我如何在xmonad键绑定中使用readProcess的输出？ [英] How do I use the output of readProcess in an xmonad keybinding?

问题描述

好的，前段时间我正在考虑基于我盒子上脚本输出的xmonad中的键绑定效果。我最终决定不要这样做，因为不相关的原因，但我最近尝试做类似于学习Haskell的练习。

所以，给定函数：

p>

  test = readProcessecho[-n，gvim] [] 
  
 
 
 
这会抛出，因为测试返回IO String并且spawn期望一个String。 
 
 
 （（modm，xK_y），spawn（xmessage++ test））
  
确定。这很酷。我知道IO操作是不可预测的，所以应该将它们分开。精细。所以我在网上做了一些尝试，并得到了这个（放弃了xmessage，只想传递测试的输出）： 
 
 
 （（modm，xK_y），liftIO test>> = spawn）
  
 。它烦人地编译，但当我尝试绑定时没有任何反应。 （我也用spawnxmessage test替换了它），然后工作）
 
 
然后，我想也许我的函数有问题，所以我重复它，但从GCHi我得到gvim这是正确的。然后我把它写到haskell文件中：
 
 
  main = test>> = putStrLn 
 test = readProcess echo[-n，gvim] [] 
  
 p> 
 
 
那么，我出错的地方是什么？
 
 
 
编辑：解决方案是使用 runProcessWithInput 而不是 readProcess 。 
相关链接： https://ghc.haskell.org/trac/ghc / ticket / 5212   xmonad io binding not working  
解决方案
 更新 
显然，解决方案）使用 readProcessWithInput  
 
 
 
 原始答案  
 
 
您说过：
 
 
  liftIO test>> = spawn 
  code> 
不起作用，但如何： 
 
 
  liftIO test>> =（\ m  - > spawn（xmessage++ m））
  
另外请注意，由 readProcess 返回的字符串最后可能会有换行符，这可能会影响事物。
 
 
 
在这种情况下可以尝试更多的事情： 
 
 
  returngvim>> =（\ m  - > spawn（xmessage++ m））
 
 
 import Data.Char 
 
 do {m < -  liftIO test; spawn（xmessage++（filter isAlpha m））} 
  
第一个应该成功，因为它相当于 spawnxmessage grim。第二个将从 test 的输出中删除任何新行（确实是任何非字母）。
 
 
 
一些进一步的事情可能会揭示发生的事情： 
 
 
 
 
 
创建一个名为 / tmp /报告与这些内容：
 ＃！/ bin / sh 
（日期;回声/ tmp / report用args调用$ @）>> / tmp / output 
  
 
 
 
 
制作 / tmp / report  executable。
 
 
 
运行 / tmp / report 并确认两行附加到<$ c在您的monad配置中，使操作 spawn/ tmp / report A  / tmp / output  
 C $ C>。通过查看预期行是否附加到 / tmp / output 来测试行为。尝试使单行动为此：
  liftIO（readProcess/ tmp / report[B]）>> spawn/ tmp / report A
  
（注意我们使用> > 这里，而不是>> = 。）当你触发这个动作时，你应该看到 B 呼叫，也是 A 呼叫中的一个。  
 
根据您在文件 / tmp / output 中看到的内容，您应该能够确定 readProcess 命令甚至被执行以及 spawn 命令被触发。
 
Ok, so some time ago I was thinking of basing the effect of a keybinding in my xmonad based on the output of a script on my box. I eventually decided not to do that for unrelated reasons but I did recently try to do something similar just as an exercise in learning Haskell.

So, given the function:
test = readProcess "echo" ["-n", "gvim"] []
This throws up because test returns IO String and spawn expects a String.
((modm, xK_y), spawn ("xmessage " ++ test))
Ok. That's cool. I get it that IO operations are unpredictable and so they should be kept separate. Fine. So I did some poking around online and got to this (dropped the xmessage and just want to pass the output of test by itself):
((modm, xK_y), liftIO test >>= spawn)
This is worse. It annoyingly compiles but nothing happens when I try out the binding. (I also replaced it with just spawn "xmessage test" and that worked)

So, then I thought "Maybe there's something wrong with my function" so I repl it but from GCHi I get "gvim" which is correct. So then I write it to a haskell file:
main = test >>= putStrLn
test = readProcess "echo" ["-n", "gvim"] []
Also works correctly.

So, where did I go wrong?

EDIT: Solution was to use runProcessWithInput instead of readProcess. 
Related link: https://ghc.haskell.org/trac/ghc/ticket/5212 xmonad io binding not working
解决方案
Update

Apparently the solution (see the comments below) is to use readProcessWithInput

Original Answer

You said that:
liftIO test >>= spawn
didn't work, but how about:
liftIO test >>= (\m -> spawn ("xmessage " ++ m))
Also note that the string returned by readProcess likely will have a newline at the end, and that may be affecting things.

Some more things to try in this vein:
return "gvim" >>= (\m -> spawn ("xmessage " ++ m))


import Data.Char

do { m <- liftIO test;  spawn ("xmessage " ++ (filter isAlpha m)) }
The first one should succeed since it is equivalent to spawn "xmessage grim". The second one will strip any newlines (indeed, any non-letters) from the output of test.

Some further things which might shed light on what is going on:

Create a script called /tmp/report with these contents:
#!/bin/sh
( date; echo "/tmp/report was called with args" "$@") >> /tmp/output

Make /tmp/report executable.
Run /tmp/report and verify that two lines was appended to /tmp/output
In your monad config, make the action spawn "/tmp/report A". Test the action by seeing if the expected line is appended to /tmp/output.
Try making the monad action this:
liftIO (readProcess "/tmp/report" ["B"] "") >> spawn "/tmp/report A"
(Note we are using >> here, not >>=.) When you trigger the action you should see a report line for the B call and also one for the A call.
Based on what you see in the file /tmp/output you should be able to determine whether the readProcess command is even being executed as well as the spawn command is triggering.

                        
这篇关于我如何在xmonad键绑定中使用readProcess的输出？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！