205 lines
5.0 KiB
HTML
205 lines
5.0 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of IO::Wrap</TITLE>
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</HEAD><BODY>
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<H1>IO::Wrap</H1>
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Section: User Contributed Perl Documentation (3pm)<BR>Updated: 2019-02-28<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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IO::Wrap - wrap raw filehandles in IO::Handle interface
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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use IO::Wrap;
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### Do stuff with any kind of filehandle (including a bare globref), or
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### any kind of blessed object that responds to a print() message.
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###
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sub do_stuff {
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my $fh = shift;
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### At this point, we have no idea what the user gave us...
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### a globref? a FileHandle? a scalar filehandle name?
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$fh = wraphandle($fh);
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### At this point, we know we have an IO::Handle-like object!
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$fh->print("Hey there!");
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...
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}
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</PRE>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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Let's say you want to write some code which does I/O, but you don't
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want to force the caller to provide you with a FileHandle or IO::Handle
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object. You want them to be able to say:
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<P>
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<PRE>
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do_stuff(\*STDOUT);
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do_stuff('STDERR');
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do_stuff($some_FileHandle_object);
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do_stuff($some_IO_Handle_object);
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</PRE>
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<P>
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And even:
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<P>
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<PRE>
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do_stuff($any_object_with_a_print_method);
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</PRE>
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<P>
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Sure, one way to do it is to force the caller to use <B>tiehandle()</B>.
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But that puts the burden on them. Another way to do it is to
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use <B>IO::Wrap</B>, which provides you with the following functions:
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<DL COMPACT>
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<DT id="1">wraphandle <FONT SIZE="-1">SCALAR</FONT><DD>
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This function will take a single argument, and ``wrap'' it based on
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what it seems to be...
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<DL COMPACT><DT id="2"><DD>
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<DL COMPACT>
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<DT id="3">•<DD>
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<B>A raw scalar filehandle name,</B> like <TT>"STDOUT"</TT> or <TT>"Class::HANDLE"</TT>.
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In this case, the filehandle name is wrapped in an IO::Wrap object,
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which is returned.
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<DT id="4">•<DD>
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<B>A raw filehandle glob,</B> like <TT>"\*STDOUT"</TT>.
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In this case, the filehandle glob is wrapped in an IO::Wrap object,
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which is returned.
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<DT id="5">•<DD>
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<B>A blessed FileHandle object.</B>
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In this case, the FileHandle is wrapped in an IO::Wrap object if and only
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if your FileHandle class does not support the <TT>"read()"</TT> method.
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<DT id="6">•<DD>
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<B>Any other kind of blessed object,</B> which is assumed to be already
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conformant to the IO::Handle interface.
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In this case, you just get back that object.
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</DL>
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</DL>
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<DL COMPACT><DT id="7"><DD>
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</DL>
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</DL>
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<P>
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If you get back an IO::Wrap object, it will obey a basic subset of
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the <FONT SIZE="-1">IO::</FONT> interface. That is, the following methods (note: I said
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<I>methods</I>, not named operators) should work on the thing you get back:
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<P>
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<PRE>
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close
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getline
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getlines
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print ARGS...
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read BUFFER,NBYTES
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seek POS,WHENCE
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tell
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</PRE>
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<A NAME="lbAE"> </A>
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<H2>NOTES</H2>
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Clearly, when wrapping a raw external filehandle (like \*STDOUT),
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I didn't want to close the file descriptor when the ``wrapper'' object is
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destroyed... since the user might not appreciate that! Hence,
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there's no <FONT SIZE="-1">DESTROY</FONT> method in this class.
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<P>
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When wrapping a FileHandle object, however, I believe that Perl will
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invoke the FileHandle::DESTROY when the last reference goes away,
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so in that case, the filehandle is closed if the wrapped FileHandle
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really was the last reference to it.
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<A NAME="lbAF"> </A>
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<H2>WARNINGS</H2>
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This module does not allow you to wrap filehandle names which are given
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as strings that lack the package they were opened in. That is, if a user
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opens <FONT SIZE="-1">FOO</FONT> in package Foo, they must pass it to you either as <TT>"\*FOO"</TT>
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or as <TT>"Foo::FOO"</TT>. However, <TT>"STDIN"</TT> and friends will work just fine.
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<A NAME="lbAG"> </A>
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<H2>VERSION</H2>
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<TT>$Id:</TT> Wrap.pm,v 1.2 2005/02/10 21:21:53 dfs Exp $
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<A NAME="lbAH"> </A>
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<H2>AUTHOR</H2>
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<DL COMPACT>
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<DT id="8">Primary Maintainer<DD>
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Dianne Skoll (<I><A HREF="mailto:dfs@roaringpenguin.com">dfs@roaringpenguin.com</A></I>).
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<DT id="9">Original Author<DD>
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Eryq (<I><A HREF="mailto:eryq@zeegee.com">eryq@zeegee.com</A></I>).
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President, ZeeGee Software Inc (<I><A HREF="http://www.zeegee.com">http://www.zeegee.com</A></I>).
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<P>
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</DL>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="10"><A HREF="#lbAB">NAME</A><DD>
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<DT id="11"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="12"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="13"><A HREF="#lbAE">NOTES</A><DD>
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<DT id="14"><A HREF="#lbAF">WARNINGS</A><DD>
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<DT id="15"><A HREF="#lbAG">VERSION</A><DD>
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<DT id="16"><A HREF="#lbAH">AUTHOR</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:46 GMT, March 31, 2021
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</BODY>
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</HTML>
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