Q&A

Q&A

Q1:	Can I store the structures from Hour 13, "References and Structures," in a DBM file or a text file?
A1:	The short answer is no, not easily. The longer answer is yes, but first you need to convert the "structure" over to a string that represents the data and the structure that contains it, and you then need to use that as a value in the DBM-tied hash. The module to do so is Data::Dumper.
Q2:	How do I lock DBM files?
A2:	DBM files can be locked using the semaphore locking system shown previously. Simply use the get_lock() and release_lock() functions from Listing 15.3 and put these around the DBM open and close functions: get_lock(); dbmopen(%hash, "foo", 0644) || die "dmbopen: $!"; $hash{newkey}="Value"; dbmclose(%hash); release_lock();
Q3:	Can I somehow just check to see whether flock is going to pause without actually having it stop?
A3:	Yes you can. A value that can be passed to flock causes it not to pause. (It is called a nonblocking flock.) To find out whether a flock would pause, put a |LOCK_NB after the lock type like this: use Fcntl qw(:flock); # Attempt to get an exclusive lock, but don't wait for it. if (not flock( LF, LOCK_EX|LOCK_NB )) { print "Could not get the lock: $!"; } You can even wait for a lock for a while, and then print a message if you don't get it eventually: use Fcntl qw(:flock); $lock_attempts = 3; while (not flock( LF, LOCK_EX|LOCK_NB )) { sleep 5; # Wait 5 seconds $lock_attempts--; # Count down chances... die "Could not get lock!" if (not $attempts); }