Making a system call that returns the stdout output as a string

Question

Perl and PHP do this with backticks. For example,

$output = `ls`;

Returns a directory listing. A similar function, system(\"foo\")

Answer 1

Haskell:

import Control.Exception
import System.IO
import System.Process
main = bracket (runInteractiveCommand "ls") close $ \(_, hOut, _, _) -> do
    output <- hGetContents hOut
    putStr output
  where close (hIn, hOut, hErr, pid) =
          mapM_ hClose [hIn, hOut, hErr] >> waitForProcess pid

With MissingH installed:

import System.Cmd.Utils
main = do
    (pid, output) <- pipeFrom "ls" []
    putStr output
    forceSuccess pid

This is an easy operation in "glue" languages like Perl and Ruby, but Haskell isn't.