> Hi
>
> I am a newbie to Perl , I was reading through one of the beginner level
> books on perl. I did not understand the concept of "Callbacks" and i
> have the following questions on it:
>
> 1. What are they ?
>
> 2. Why do we need them ?
>
> 3. What useful purpose do they achieve ?
>
> I was reading the following code to understand it but could not comprehend.
>
> *Code:*
>
> #!/usr/bin/perl
> use warnings;
> use strict;
> use File::Find;
> find ( \&callback, "/");
>
> sub callback {
> print $File::Find::name, "\n";
> }
>
> *End Of Code:*
>
> Thanks
> Jatin
Hi Jatin,
A callback is a reference to a subroutine. This reference when passed around,
allows other code to invoke it.
File::Find's find() method accepts a subroutine reference as the first argument
and a path in the filesystem as the second argument. find() traverses
recursively in '/' and calls your code reference (callback()) for each
file/directory it finds. Thus, your subroutine is able to get each item in the
path as soon as they are encountered by File::Find's find(). If find() was not
implemented to handle callbacks, the possible way to return encountered
file/directory names will be as an array or hash of file/directory names after
it has traversed and exhausted all possible file/directory names within the
path.
Regards,
Alan Haggai Alavi.
--
The difference makes the difference.
--
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
http://learn.perl.org/
