Chapter 2

module could be changed to automatically open the log file as soon as possible 

during compile time. To cause code to be run at compile time, move the code from 

open_log() into a BEGIN block:

BEGIN {

   open(LOG_FILE, ">>logs/boa.log") or die "Unable to open log : $!";

   print LOG_FILE "BOA log started: " . localtime(time) . "\n";

}

Now the log file is opened as soon as the BOA::Logger module is compiled. The 

downside here is that the location of the log file is hard coded into BOA::Logger.

END

It is often useful to know when an application exited. BOA::Logger can provide this 

by registering an action to take place when the application exits. This is done with 

an END block the opposite of the BEGIN block described earlier.

END {

   print LOG_FILE "BOA log exited: " . localtime(time) . "\n";

   close LOG_FILE or die "Unable to close log/boa.log : $!";

}

As an added bonus I get to feel like a good citizen by closing the LOG_FILE file han 

dle instead of letting global destruction do it for me. Global destruction refers to 

the phase in a Perl program's life when the interpreter is shutting down and will 

automatically free all resources held by the program. END blocks are often used to 

clean up resources obtained during BEGIN blocks.

Error Reporting

BOA::Logger is a careful module it always checks to make sure system calls like 

open() and close() succeed. When they don't, BOA::Logger calls die(), which will 

cause the program to exit if not caught by an eval.

10

 This is all well and good, but 

unfortunately the error messages generated aren't very helpful they make it look 

as though there's a problem in BOA::Logger. For example, if you call open_log() on 

a file that can't be opened, you'll receive the following error message:

Unable to open /path/to/log : No such file or directory at BOA/Logger.pm line 8.

10. This is Perl's poor man exception handling. For a more evolved system, see the Exception 

module on CPAN.

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