为什么在使用 lein run 按下 ENTER(似乎挂起)后 read-line 没有返回，但可以与 lein repl 一起使用? [英] Why does read-line not return after hitting ENTER (seems like a hang) using lein run, but works with lein repl?

问题描述

手头的问题是，当我用 lein run 运行我的程序时，它进入了 (read-line) 部分，我无法摆脱它，意思是:读行永远不会返回.

The problem at hand is that when I run my program with lein run it gets to the (read-line) part and I can't get out of it, meaning: read-line never returns.

相关代码如下:

(def command (atom ""))

(defn print-prompt []
  (print "prompt> ")
  (flush)
)

(defn ask-for-input []
    (print-prompt)
    (let [x (str (read-line))]
      (println (str "User input: " x))
      (reset! command x)
    )
)

我从未在屏幕上看到用户输入:"字符串.奇怪的是，如果我运行 lein repl 并调用 (ask-for-input) 然后它可以正常工作:S

I never see the "User input: " string on screen. The strange part is, if I run lein repl and call (ask-for-input) then it works correctly :S

推荐答案

试试 lein trampoline run，它有效.

以下内容来自 leiningen 常见问题解答:

The following is from leiningen FAQ:

问:我无法访问我的项目中的 stdin.

Q: I don't have access to stdin inside my project.

A:这是JVM的进程处理方法的限制；他们都没有正确公开标准输入.这意味着像 read-line 这样的函数在大多数情况下不会按预期工作，尽管 repl 任务必须包含一个解决方法.您还可以使用 trampoline 任务在 Leiningen 退出后启动项目的 JVM，而不是将其作为子进程启动.

A: This is a limitation of the JVM's process-handling methods; none of them expose stdin correctly. This means that functions like read-line will not work as expected in most contexts, though the repl task necessarily includes a workaround. You can also use the trampoline task to launch your project's JVM after Leiningen's has exited rather than launching it as a subprocess.

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