使用 gnu clisp 运行 shell 命令

我正在尝试为 clisp 创建一个“系统”命令，其工作原理如下

(setq result (system "pwd"))

;;now result is equal to /my/path/here

我有这样的事情：

(defun system (cmd)
 (ext:run-program :output :stream))

但是，我不确定如何将流转换为字符串。我已经多次查看了 hyperspec 和 google。

编辑：使用 Ranier 的命令并使用 with-output-to-stream，

(defun system (cmd)
  (with-output-to-string (stream)
    (ext:run-program cmd :output stream)))

然后尝试运行grep，这是我的道路...

[11]> (system "grep")

*** - STRING: argument #<OUTPUT STRING-OUTPUT-STREAM> should be a string, a
      symbol or a character
The following restarts are available:
USE-VALUE      :R1      Input a value to be used instead.
ABORT          :R2      Abort main loop
Break 1 [12]> :r2

像这样的东西吗？

版本2：

(defun copy-stream (in out)
   (loop for line = (read-line in nil nil)
         while line
         do (write-line line out)))

(defun system (cmd)
  (with-open-stream (s1 (ext:run-program cmd :output :stream))
    (with-output-to-string (out)
      (copy-stream s1 out))))


[6]> (system "ls")
"#.emacs#
Applications
..."