__init__.py 文件源码

def is_executable_file(path):
    """Checks that path is an executable regular file (or a symlink to a file).

    This is roughly ``os.path isfile(path) and os.access(path, os.X_OK)``, but
    on some platforms :func:`os.access` gives us the wrong answer, so this
    checks permission bits directly.
    """
    # follow symlinks,
    fpath = os.path.realpath(path)

    # return False for non-files (directories, fifo, etc.)
    if not os.path.isfile(fpath):
        return False

    # On Solaris, etc., "If the process has appropriate privileges, an
    # implementation may indicate success for X_OK even if none of the
    # execute file permission bits are set."
    #
    # For this reason, it is necessary to explicitly check st_mode

    # get file mode using os.stat, and check if `other',
    # that is anybody, may read and execute.
    mode = os.stat(fpath).st_mode
    if mode & stat.S_IROTH and mode & stat.S_IXOTH:
        return True

    # get current user's group ids, and check if `group',
    # when matching ours, may read and execute.
    user_gids = os.getgroups() + [os.getgid()]
    if (os.stat(fpath).st_gid in user_gids and
            mode & stat.S_IRGRP and mode & stat.S_IXGRP):
        return True

    # finally, if file owner matches our effective userid,
    # check if `user', may read and execute.
    user_gids = os.getgroups() + [os.getgid()]
    if (os.stat(fpath).st_uid == os.geteuid() and
            mode & stat.S_IRUSR and mode & stat.S_IXUSR):
        return True

    return False