CODEWITHSUNDEEP
perl
Zilore Mumba
Zilore Mumba

Reputation: 1500

Perl search and replace multiple strings in one pass

I have the following Perl code, which works without any error. I am wondering if it is possible to make the four replacements in the foreach loop in one pass and delete the whole line matching the fifth replacement. I do not understand the suggested solutions I have gone through so far, I am trying to avoid using hashes. I will be most appreciative.

#!/usr/bin/perl -w
use strict;
use warnings;
                                                                            
my @data=<DATA>;
foreach $lines (@data){
$lines =~ s/\//9/g;
$lines =~ s/333/33300/g;
$lines =~ s/555/55500/g;
$lines =~ s/=|==//g;
$lines =~ s/NIL|N I L//g;       # preferably delete this whole line
}

print "@lines\n";
exit 0;


__DATA__
63740 32575 40606 10217 20159 48528 83230 333 20/// 59008 83820=
63820 32580 20803 10305 20225 40130 82200 333 20262 59009 82823==
63135 NIL=
63742 12570 10507 10208 20148 48509 60014 81100 333 20155 59012 81820=

Upvotes: 1

Views: 77

Answers (1)

ikegami
ikegami

Reputation: 385789

my %map = (
   '/'   => '9',
   '333' => '33300',
   '555' => '55500',
   '='   => '',
);

my $pat = join '|', map quotemeta, keys(%map);
my $re = qr/($pat)/;

while (<>) {
   next if /NIL/;
   s/$re/$map{$1}/g;
   print;
}

The above works because the string matched is the key of the translation map. But you want to add the following:

s/^.*NIL.*\z//

There's no simple way to handle that generically. But we could handle that case specially.

my %map = (
   '/'   => '9',
   '333' => '33300',
   '555' => '55500',
   '='   => '',
);

my $pat = join '|', map quotemeta, keys(%map);
my $re = qr/^.*NIL.*\z|($pat)/;

while (<>) {
   s/$re/ defined($1) ? $map{$1} : "" /eg;
   print;
}

This is uglier, though possibly faster. Faster yet would be loading the entire file into memory.

my %map = (
   '/'   => '9',
   '333' => '33300',
   '555' => '55500',
   '='   => '',
   '=='  => '',
);

my $pat = join '|', map quotemeta, keys(%map);
my $re = qr/^.*NIL.*\n?|($pat)/m;

local $/;
while (<>) {
   s/$re/ defined($1) ? $map{$1} : "" /eg;
   print;
}

Upvotes: 2

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