<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <!--Rendered using the Haskell Html Library v0.2--> <HTML ><HEAD ><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=UTF-8" ><TITLE >System.IO.Utils</TITLE ><LINK HREF="haddock.css" REL="stylesheet" TYPE="text/css" ><SCRIPT SRC="haddock-util.js" TYPE="text/javascript" ></SCRIPT ><SCRIPT TYPE="text/javascript" >window.onload = function () {setSynopsis("mini_System-IO-Utils.html")};</SCRIPT ></HEAD ><BODY ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD CLASS="topbar" ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD ><IMG SRC="haskell_icon.gif" WIDTH="16" HEIGHT="16" ALT=" " ></TD ><TD CLASS="title" >MissingH-1.1.0.3: Large utility library</TD ><TD CLASS="topbut" ><A HREF="src/System-IO-Utils.html" >Source code</A ></TD ><TD CLASS="topbut" ><A HREF="index.html" >Contents</A ></TD ><TD CLASS="topbut" ><A HREF="doc-index.html" >Index</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="modulebar" ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD ><FONT SIZE="6" >System.IO.Utils</FONT ></TD ><TD ALIGN="right" ><TABLE CLASS="narrow" CELLSPACING="0" CELLPADDING="0" ><TR ><TD CLASS="infohead" >Portability</TD ><TD CLASS="infoval" >portable</TD ></TR ><TR ><TD CLASS="infohead" >Stability</TD ><TD CLASS="infoval" >provisional</TD ></TR ><TR ><TD CLASS="infohead" >Maintainer</TD ><TD CLASS="infoval" >John Goerzen <jgoerzen@complete.org></TD ></TR ></TABLE ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD CLASS="section4" ><B >Contents</B ></TD ></TR ><TR ><TD ><DL ><DT ><A HREF="#1" >Entire File Handle Utilities </A ></DT ><DD ><DL ><DT ><A HREF="#2" >Opened Handle Data Copying </A ></DT ><DT ><A HREF="#3" >Disk File Data Copying </A ></DT ></DL ></DD ><DT ><A HREF="#4" >Line Processing Utilities </A ></DT ><DT ><A HREF="#5" >Lazy Interaction </A ></DT ><DD ><DL ><DT ><A HREF="#6" >Character-based </A ></DT ><DT ><A HREF="#7" >Line-based </A ></DT ><DT ><A HREF="#8" >Misc. Lazy </A ></DT ></DL ></DD ><DT ><A HREF="#9" >Optimizations </A ></DT ></DL ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" >Description</TD ></TR ><TR ><TD CLASS="doc" ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" >Synopsis</TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="body" ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD CLASS="decl" ><A HREF="#v%3AhCopy" >hCopy</A > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b) => a -> b -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AhCopyProgress" >hCopyProgress</A > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > c, <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AIntegral" >Integral</A > a) => b -> c -> (<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Maybe.html#t%3AMaybe" >Maybe</A > a -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AInteger" >Integer</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Bool.html#t%3ABool" >Bool</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A >) -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Int.html#t%3AInt" >Int</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Maybe.html#t%3AMaybe" >Maybe</A > a -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AInteger" >Integer</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AhLineCopy" >hLineCopy</A > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b) => a -> b -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AlineCopy" >lineCopy</A > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AcopyFileLinesToFile" >copyFileLinesToFile</A > :: <A HREF="System-IO-HVFS.html#t%3AFilePath" >FilePath</A > -> <A HREF="System-IO-HVFS.html#t%3AFilePath" >FilePath</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AhPutStrLns" >hPutStrLns</A > :: <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a => a -> [<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >] -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AhGetLines" >hGetLines</A > :: <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a => a -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > [<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >]</TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AhInteract" >hInteract</A > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b) => a -> b -> (<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >) -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AhLineInteract" >hLineInteract</A > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b) => a -> b -> ([<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >] -> [<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >]) -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AlineInteract" >lineInteract</A > :: ([<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >] -> [<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >]) -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AlazyMapM" >lazyMapM</A > :: (a -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > b) -> [a] -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > [b]</TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AoptimizeForBatch" >optimizeForBatch</A > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3AoptimizeForInteraction" >optimizeForInteraction</A > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" ><A NAME="1" ><A NAME="1" >Entire File Handle Utilities </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section2" ><A NAME="2" ><A NAME="2" >Opened Handle Data Copying </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:hCopy" ><A NAME="v%3AhCopy" ></A ></A ><B >hCopy</B > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b) => a -> b -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#hCopy" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" >Copies from one handle to another in raw mode (using hGetContents). </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:hCopyProgress" ><A NAME="v%3AhCopyProgress" ></A ></A ><B >hCopyProgress</B ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#hCopyProgress" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="body" ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD CLASS="arg" >:: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > c, <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AIntegral" >Integral</A > a)</TD ><TD CLASS="rdoc" ></TD ></TR ><TR ><TD CLASS="arg" >=> b</TD ><TD CLASS="rdoc" >Input handle </TD ></TR ><TR ><TD CLASS="arg" >-> c</TD ><TD CLASS="rdoc" >Output handle </TD ></TR ><TR ><TD CLASS="arg" >-> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Maybe.html#t%3AMaybe" >Maybe</A > a -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AInteger" >Integer</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Bool.html#t%3ABool" >Bool</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="rdoc" >Progress function -- the bool is always False unless this is the final call </TD ></TR ><TR ><TD CLASS="arg" >-> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Int.html#t%3AInt" >Int</A ></TD ><TD CLASS="rdoc" ></TD ></TR ><TR ><TD CLASS="arg" >-> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Maybe.html#t%3AMaybe" >Maybe</A > a</TD ><TD CLASS="rdoc" ></TD ></TR ><TR ><TD CLASS="arg" >-> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AInteger" >Integer</A ></TD ><TD CLASS="rdoc" ></TD ></TR ><TR ><TD CLASS="ndoc" COLSPAN="2" >Copies from one handle to another in raw mode (using hGetContents). Takes a function to provide progress updates to the user. </TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:hLineCopy" ><A NAME="v%3AhLineCopy" ></A ></A ><B >hLineCopy</B > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b) => a -> b -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#hLineCopy" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Copies from one handle to another in text mode (with lines). Like hBlockCopy, this implementation is nice: </P ><PRE > hLineCopy hin hout = hLineInteract hin hout id </PRE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:lineCopy" ><A NAME="v%3AlineCopy" ></A ></A ><B >lineCopy</B > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#lineCopy" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" >Copies from <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/GHC-IO-Handle-FD.html#v%3Astdin" >stdin</A ></TT > to <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/GHC-IO-Handle-FD.html#v%3Astdout" >stdout</A ></TT > using lines. An alias for <TT ><A HREF="System-IO-Utils.html#v%3AhLineCopy" >hLineCopy</A ></TT > over <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/GHC-IO-Handle-FD.html#v%3Astdin" >stdin</A ></TT > and <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/GHC-IO-Handle-FD.html#v%3Astdout" >stdout</A ></TT >. </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section2" ><A NAME="3" ><A NAME="3" >Disk File Data Copying </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:copyFileLinesToFile" ><A NAME="v%3AcopyFileLinesToFile" ></A ></A ><B >copyFileLinesToFile</B > :: <A HREF="System-IO-HVFS.html#t%3AFilePath" >FilePath</A > -> <A HREF="System-IO-HVFS.html#t%3AFilePath" >FilePath</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#copyFileLinesToFile" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Copies one filename to another in text mode. </P ><P >Please note that the Unix permission bits are set at a default; you may need to adjust them after the copy yourself. </P ><P >This function is implemented using <TT ><A HREF="System-IO-Utils.html#v%3AhLineCopy" >hLineCopy</A ></TT > internally. </P ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" ><A NAME="4" ><A NAME="4" >Line Processing Utilities </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:hPutStrLns" ><A NAME="v%3AhPutStrLns" ></A ></A ><B >hPutStrLns</B > :: <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a => a -> [<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >] -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#hPutStrLns" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" >Given a list of strings, output a line containing each item, adding newlines as appropriate. The list is not expected to have newlines already. </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:hGetLines" ><A NAME="v%3AhGetLines" ></A ></A ><B >hGetLines</B > :: <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a => a -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > [<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >]</TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#hGetLines" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Given a handle, returns a list of all the lines in that handle. Thanks to lazy evaluation, this list does not have to be read all at once. </P ><P >Combined with <TT ><A HREF="System-IO-Utils.html#v%3AhPutStrLns" >hPutStrLns</A ></TT >, this can make a powerful way to develop filters. See the <TT ><A HREF="System-IO-Utils.html#v%3AlineInteract" >lineInteract</A ></TT > function for more on that concept. </P ><P >Example: </P ><PRE > main = do l <- hGetLines stdin hPutStrLns stdout $ filter (startswith "1") l </PRE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" ><A NAME="5" ><A NAME="5" >Lazy Interaction </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section2" ><A NAME="6" ><A NAME="6" >Character-based </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:hInteract" ><A NAME="v%3AhInteract" ></A ></A ><B >hInteract</B > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b) => a -> b -> (<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >) -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#hInteract" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >This is similar to the built-in <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#v%3Ainteract" >interact</A ></TT >, but works on any handle, not just stdin and stdout. </P ><P >In other words: </P ><PRE > interact = hInteract stdin stdout </PRE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section2" ><A NAME="7" ><A NAME="7" >Line-based </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:hLineInteract" ><A NAME="v%3AhLineInteract" ></A ></A ><B >hLineInteract</B > :: (<A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > a, <A HREF="System-IO-HVIO.html#t%3AHVIO" >HVIO</A > b) => a -> b -> ([<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >] -> [<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >]) -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#hLineInteract" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Line-based interaction over arbitrary handles. This is similar to wrapping hInteract with <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-List.html#v%3Alines" >lines</A ></TT > and <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-List.html#v%3Aunlines" >unlines</A ></TT >. </P ><P >One could view this function like this: </P ><PRE > hLineInteract finput foutput func = let newf = unlines . func . lines in hInteract finput foutput newf </PRE ><P >Though the actual implementation is this for efficiency: </P ><PRE > hLineInteract finput foutput func = do lines <- hGetLines finput hPutStrLns foutput (func lines) </PRE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:lineInteract" ><A NAME="v%3AlineInteract" ></A ></A ><B >lineInteract</B > :: ([<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >] -> [<A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A >]) -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#lineInteract" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Line-based interaction. This is similar to wrapping your interact functions with <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-List.html#v%3Alines" >lines</A ></TT > and <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-List.html#v%3Aunlines" >unlines</A ></TT >. This equality holds: </P ><PRE > lineInteract = hLineInteract stdin stdout </PRE ><P >Here's an example: </P ><PRE > main = lineInteract (filter (startswith "1")) </PRE ><P >This will act as a simple version of grep -- all lines that start with 1 will be displayed; all others will be ignored. </P ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section2" ><A NAME="8" ><A NAME="8" >Misc. Lazy </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:lazyMapM" ><A NAME="v%3AlazyMapM" ></A ></A ><B >lazyMapM</B > :: (a -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > b) -> [a] -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > [b]</TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#lazyMapM" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" >Applies a given function to every item in a list, and returns the new list. Unlike the system's mapM, items are evaluated lazily. </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" ><A NAME="9" ><A NAME="9" >Optimizations </A ></A ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:optimizeForBatch" ><A NAME="v%3AoptimizeForBatch" ></A ></A ><B >optimizeForBatch</B > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#optimizeForBatch" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" >Sets stdin and stdout to be block-buffered. This can save a huge amount of system resources since far fewer syscalls are made, and can make programs run much faster. </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:optimizeForInteraction" ><A NAME="v%3AoptimizeForInteraction" ></A ></A ><B >optimizeForInteraction</B > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/System-IO.html#t%3AIO" >IO</A > <A HREF="/usr/share/doc/ghc/html/libraries/ghc-prim-0.2.0.0/GHC-Unit.html#t%3A%28%29" >()</A ></TD ><TD CLASS="declbut" ><A HREF="src/System-IO-Utils.html#optimizeForInteraction" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" >Sets stdin and stdout to be line-buffered. This saves resources on stdout, but not many on stdin, since it it still looking for newlines. </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="botbar" >Produced by <A HREF="http://www.haskell.org/haddock/" >Haddock</A > version 2.6.1</TD ></TR ></TABLE ></BODY ></HTML >