NAMEIO::AtomicFile - write a file which is updated atomically + + + +
SYNOPSIS+ use IO::AtomicFile; ++
+ ### Write a temp file, and have it install itself when closed:
+ my $FH = IO::AtomicFile->open("bar.dat", "w");
+ print $FH "Hello!\n";
+ $FH->close || die "couldn't install atomic file: $!";
+
+
+ ### Write a temp file, but delete it before it gets installed:
+ my $FH = IO::AtomicFile->open("bar.dat", "w");
+ print $FH "Hello!\n";
+ $FH->delete;
+
+
+ ### Write a temp file, but neither install it nor delete it:
+ my $FH = IO::AtomicFile->open("bar.dat", "w");
+ print $FH "Hello!\n";
+ $FH->detach;
+
+
+
+ DESCRIPTIONThis module is intended for people who need to update files +reliably in the face of unexpected program termination. + + +
For example, you generally don't want to be halfway in the middle of +writing /etc/passwd and have your program terminate! Even +the act of writing a single scalar to a filehandle is not atomic. + + +
But this module gives you true atomic updates, via rename(). +When you open a file /foo/bar.dat via this module, you are actually +opening a temporary file /foo/bar.dat..TMP, and writing your +output there. The act of closing this file (either explicitly +via close(), or implicitly via the destruction of the object) +will cause rename() to be called... therefore, from the point +of view of the outside world, the file's contents are updated +in a single time quantum. + + +
To ensure that problems do not go undetected, the "close" method +done by the destructor will raise a fatal exception if the rename() +fails. The explicit close() just returns undef. + + +
You can also decide at any point to trash the file you've been +building. + + + +
AUTHOREryq (
REVISION$Revision: 2.101 $ + +