123 lines
3.3 KiB
HTML
123 lines
3.3 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::AtomicFile</TITLE>
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</HEAD><BODY>
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<H1>IO::AtomicFile</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::AtomicFile - write a file which is updated atomically
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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::AtomicFile;
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### Write a temp file, and have it install itself when closed:
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my $FH = IO::AtomicFile->open("bar.dat", "w");
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print $FH "Hello!\n";
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$FH->close || die "couldn't install atomic file: $!";
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### Write a temp file, but delete it before it gets installed:
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my $FH = IO::AtomicFile->open("bar.dat", "w");
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print $FH "Hello!\n";
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$FH->delete;
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### Write a temp file, but neither install it nor delete it:
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my $FH = IO::AtomicFile->open("bar.dat", "w");
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print $FH "Hello!\n";
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$FH->detach;
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</PRE>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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This module is intended for people who need to update files
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reliably in the face of unexpected program termination.
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<P>
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For example, you generally don't want to be halfway in the middle of
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writing <I>/etc/passwd</I> and have your program terminate! Even
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the act of writing a single scalar to a filehandle is <I>not</I> atomic.
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<P>
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But this module gives you true atomic updates, via <B>rename()</B>.
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When you open a file <I>/foo/bar.dat</I> via this module, you are <I>actually</I>
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opening a temporary file <I>/foo/bar.dat..TMP</I>, and writing your
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output there. The act of closing this file (either explicitly
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via <B>close()</B>, or implicitly via the destruction of the object)
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will cause <B>rename()</B> to be called... therefore, from the point
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of view of the outside world, the file's contents are updated
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in a single time quantum.
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<P>
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To ensure that problems do not go undetected, the ``close'' method
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done by the destructor will raise a fatal exception if the <B>rename()</B>
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fails. The explicit <B>close()</B> just returns undef.
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<P>
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You can also decide at any point to trash the file you've been
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building.
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<A NAME="lbAE"> </A>
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<H2>AUTHOR</H2>
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<A NAME="lbAF"> </A>
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<H3>Primary Maintainer</H3>
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Dianne Skoll (<I><A HREF="mailto:dfs@roaringpenguin.com">dfs@roaringpenguin.com</A></I>).
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<A NAME="lbAG"> </A>
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<H3>Original Author</H3>
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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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<A NAME="lbAH"> </A>
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<H2>REVISION</H2>
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<TT>$Revision:</TT> 1.2 $
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<P>
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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="1"><A HREF="#lbAB">NAME</A><DD>
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<DT id="2"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="3"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="4"><A HREF="#lbAE">AUTHOR</A><DD>
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<DL>
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<DT id="5"><A HREF="#lbAF">Primary Maintainer</A><DD>
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<DT id="6"><A HREF="#lbAG">Original Author</A><DD>
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</DL>
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<DT id="7"><A HREF="#lbAH">REVISION</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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