perl - replace every nth (and multiples) occurrences of a character with another character

Question

Does anyone know any unix commands/perl script that would insert a specific character (that can be entered as either hex (ie 7C) or as the actual character (ie |)) in the po

Answer 1

Small perl hack to solve the problem. Using the index function to find the commas, modulus to replace the right one, and substr to perform the replacement.

use strict;
use warnings;

while (<>) {
    my $x=index($_,","); 
    my $i = 0; 
    while ($x != -1) {
        $i++; 
        unless ($i % 3) { 
            $_ = substr($_,0,$x) ."|". substr($_,$x+1); 
        }
        $x = index($_,",",$x + 1) 
    } 
    print;
}

Run with perl script.pl file.csv.

Note: You can place the declaration my $i before the while(<>) loop in order to do a global count, instead of a separate count for each line. Not quite sure I understood your question in that regard.