Good catch. That's what I meant, alright.
-----Original Message-----
From: bob ackerman [mailto:[EMAIL PROTECTED]]
Sent: Thursday, April 11, 2002 2:34 PM
To: Timothy Johnson
Cc: [EMAIL PROTECTED]
Subject: Re: while and do
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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