<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def shebang(self, line, cell):
 """Run a cell via a shell command The `%%script` line is like the #! line of script, specifying a program (bash, perl, ruby, etc.) with which to run. The rest of the cell is run by that program. Examples -------- :: In [1]: %%script bash 1 2 3 """

        argv = arg_split(line, posix=not sys.platform.startswith('win'))
        args, cmd = self.shebang.parser.parse_known_args(argv)

        try:
            p = Popen(cmd, stdout=PIPE, stderr=PIPE, stdin=PIPE)
        except OSError as e:
            if e.errno == errno.ENOENT:
                print("Couldn't find program: %r" % cmd[0])
                return
            else:
                raise

        if not cell.endswith('\n'):
            cell += '\n'
        cell = cell.encode('utf8', 'replace')
        if args.bg:
            self.bg_processes.append(p)
            self._gc_bg_processes()
            if args.out:
                self.shell.user_ns[args.out] = p.stdout
            if args.err:
                self.shell.user_ns[args.err] = p.stderr
            self.job_manager.new(self._run_script, p, cell, daemon=True)
            if args.proc:
                self.shell.user_ns[args.proc] = p
            return

        try:
            out, err = p.communicate(cell)
        except KeyboardInterrupt:
            try:
                p.send_signal(signal.SIGINT)
                time.sleep(0.1)
                if p.poll() is not None:
                    print("Process is interrupted.")
                    return
                p.terminate()
                time.sleep(0.1)
                if p.poll() is not None:
                    print("Process is terminated.")
                    return
                p.kill()
                print("Process is killed.")
            except OSError:
                pass
            except Exception as e:
                print("Error while terminating subprocess (pid=%i): %s" \
                      % (p.pid, e))
            return
        out = py3compat.bytes_to_str(out)
        err = py3compat.bytes_to_str(err)
        if args.out:
            self.shell.user_ns[args.out] = out
        else:
            sys.stdout.write(out)
            sys.stdout.flush()
        if args.err:
            self.shell.user_ns[args.err] = err
        else:
            sys.stderr.write(err)
            sys.stderr.flush()