Re: [Haskell-cafe] Execution of external command
On 14 Dec 2007, at 1:21 AM, Jules Bean wrote: Evan Laforge wrote: it seems that script may be not terminated if its output isn't read, so better code should be (_, h, g, _) - runInteractiveCommand script params result - hGetLine h hGetContents h = evaluate.length hGetContents g = evaluate.length Tangent here, but does anyone else think that something like hGetContentsEagerly would be handy in System.IO? YES! Jules PS we could give it a nice sensible name like hGetContents. We could renaming the existing hGetContents to hUnsafeGetContentsDontUseThisUnlessYouHaveSpentThreeMonthsLearningGHCs ExecutionSemanticsOrYouWillRegretIt On the contrary, it's great for writing filters. OTOH, using the result of hGetContents interleaved with other IO actions feels like a reversion to the bad old days of dialogs (which it is, of course). jcc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Execution of external command
Evan Laforge wrote: it seems that script may be not terminated if its output isn't read, so better code should be (_, h, g, _) - runInteractiveCommand script params result - hGetLine h hGetContents h = evaluate.length hGetContents g = evaluate.length Tangent here, but does anyone else think that something like hGetContentsEagerly would be handy in System.IO? YES! Jules PS we could give it a nice sensible name like hGetContents. We could renaming the existing hGetContents to hUnsafeGetContentsDontUseThisUnlessYouHaveSpentThreeMonthsLearningGHCsExecutionSemanticsOrYouWillRegretIt ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Execution of external command
On Thu, 2007-12-13 at 15:48 +0300, Bulat Ziganshin wrote: Hello haskell-cafe, please help me with selection of proper function to use i need to run external command with parameter and get its stdout, smth like this: output - system cmd param the code should be compatible with unix and windows, and it should be possible to execute scripts (so afaiu it should execute command via cmd/sh). i use ghc 6.6.1 and it will be great if this function will not require any non-bundled libs and be compatible with later ghc versions There is rawSystemStdout in Cabal which you might like to copy. It is portable to windows and several Haskell compilers but does use cpp to achieve that. It's also rather inefficient as it has to create a temporary file. It seems it is not possible to use pipes to get the stdout and have the resulting code be portable between Haskell implementations (it's a favourite peeve of mine). As the name suggests, rawSystemStdout uses rawSystem so does not necessarily do what you want with cmd/sh but you could easily adapt it to use system rather than rawSystem. http://darcs.haskell.org/cabal/Distribution/Simple/Utils.hs http://darcs.haskell.org/cabal/Distribution/Compat/TempFile.hs Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Execution of external command
Hi Bulat, You wrote: please help me with selection of proper function to use i need to run external command with parameter and get its stdout, smth like this: output - system cmd param the code should be compatible with unix and windows, and it should be possible to execute scripts (so afaiu it should execute command via cmd/sh). i use ghc 6.6.1 and it will be great if this function will not require any non-bundled libs and be compatible with later ghc versions OK, I'll bite. What's wrong with runInteractiveCommand? -Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Execution of external command
so, do (stdin,stdout,stderr,ph) - runInteractiveCommand script param waitForProcess ph when i should read stdout? before or after waitForProcess? If you are sure that your script will behave nicely (or don't care if it doesn't), how about just: (_, h, _, _) - runInteractiveCommand script params output - hGetContents h -Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Execution of external command
On Thu, 2007-12-13 at 15:06 +0200, Yitzchak Gale wrote: Hi Bulat, You wrote: please help me with selection of proper function to use i need to run external command with parameter and get its stdout, smth like this: output - system cmd param the code should be compatible with unix and windows, and it should be possible to execute scripts (so afaiu it should execute command via cmd/sh). i use ghc 6.6.1 and it will be great if this function will not require any non-bundled libs and be compatible with later ghc versions OK, I'll bite. What's wrong with runInteractiveCommand? It requires threads to use correctly and it is only available in GHC, not in hugs, nhc98 etc. It requires threads because you have to pull from both the stdout and stderr to prevent blocking. You could do it with non-blocking reads but not without busy-waiting. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
