如何检索从Haskell执行的外部程序的输出？ [英] How to retrieve output of external program executed from Haskell?

问题描述

我想从Haskell运行一个外部程序并检索其输出和错误流的内容。在其中一个库中，我找到了这段代码：

  runProcess :: FilePath  - > [字符串]  - > IO（ExitCode，String，String）
 runProcess prog args = do 
（_，o，e，p）<  -  runInteractiveProcess编程参数Nothing Nothing 
 hSetBuffering o NoBuffering 
 hSetBuffering e NoBuffering 
 sout < -  hGetContents o 
 serr<  -  hGetContents e 
 ecode<  -  length sout'seq` waitForProcess p 
 return（ecode，sout，serr）
  

这是正确的做法吗？在这里有一些我不明白的地方：为什么流设置为 NoBuffering ？为什么长度sout'seq'？这感觉像是某种黑客。另外，我想将输出和错误流合并为一个，以获得与在命令行上执行 2>& 1 相同的效果。如果可能的话，我想避免使用专用I / O库，并依赖GHC提供的标准软件包。

解决方案

使用Shelly在Haskell中进行类似shell的编程的模块：

http://hackage.haskell.org/package/shelly-1.4.1/docs/Shelly.html

I want to run an external program from Haskell and retrieve contents of its output and error streams. In one of the libraries I found this code:

runProcess :: FilePath -> [String] -> IO (ExitCode, String, String)
runProcess prog args = do
  (_,o,e,p) <- runInteractiveProcess prog args Nothing Nothing
  hSetBuffering o NoBuffering
  hSetBuffering e NoBuffering
  sout  <- hGetContents o
  serr  <- hGetContents e
  ecode <- length sout `seq` waitForProcess p
  return (ecode, sout, serr)

Is this the right thing to do it? There are some things I don't understand here: why streams are set to NoBuffering? Why length sout 'seq' ? This feels like some kind of hack. Also, I would like to merge output and error streams into one to get the same effect as if I did 2>&1 on the command line. If possible I want to avoid using dedicated I/O libraries and rely on standard packages provided with GHC.

解决方案

Use Shelly, a module for shell-like programming in Haskell:

http://hackage.haskell.org/package/shelly-1.4.1/docs/Shelly.html

这篇关于如何检索从Haskell执行的外部程序的输出？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！