Re^2: printing the line after grepping

A beginner's version of that would be:

use strict;
use warnings;
use 5.010;


my $pattern = '0 Items in Feed & 0 New Fetched items';

open(my $INFILE, "<", "data2.txt") or die "There was a problem: $!";

while (my $line = <$INFILE>) {
    print $line if $line =~ /$pattern/;
}
[download]

If you write the while loop like this:

while (<$INFILE>) {
    
}
[download]

it becomes magical in perl. Every time through the while loop, the next line from the file will be read into a variable named $_. Calling print with no arguments will print $_, and a regex will match against $_ by default.

Comment on Re^2: printing the line after grepping Select or Download Code

Replies are listed 'Best First'.
Re^3: printing the line after grepping by ikegami (Patriarch) on Nov 11, 2009 at 17:50 UTC
Actually, `while (my $line = <$INFILE>)` is equally magical. `while (<$INFILE>) => while (defined($_ = <$INFILE>) while (my $line = <$INFILE>) => while (defined(my $line = <$INFILE>)` [download]	[reply] [d/l] [select]
Re^4: printing the line after grepping by 7stud (Deacon) on Nov 11, 2009 at 18:23 UTC
Equally magical? Nothing gets assigned to $_ in the latter case.	[reply]
Re^5: printing the line after grepping by ikegami (Patriarch) on Nov 11, 2009 at 18:29 UTC
Yes. In both cases, the code that's executed is different than the code in the file.	[reply]