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Answer: How do I get the Nth Character of a String?

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Q&A > strings > How do I get the Nth Character of a String? contributed by btrott

Some might consider using split and an index. The problem with this solution is that it's really slow, particularly as the string gets longer.

Here's some benchmarking code that'll show you:

#!/usr/local/bin/perl -w use strict; use Benchmark; use vars qw/$str/; $str = "123456789asgdjlaskjglkajblnlbnlaqjteoijqotijwojgl;akjglkj"; timethese(shift || 10000, { 'unpack' => sub { my $char = getn_unpack($str, 30) }, 'substr' => sub { my $char = getn_substr($str, 30) }, 'split' => sub { my $char = getn_split($str, 30) } }); sub getn_unpack { return unpack "x" . ($_[1]-1) . "a", $_[0]; } sub getn_substr { return substr $_[0], $_[1]-1, 1; } sub getn_split { return +(split //, $_[0])[$_[1]-1]; }
And here are the benchmark results:
Benchmark: timing 100000 iterations of split, substr, unpack... split: 20 secs (19.39 usr 0.00 sys = 19.39 cpu) substr: 0 secs ( 1.78 usr 0.00 sys = 1.78 cpu) unpack: 2 secs ( 2.89 usr 0.00 sys = 2.89 cpu)
The substr method is, obviously, the fastest, because that's what it's designed to do, basically.

unpack is also quite fast.
split has to split the entire string, construct an array of length($str) elements, then take an index.

So, the best way is to use substr.

Comment on Answer: How do I get the Nth Character of a String?
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Re: Answer: How do I get the Nth Character of a String?
by I0 (Priest) on Jan 20, 2001 at 10:58 UTC
    chr vec $_[0],$_[1]-1,8; #is slightly faster
    (but you should also think about why you want to do this, perhaps you're approaching the problem in a Cish way rather than a Perlish way)
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