如何获得Haskell中创建的进程的进程ID？ [英] How to get the process ID of a created process in Haskell?

问题描述

也许我只是在System.Process API中丢失了一些明显的东西（ http://hackage.haskell.org/package/进程），但它似乎不支持获取创建的进程的原始PID。 API通常会返回一个可以很容易地使用的ProcessHandle，但这似乎并不符合我的部署需求。

我有一个情况，我想要产生一个长期运行的过程，记录它使用的PID，并能够在以后的时间（几天，几周，几个月）自动回来，并杀死旧的过程并重新启动一个新的过程。我确信有几种方法可以实现这种自动部署和重新启动，但是PID似乎是最简单的方法，不需要太多依赖于平台的代码。

<我对其他有关我的潜在问题的建议持开放态度，但对于我来说，在流程API中找不到任何直接PID引用（或转换为它们的方法）似乎很奇怪。这看起来像是对API的监督。

解决方案

以下是一些示例代码：

  import System.Process 
 import System.Process.Internals 
 
  - 如果进程已退出，则返回Just pid或Nothing 
 getPid ph = withProcessHandle ph go 
 where 
 go ph_ = case ph_ 
 OpenHandle x  - >返回$ Just x 
 ClosedHandle _  - > return Nothing 
 
 main = do 
（_，_，_，ph）<  -  createProcess $ shellecho $$
 getPid ph>> = print 
  

注意：我没有在Windows下测试过它，但它可以在OSX和Linux上使用。

对于Windows， Win32包在模块 System.Win32.Process 中有一个 getProcessId 函数，根据我的代码阅读，这应该工作：

$ p $ import System.Win32.Process（getProcessId）

main = do
（_，_，_，ph）< - createProcess $ shellecho $$
pid< - withProcessHandle ph go
print pid

where go（OpenHandle x）= fmap只需$ getProcessId x
go（ClosedHandle _）= return Nothing


我基于此的代码是 interruptProcessGroupOf （链接）

Maybe I'm just missing something obvious in the System.Process API (http://hackage.haskell.org/package/process), but it doesn't appear to support getting the raw PID of a process created. The API usually returns a ProcessHandle which can be used easily enough, but this doesn't appear to fulfill a deployment need I have.

I have a case where I want to spawn a long-running process, log the PID it's using, and be able to automatically come back at a later time (days, weeks, months) and kill the old process and re-start with a new process. I'm sure there are several ways to do this auto-deploy-and-restart, but PIDs seemed like the simplest way to do so without too much platform-dependent code.

I'm open to other suggestions about my underlying problem, but it seems odd to me that I can't find any direct PID references (or a way to convert to them) in the process API. This seems like an oversight of the API.

解决方案

Here is some example code:

import System.Process
import System.Process.Internals

-- | returns Just pid or Nothing if process has already exited
getPid ph = withProcessHandle ph go
  where
    go ph_ = case ph_ of
               OpenHandle x   -> return $ Just x
               ClosedHandle _ -> return Nothing

main = do
  (_,_,_,ph) <- createProcess $ shell "echo $$"
  getPid ph >>= print

Note: I haven't tested this under Windows, but it works on OSX and, presumably, Linux.

For Windows, the Win32 package has a getProcessId function in the module System.Win32.Process, and according to code I've read, this should work:

import System.Win32.Process (getProcessId)

main = do
    (_,_,_,ph) <- createProcess $ shell "echo $$"
    pid <- withProcessHandle ph go
    print pid

  where go (OpenHandle x)   = fmap Just $ getProcessId x 
        go (ClosedHandle _) = return Nothing

The code I am basing this on is the code for interruptProcessGroupOf (link)

这篇关于如何获得Haskell中创建的进程的进程ID？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！