File::NFSLock 1.20

File::NFSLock is a Perl module to do NFS (or not) locking.
SYNOPSIS
use File::NFSLock qw(uncache);
use Fcntl qw(LOCK_EX LOCK_NB);
my $file = "somefile";
### set up a lock - lasts until object looses scope
if (my $lock = new File::NFSLock {
file => $file,
lock_type => LOCK_EX|LOCK_NB,
blocking_timeout => 10, # 10 sec
stale_lock_timeout => 30 * 60, # 30 min
}) {
### OR
### my $lock = File::NFSLock->new($file,LOCK_EX|LOCK_NB,10,30*60);
### do write protected stuff on $file
### at this point $file is uncached from NFS (most recent)
open(FILE, "+<$file") || die $!;
### or open it any way you like
### my $fh = IO::File->open( $file, w ) || die $!
### update (uncache across NFS) other files
uncache("someotherfile1");
uncache("someotherfile2");
# open(FILE2,"someotherfile1");
### unlock it
$lock->unlock();
### OR
### undef $lock;
### OR let $lock go out of scope
}else{
die "I couldnt lock the file [$File::NFSLock::errstr]";
}
Program based of concept of hard linking of files being atomic across NFS. This concept was mentioned in Mail::Box::Locker (which was originally presented in Mail::Folder::Maildir). Some routine flow is taken from there -- particularly the idea of creating a random local file, hard linking a common file to the local file, and then checking the nlink status. Some ideologies were not complete (uncache mechanism, shared locking) and some coding was even incorrect (wrong stat index). File::NFSLock was written to be light, generic, and fast.
Enhancements:
- Perl