item)
                self.data[key] = item
            def __getitem__(self, key):
                return self.data[string.upper(key)]

    else:  # Where Env Var Names Can Be Mixed Case
        class _Environ(UserDict.UserDict):
            def __init__(self, environ):
                UserDict.UserDict.__init__(self)
                self.data = environ
            def __getinitargs__(self):
                import copy
                return (copy.copy(self.data),)
            def __setitem__(self, key, item):
                putenv(key, item)
                self.data[key] = item
            def __copy__(self):
                return _Environ(self.data.copy())

    environ = _Environ(environ)