even better...
__________________
On Thursday, April 11, 2002, at 01:17 PM, Timothy Johnson wrote:
>
> Just for those who haven't figured out why the first example is so
useful,
> consider what perl is doing in the following two snippets:
>
> 1
> ======
> open(INFILE,"myfile.txt");
> @file = <INFILE>;
> foreach(@file){
> do something to $_...
> }
>
> 2
> ======
> open(INFILE,"myfile.txt");
> while(<STDIN>){
> do something to $_...
> }
>
assume you meant:
while(<INFILE>)
> In the first example, Perl will load the entire contents of the file into
> memory, then perform any operations on the contents. This can really bog
> down your system, especially if you have, say, a 500MB file to parse.
The
> second example loads the file one line at a time. I learned this lesson
> the
> hard way.
>
>
of course, you could do:
open(INFILE,"myfile.txt");
for (<INFILE>)
{
# do something with $_
}
but, that isn't going to help understanding :)
> -----Original Message-----
> From: drieux [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, April 11, 2002 12:25 PM
> To: [EMAIL PROTECTED]
> Subject: Re: while and do
>
>
>
> On Thursday, April 11, 2002, at 12:02 , Teresa Raymond wrote:
>
>> Could someone explain the while and do w/ couple of examples? I have
yet
>> to use them, only using the foreach loop and if else stmts.
>
> the obvious ones are
>
> while(<STDIN>) {
>
> # bunch of stuff one wants to do with the STDIN stuff
> }
>
> or my all time basic
>
> while ( my ( $key, $val ) = each %someHash ) {
>
> # based upon key or val do the stuff for all elements of the
> hash
> }
>
> in the main I do not do 'do' things...
>
> ciao
> drieux
>
> ---
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