io::atomicfile(3)
NAME
IO::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!0;
$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!0;
$FH->delete;
### Write a temp file, but neither install it nor
delete it:
my $FH = IO::AtomicFile->open("bar.dat", "w");
print $FH "Hello!0;
$FH->detach;
DESCRIPTION
This module is intended for people who need to update
files reliably in the face of unexpected program termina
tion.
For example, you generally don't want to be halfway in the
middle of writing /etc/passwd and have your program termi
nate! Even the act of writing a single scalar to a file
handle is not atomic.
But this module gives you true atomic updates, via
rename(). When you open a file /foo/bar.dat via this mod
ule, 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.
AUTHOR
Eryq (eryq@zeegee.com). President, ZeeGee Software Inc
(http://www.zeegee.com).
REVISION
- $Revision: 2.101 $