Anees wrote:
Dear friends:
Hello,
I am a perl begineer. I have created an script which prints each 100th
record from the file as shown below:
#!/usr/bin/perl
use warnings;
use strict;
$maxRecords=20000;
$steps=100;
$index=1;
$recCounter=0;
while (<>){
That is short for:
while ( defined( $_ = <> ) ) {
$ perl -MO=Deparse -e'while (<>) {}'
while (defined($_ = <ARGV>)) {
();
}
-e syntax OK
if(defined) {
So this test is superfluous because the while conditional already tests
for definedness.
if (($index % $steps) == 0) {
Perl provides the $. variable so you don't need $index:
unless ( $. % $steps ) {
print $_;
$recCounter++;
}
if($recCounter > $maxRecords){ break; }
$index++;
}
}
The above script works fine. But when I modify the script as follows:
#!/usr/bin/perl
use warnings;
use strict;
$maxRecords=20000;
$steps=100;
$index=1;
$recCounter=0;
while (<> && defined){
When you add the "&& defined" the assignment to $_ is not done nor the
test for definedness.
$ perl -MO=Deparse -e'while (<> && defined) {}'
while (<ARGV> and defined $_) {
();
}
-e syntax OK
if (($index % $steps) == 0) {
print $_;
$recCounter++;
}
if($recCounter > $maxRecords){ break; }
$index++;
}
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
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