proxy.py 文件源码

def spawn(self, argv=None):
        '''
        Create a spawned process.
        Based on the code for pty.spawn().
        '''
        assert self.master_fd is None

        pid, master_fd = pty.fork()
        self.master_fd = master_fd
        self.pid = pid
        if pid == pty.CHILD:
            if self.user is not None:
                try:
                    uid = pwd.getpwnam(self.user).pw_uid
                except KeyError:
                    log.error("No such user: %s", self.user)
                else:
                    os.setuid(uid)
                    log.debug('switched user for remote process to %s(%s)', self.user, uid)
            if self.group is not None:
                try:
                    gid = grp.getgrnam(self.group).gr_gid
                except KeyError:
                    log.error("No such group: %s", self.group)
                else:
                    os.setgid(gid)
                    log.debug('switched group for remote process to %s(%s)', self.group, gid)
            if not argv:
                argv = [os.environ['SHELL']]
            os.execlp(argv[0], *argv)
            # Previous command replaces the process
            return

        self._init_fd()
        try:
            self._copy()
        except (IOError, OSError):
            pass

        os.close(master_fd)
        self.master_fd = None