utils.py 文件源码

def fork_exec(cmd,
              exec_env=None,
              logfile=None,
              pass_fds=None):
    """Execute a command using fork/exec.

    This is needed for programs system executions that need path
    searching but cannot have a shell as their parent process, for
    example: glare.  When glare starts it sets itself as
    the parent process for its own process group.  Thus the pid that
    a Popen process would have is not the right pid to use for killing
    the process group.  This patch gives the test env direct access
    to the actual pid.

    :param cmd: Command to execute as an array of arguments.
    :param exec_env: A dictionary representing the environment with
                     which to run the command.
    :param logfile: A path to a file which will hold the stdout/err of
                   the child process.
    :param pass_fds: Sequence of file descriptors passed to the child.
    """
    env = os.environ.copy()
    if exec_env is not None:
        for env_name, env_val in exec_env.items():
            if callable(env_val):
                env[env_name] = env_val(env.get(env_name))
            else:
                env[env_name] = env_val

    pid = os.fork()
    if pid == 0:
        if logfile:
            fds = [1, 2]
            with open(logfile, 'r+b') as fptr:
                for desc in fds:  # close fds
                    try:
                        os.dup2(fptr.fileno(), desc)
                    except OSError:
                        pass
        if pass_fds and hasattr(os, 'set_inheritable'):
            # os.set_inheritable() is only available and needed
            # since Python 3.4. On Python 3.3 and older, file descriptors are
            # inheritable by default.
            for fd in pass_fds:
                os.set_inheritable(fd, True)

        args = shlex.split(cmd)
        os.execvpe(args[0], args, env)
    else:
        return pid