How to get the exit code of a system process?

Say I want to execute the command unrar x archivename from within Haskell.

What is the best way to do it and how do I get the exit code of 开发者_Python百科the command? If the command exited successfully I want to delete the archive else not.

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In the process library you will find the function readProcessWithExitCode, which does what you want. Something like:

(e,_,_) <- readProcessWithExitCode "unrar" ["unrar", "x", "-p-", "archivename"] ""
if e == ExitSuccess then ... else ...

There are also many other solutions, such as the system command. Take your pick.

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The readProcessWithExitCode function from System.Process should do the job.

import Control.Monad
import System.Directory
import System.Exit
import System.Process

main = do
    (exitCode, _, _) <- readProcessWithExitCode "unrar" ["x", "archivename"] ""
    when (exitCode == ExitSuccess) $ removeFile "archivename"