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<html><head><title>IPC::Open2 (Programming Perl)</title><!-- STYLESHEET --><link rel="stylesheet" type="text/css" href="../style/style1.css"><!-- METADATA --><!--Dublin Core Metadata--><meta name="DC.Creator" content=""><meta name="DC.Date" content=""><meta name="DC.Format" content="text/xml" scheme="MIME"><meta name="DC.Generator" content="XSLT stylesheet, xt by James Clark"><meta name="DC.Identifier" content=""><meta name="DC.Language" content="en-US"><meta name="DC.Publisher" content="O'Reilly & Associates, Inc."><meta name="DC.Source" content="" scheme="ISBN"><meta name="DC.Subject.Keyword" content=""><meta name="DC.Title" content="IPC::Open2"><meta name="DC.Type" content="Text.Monograph"></head><body><!-- START OF BODY --><!-- TOP BANNER --><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home"><map name="banner-map"><AREA SHAPE="RECT" COORDS="0,0,466,71" HREF="index.htm" ALT="Programming Perl"><AREA SHAPE="RECT" COORDS="467,0,514,18" HREF="jobjects/fsearch.htm" ALT="Search this book"></map><!-- TOP NAV BAR --><div class="navbar"><table width="515" border="0"><tr><td align="left" valign="top" width="172"><a href="ch32_29.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0"></a></td><td align="center" valign="top" width="171"><a href="ch32_01.htm">Chapter 32: Standard Modules</a></td><td align="right" valign="top" width="172"><a href="ch32_31.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0"></a></td></tr></table></div><hr width="515" align="left"><!-- SECTION BODY --><h2 class="sect1">32.30. IPC::Open2</h2><p><blockquote><pre class="programlisting">use IPC::Open2;local(*HIS_OUT, *HIS_IN); # Create local handles if needed.$childpid = open2(*HIS_OUT, *HIS_IN, $program, @args) or die "can't open pipe to $program: $!";print HIS_IN "here's your input\n";$his_output = <HIS_IN>;close(HIS_OUT);close(README);waitpid($childpid, 0);</pre></blockquote>The <tt class="literal">IPC::Open2</tt> module's one exported function, <tt class="literal">open2</tt>, startsup another program and provides both read and write access to that command.The first two arguments should be valid filehandles (or else emptyvariables into which autogenerated filehandles can be placed). Theremaining arguments are the program plus its arguments, which ifpassed in separately will not be subject to shell interpolation.This module does not reap the child process after it exits. Except forshort programs where it's acceptable to let the operating systemtake care of this, you need to do this yourself. This is normallyas simple as calling <tt class="literal">waitpid $pid, 0</tt> when you're done with thatchild process. Failure to do this can result in an accumulationof defunct ("zombie") processes.</p><p>In practice, this module doesn't work well with many programs becauseof the way buffering works in C's standard I/O library. If youcontrol the source code to both programs, however, you can easilycircumvent this restriction by flushing your output buffers morefrequently than the default. If you don't, programs can be annoyinglymiserly in their hoarding of output. Another potential pitfall isdeadlock: if both processes are reading at the same time, and noone is writing, then your program will hang. See <a href="ch16_01.htm">Chapter 16, "Interprocess Communication"</a> for more discussion.</p><!-- BOTTOM NAV BAR --><hr width="515" align="left"><div class="navbar"><table width="515" border="0"><tr><td align="left" valign="top" width="172"><a href="ch32_29.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0"></a></td><td align="center" valign="top" width="171"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0"></a></td><td align="right" valign="top" width="172"><a href="ch32_31.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0"></a></td></tr><tr><td align="left" valign="top" width="172">32.29. IO::Socket</td><td align="center" valign="top" width="171"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0"></a></td><td align="right" valign="top" width="172">32.31. IPC::Open3</td></tr></table></div><hr width="515" align="left"><!-- LIBRARY NAV BAR --><img src="../gifs/smnavbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links"><p><font size="-1"><a href="copyrght.htm">Copyright © 2001</a> O'Reilly & Associates. All rights reserved.</font></p><map name="library-map"> <area shape="rect" coords="2,-1,79,99" href="../index.htm"><area shape="rect" coords="84,1,157,108" href="../perlnut/index.htm"><area shape="rect" coords="162,2,248,125" href="../prog/index.htm"><area shape="rect" coords="253,2,326,130" href="../advprog/index.htm"><area shape="rect" coords="332,1,407,112" href="../cookbook/index.htm"><area shape="rect" coords="414,2,523,103" href="../sysadmin/index.htm"></map><!-- END OF BODY --></body></html>⌨️ 快捷键说明
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