NAME

       Sympa::LockedFile - Filehandle with locking

SYNOPSIS

         use Sympa::LockedFile;

         # Create filehandle acquiring lock.
         my $fh = Sympa::LockedFile->new('/path/to/file', 20, '+<') or die;
         # or,
         my $fh = Sympa::LockedFile->new();
         $fh->open('/path/to/file', 20, '+<') or die;

         # Operations...
         while (<$fh>) { ... }
         seek $fh, 0, 0;
         truncate $fh, 0;
         print $fh "blah blah\n";
         # et cetera.

         # Close filehandle releasing lock.
         $fh->close;

DESCRIPTION

       This class implements a filehandle with locking.

   Class Methods
       new ( [ $file, [ $blocking_timeout, [ $mode ] ] ] )
           Creates new object.  If any of optional parameters are specified, opens a file
           acquiring lock.

           Parameters:

           See open().

           Returns:

           New object or, if something went wrong, false value.

       last_error ( )
           Get a string describing the most recent error.

           Parameters:

           None.

           Returns:

           String or, if recent operation was success, "undef".

   Instance Methods
       Instances of Sympa::LockedFile support the methods provided by IO::File.

       open ( $file, [ $blocking_timeout, [ $mode ] ] )
           Opens a file specified by $file acquiring lock.

           Parameters:

           $file
               Path of file to be locked and opened.

           $blocking_timeout
               Programs will block up to the number of seconds specified by this option before
               returning undef (could not get a lock).  If negative value was given, programs
               will not block but fail immediately ("LOCK_NB").

               Default is 30.

               However, if existing lock is older than 1200 seconds i.e. 20 minutes, lock will be
               stolen.

           $mode
               Mode to open file.  If it implies any writing operations ('>', '>>', '+<', ...),
               tries to acquire exclusive lock ("LOCK_EX"), otherwise shared lock ("LOCK_SH").

               Default is '<'.

               Additionally, a special mode '+' will acquire exclusive lock without opening file.
               In this case the file does not have to exist.

               The numeric modes used for sysopen() (e.g. "O_CREAT") are not supported.

           Returns:

           New filehandle.  If acquiring lock failed, won't open file.  If opening file failed,
           releases acquired lock.  In both cases returns false value.

       close ( )
           Closes filehandle and releases lock on it.

           Note that destruction of instance will safely close filehandle and release lock.

           Parameters:

           None.

           Returns:

           If close succeeded, returns true value, otherwise false value.

           If filehandle had not been locked by current process, this method will safely close it
           and die.

       Following methods are specific to this module.

       basename ( [ $level ] )
           Gets base name of locked file.

       extend ( )
           Extends stale lock timeout.  The lock will never be stolen in 1200 seconds again.

           Parameters:

           None.

           Returns:

           If extension succeeded, returns true value, otherwise false value.

           If filehandle had not been locked by current process, this method will die doing
           nothing.

       rename ( $destfile )
           Renames file, closes filehandle and releases lock on it.  Filehandle must have
           acquired exclusive lock.

           Parameter:

           $destfile
               Destination path of renaming.

           Returns:

           If renaming succeeded, returns true value, otherwise false value and does not release
           lock.  In both cases filehandle is closed anyway.

           If filehandle had not been locked by current process, this method will die doing
           nothing.

       unlink ( )
           Deletes file and releases lock on it.

           Parameters:

           None.

           Returns:

           If unlink succeeded, returns true value, otherwise false value and does not release
           lock.

           If filehandle had not been locked by current process, this method will die without
           deleting file.

SEE ALSO

       "Functions for filehandles, files or directories" in perlfunc, "I/O Operators" in perlop,
       IO::File, File::NFSLock.

HISTORY

       Lock module written by Olivier Salauen appeared on Sympa 5.3.

       Support for NFS was added by Kazuo Moriwaka.

       Rewritten Sympa::LockedFile module was initially written by IKEDA Soji for Sympa 6.2.