On 9/12/07, Dr.Ruud <[EMAIL PROTECTED]> wrote:
snip
> Broken alternative;
snip
> $ perl -wle '$t="abc\ndefgh\n\nxyz"; print "<$1>" while $t =~ /(.*)/g'
snip
> But this variant might be handy:
> $ perl -wle '$t="abc\ndefgh\n\nxyz"; while ($t =~ /(.+)/g) { print "<$1>" }'
snip
> (main advantage: it doesn't create an immediate array)
>
> But I assume that a proper HTML parser will be the final answer.
snip
If the file returned is indeed HTML then an HTML parser is the right
answer. But if he is just fetching a text file with HTTP and wants to
read it line by line, then either split (faster) or open (less memory
usage) is the way to go. I would not recommend using a regex to get
just lines; however, if you are looking for something specific in the
entire file then a regex may be the way to go.
test of subs, output should be subname: 78 78
open: 78 78
regex1: 78 78
regex2: 78 78
split: 78 78
with 10 lines
Rate regex1 open regex2 split
regex1 53096/s -- -16% -45% -57%
open 63015/s 19% -- -35% -49%
regex2 96376/s 82% 53% -- -22%
split 123675/s 133% 96% 28% --
with 100 lines
Rate regex1 regex2 open split
regex1 5749/s -- -44% -55% -61%
regex2 10239/s 78% -- -20% -30%
open 12799/s 123% 25% -- -13%
split 14638/s 155% 43% 14% --
with 1000 lines
Rate regex1 regex2 open split
regex1 575/s -- -43% -60% -61%
regex2 1008/s 75% -- -30% -32%
open 1437/s 150% 43% -- -3%
split 1478/s 157% 47% 3% --
with 10000 lines
Rate regex1 regex2 open split
regex1 57.3/s -- -44% -61% -61%
regex2 103/s 79% -- -30% -30%
open 146/s 155% 42% -- -1%
split 148/s 158% 44% 1% --
#!/usr/bin/perl
use strict;
use warnings;
use Benchmark;
my $text = ("a" x 78 . "\n") x 2;
my %subs = (
split => sub {
my @a;
for my $line (split /\n/, $text) {
push @a, length $line;
}
return @a;
},
regex2 => sub {
my @a;
while ($text =~ /(.+)/g) {
my $line = $1;
push @a, length $line;
}
return @a;
},
regex1 => sub {
my @a;
while ($text =~ /(.*)/g) {
next unless $1;
my $line = $1;
push @a, length $line;
}
return @a;
},
open => sub {
my @a;
open my $f, "<", \$text;
while (my $line = <$f>) {
chomp $line;
push @a, length $line;
}
return @a;
},
);
print "test of subs, output should be subname: 78 78\n";
for my $sub (sort keys %subs) {
print "$sub: @{[$subs{$sub}->()]}\n";
}
for my $lines (10, 100, 1_000, 10_000) {
$text = ("a" x 78 . "\n") x $lines;
print "\nwith $lines lines\n";
Benchmark::cmpthese(-2, \%subs);
}
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