ch25_04.htm
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<html><head><title>System Interaction (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="System Interaction"><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="ch25_03.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0"></a></td><td align="center" valign="top" width="171"><a href="ch25_01.htm">Chapter 25: Portable Perl</a></td><td align="right" valign="top" width="172"><a href="ch25_05.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">25.4. System Interaction</h2><p><a name="INDEX-4340"></a>Platforms that rely on a graphical user interface sometimeslack command lines, so programs requiring a command-line interfacemight not work everywhere. You can't do much about this, except upgrade.</p><p>Some other tips:</p><ul><li><p><a name="INDEX-4341"></a>Some platforms can't delete or rename files that are in use, so remember to <tt class="literal">close</tt> files when you are donewith them. Don't <tt class="literal">unlink</tt> or <tt class="literal">rename</tt> an open file. Don't <tt class="literal">tie</tt>or <tt class="literal">open</tt> a file already tied or opened; <tt class="literal">untie</tt> or <tt class="literal">close</tt> itfirst.</p></li><li><p>Don't open the same file more than once at a time for writing, since someoperating systems put mandatory locks on such files.</p></li><li><p><a name="INDEX-4342"></a><a name="INDEX-4343"></a>Don't depend on a specific environment variable existing in<tt class="literal">%ENV</tt>, and don't assume that anything in<tt class="literal">%ENV</tt> will be case sensitive or case preserving.Don't assume Unix inheritance semantics for environmentvariables; on some systems, they may be visible to all other processes.</p></li><li><p><a name="INDEX-4344"></a><a name="INDEX-4345"></a>Don't use signals or <tt class="literal">%SIG</tt>.</p></li><li><p><a name="INDEX-4346"></a><a name="INDEX-4347"></a>Try to avoid filename globbing. Use <tt class="literal">opendir</tt>, <tt class="literal">readdir</tt>, and<tt class="literal">closedir</tt> instead. (As of release 5.6.0 of Perl, basic filenameglobbing is much more portable than it was, but some systems may stillchafe under the Unixisms of the default interface if you try to getfancy.)</p></li><li><p><a name="INDEX-4348"></a>Don't assume specific values of the error numbers or strings stored in<tt class="literal">$!</tt>.</p></li></ul><!-- 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="ch25_03.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="ch25_05.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0"></a></td></tr><tr><td align="left" valign="top" width="172">25.3. Files and Filesystems</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">25.5. Interprocess Communication (IPC)</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. 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