在Haskell中设置argv [0]？ [英] Setting argv[0] in Haskell?

问题描述

有没有办法在Haskell程序中设置 argv [0] （比如用ghc编译的程序）？

我在System.Environment中找到了 getProgName 和 withProgName 函数，但它似乎没有改变 ps 报告（Ubuntu）。

  import System.Environment 
 
 main = 
 do name<  -  getProgName 
 putStrLn $您好，我的名字是++名称
 withProgNameother$ do 
 newname< ;  -  getProgName 
 putStrLn $现在名称设置为++ newname 
 putStrLn你叫什么名字：
  - 允许时间运行ps 
 ans<  -  getLine 
 putStrLn $很高兴认识你，++ ans 
  

解决方案没有可移植的方法，但在Linux 2.6.9以上，进程名可以通过 prctl（） 使用 PR_SET_NAME 操作，所以我们只需要一点点的FFI就可以在Haskell中使用它。 （检查Hackage上是否有绑定通常是个好主意，但在这种情况下我找不到任何）。

  { - ＃LANGUAGE ForeignFunctionInterface＃ - } 
 
导入Foreign.C 
 
外部导入ccallsys / prctl.h prctl
 prctl :: CInt  - > CString  - > CULong  - > CULong  - > CULong  - > IO CInt 
 
 setProgName :: String  - > IO（）
 setProgName title = 
 withCString title $ \title' - > 
 res（ - ）prctl pr_set_name title'0 0 0 
 return（）
 where pr_set_name = 15 
  

对于 ps 来看，这似乎可以很好地改变名称。但是，当程序启动时，由 getProgName 返回的值似乎被缓存，因此您必须将它与 withProgName c>查看程序中的更改。

Is there a way to set argv[0] in a Haskell program (say, one compiled with ghc)?

I found the getProgName and withProgName functions in System.Environment, but it doesn't seem to change what ps reports (Ubuntu).

import System.Environment

main =
  do name <- getProgName
     putStrLn $ "Hello, my name is " ++ name
     withProgName "other" $ do
       newname <- getProgName
       putStrLn $ "Name now set to " ++ newname
       putStrLn "What is your name: "
       -- allow time to run ps
       ans <- getLine
       putStrLn $ "Pleased to meet you, " ++ ans

解决方案

There is no portable way of doing this, but on Linux 2.6.9 and up the process name can be changed with prctl() using the PR_SET_NAME operation, so we just need a little bit of FFI to use it from Haskell. (It's usually a good idea to check if there are any bindings on Hackage, but in this case I couldn't find any).

{-# LANGUAGE ForeignFunctionInterface #-}

import Foreign.C

foreign import ccall "sys/prctl.h prctl"
  prctl :: CInt -> CString -> CULong -> CULong -> CULong -> IO CInt

setProgName :: String -> IO ()
setProgName title =
  withCString title $ \title' -> do
    res <- prctl pr_set_name title' 0 0 0
    return ()
  where pr_set_name = 15

This seems to work fine for changing the name as seen by ps. However, the value returned by getProgName appears to be cached when the program starts, so you'll have to combine this with withProgName to see the change within your program.

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