Re: Going through a big file

[LanX]

in reply to Going through a big file [solved]

> First I tried the obvious

open in, shift @ARGV; 
for(<in>){ 

Obvious?

You will hardly find any example in the perldocs ever trying this.

Rather

open in, shift @ARGV; 
while (<in>){ 

or better

open my $in, '<', shift @ARGV; 
while (my $line = <$in>){ 

Explanation

your code is semantically equivalent to

my @temp_list=<in>;
for(@temp_list){ 

slurping the whole file as a first step.

for expects a list and evaluates in list context¹, so it's greedily swallowing all at once.

But while iterates in scalar context, that is line by line (as defined by '$/')

¹) with a little magical exception in recent Perl versions (>= 5.8 ?) regarding ranges, which isn't relevant here

[Chuma]

Oh! Well, that explains it. Thanks very much!