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[2]: [Haskell-cafe] Execution of external command
Hello Jules, Friday, December 14, 2007, 12:21:30 PM, you wrote: PS we could give it a nice sensible name like hGetContents. We could renaming the existing hGetContents to hUnsafeGetContentsDontUseThisUnlessYouHaveSpentThreeMonthsLearningGHCsExecutionSemanticsOrYouWillRegretIt i have more advanced proposal - we should include in its name whole paper on its semantics so anyone using it will be clearly warned. moreover, any suggestion to use this function will automatically include exact description of its caveats that is again The Right Thing To Do :) -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Execution of external command
On Dec 14, 2007 10:38 AM, Bulat Ziganshin [EMAIL PROTECTED] wrote: hUnsafeGetContentsDontUseThisUnlessYouHaveSpentThreeMonthsLearningGHCsExecutionSemanticsOrYouWillRegretIt i have more advanced proposal - we should include in its name whole paper on its semantics so anyone using it will be clearly warned. moreover, any suggestion to use this function will automatically include exact description of its caveats that is again The Right Thing To Do :) Until, that is, the first library appears on Hackage that aliases the name to ohBugger :-) - Benja ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Execution of external command
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 -- Best regards, Bulat mailto:[EMAIL PROTECTED] ___ 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[2]: [Haskell-cafe] Execution of external command
Hello Duncan, Thursday, December 13, 2007, 4:10:26 PM, you wrote: i need to run external command with parameter and get its stdout, smth 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). i don't need to interact with program, just get its whole output (one line) after it was finished. btw, afair, there was problems in windows with redirection of cmd.exe output (in particular when running executables from command files) separate windows and unix versions are ok for me, i just need them both. and i need only ghc support taking this all into account, where i should look? -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ 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[2]: [Haskell-cafe] Execution of external command
Hello Yitzchak, Thursday, December 13, 2007, 4:36:48 PM, you wrote: 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 am i correctly understand that i don't need to waitForProcess and, if script behaves correctly, hGetContents will read its whole output? -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Execution of external command
On Thu, 2007-12-13 at 16:27 +0300, Bulat Ziganshin wrote: Hello Duncan, Thursday, December 13, 2007, 4:10:26 PM, you wrote: i need to run external command with parameter and get its stdout, smth 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). i don't need to interact with program, just get its whole output (one line) after it was finished. btw, afair, there was problems in windows with redirection of cmd.exe output (in particular when running executables from command files) separate windows and unix versions are ok for me, i just need them both. and i need only ghc support taking this all into account, where i should look? Use just the GHC bit from the code I pointed at: bracket (liftM2 (,) (openTempFile tmpDir cmdstdout) (openFile devNull WriteMode)) -- We need to close tmpHandle or the file removal fails on Windows (\((tmpName, tmpHandle), nullHandle) - do hClose tmpHandle removeFile tmpName hClose nullHandle) $ \((tmpName, tmpHandle), nullHandle) - do cmdHandle - runProcess path args Nothing Nothing Nothing (Just tmpHandle) (Just nullHandle) exitCode - waitForProcess cmdHandle output - readFile tmpName evaluate (length output) return (output, exitCode) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[4]: [Haskell-cafe] Execution of external command
Hello Duncan, Thursday, December 13, 2007, 4:43:17 PM, you wrote: Use just the GHC bit from the code I pointed at: thank you, Duncan. are there any objections against simplest code proposed by Yitzchak? i.e. (_, h, _, _) - runInteractiveCommand script params output - hGetContents h taking into account that bad-behaved scripts are not my headache? -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ 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
Re[2]: [Haskell-cafe] Execution of external command
Hello gwern0, Thursday, December 13, 2007, 4:43:02 PM, you wrote: to get at stdout. I don't think this would go through cmd/sh, but honestly, specifying a particular interpreter breaks your portability anyway these scripts will be written by users so they don't need to be the same for winunix. i guess that users will prefer to use perl or something like this for these scripts and afaiu in both windows and linux this need to go through sh/cmd 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 am i right? -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Execution of external command
Bulat Ziganshin wrote: to Yitzchak: and you've asked what's wrong with runInteractiveCommand? :))) It was a good question. It prompted Duncan to post some really cool stuff, and we all learned something. -Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Execution of external command
On Thu, 2007-12-13 at 17:08 +0300, Bulat Ziganshin wrote: Hello Duncan, Thursday, December 13, 2007, 4:51:20 PM, you wrote: OK, I'll bite. What's wrong with runInteractiveCommand? 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. may be this will be ok (with -threaded)? No need for -threaded. (_, stdout, stderr, _) - runInteractiveCommand script params forkIO (hGetContents stderr = evaluate.length) result - hGetLine stdout hGetContents stdout = evaluate.length Yep, that'll work. awkward, but still shorter than code from Cabal The Cabal code has to work with ghc-6.2 - 6.8, hugs, nhc98 and jhc. It cannot use threads. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[4]: [Haskell-cafe] Execution of external command
Hello Duncan, Thursday, December 13, 2007, 5:38:24 PM, you wrote: Yep, that'll work. Spencer Janssen added that i should use waitForProcess - otherwise on unix it will leave a zombie Yitzchak, Duncan, gwern and Spencer. thank you very much for all your answers, i'm sure that i'll have much longer learning curve without your help! The Cabal code has to work with ghc-6.2 - 6.8, hugs, nhc98 and jhc. It cannot use threads. you've complained that there is no such functionality in std libs. may be it's worth making new hackage library, smth like Process? -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Execution of external command
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? When I am reading lots of little files I worry about open file limits. And besides, it seems like unsafeInterleaveIO can result in IO exceptions coming from pure code, so why use it if you don't have to? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] Execution of external command
qdunkan: 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? When I am reading lots of little files I worry about open file limits. And besides, it seems like unsafeInterleaveIO can result in IO exceptions coming from pure code, so why use it if you don't have to? I'll put a System.IO.Strict up on the weekend. Until then, perhaps use, as I sometimes do: import qualified Data.ByteString as S hGetContentsStrict = S.unpack `fmap` S.hGetContents Cheers, Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
