Python os 模块，fchdir() 实例源码

def __enter__(self):
        self.mount()
        os.chroot(self.chroot)
        os.fchdir(self.chroot_fd)
        return self

def __exit__(self, exc_type, exc_val, exc_tb):
        os.fchdir(self.orig_fd)
        os.chroot(".")
        os.close(self.orig_fd)
        os.close(self.chroot_fd)
        self.umount()

def executeCommand(command):
    cwd = os.getcwd()
    rr = os.open("/", os.O_RDONLY)
    os.chroot(getRootDir.getEnvsDir() + getEnvName())
    os.chdir("/")
    os.system(command)
    os.fchdir(rr)
    os.chroot(".")
    os.chdir(cwd)

def execute_git(state, repo_git, args, capture=False, capture_stderr=False):
    """Executes a Git command in the given repository, with args being a list
    of arguments (not including git itself). capture and capture_stderr
    arguments causes it to return stdout or stdout+stderr as a string.

    state can be None, but if so, then repo_git needs to be an absolute path.

    The function automatically takes into account Git commands with side effects
    and applies push simulation and dry run if those are enabled."""

    is_push = (args[0] == "push")
    is_change = (is_push
                 or (args[0] == "tag" and len(args) > 1)
                 or (args[0] == "branch" and len(args) > 1)
                 or (args[0] == "config" and args[1] != "-l")
                 or (args[0] == "checkout")
                 or (args[0] == "commit")
                 or (args[0] == "fetch")
                 or (args[0] == "init")
                 or (args[0] == "reset"))

    if os.path.isabs(repo_git):
        git_dir = repo_git
    else:
        git_dir = os.path.join(state['repo_dir'], repo_git)

    if (not PUSH and is_push) or (DRY_RUN and is_change):
        print("Would have executed: cd %s && git %s"
              % (git_dir, " ".join(args)))
        return None

    fd = os.open(".", flags=os.O_RDONLY)
    os.chdir(git_dir)
    if capture_stderr:
        stderr = subprocess.STDOUT
    else:
        stderr = None

    try:
        if capture:
            output = subprocess.check_output(["git"] + args, stderr=stderr).decode().strip()
        else:
            output = None
            subprocess.check_call(["git"] + args, stderr=stderr)
    finally:
        os.fchdir(fd)
        os.close(fd)

    return output