Perl replace string in file

Question

I am trying to prompt user to type input and replace certain attribute in a file with the input. This is not working. abc.txt contain line "NA" and I wish to replace with "user_input". Any help? Thanks

use strict;
use warnings;

my $x = "<process>NA</process>";
print "Please specify process used\n";
my $process = <STDIN>;
chomp $process;

open(XML, "<", "abc.txt") or die "Couldn't open file, $!";
while(<XML>){

    s/<process>NA</process>/<process>$process</process>/g;  
}

Answer 1

@Blurman, if you are using some sort of /bin/sh you use the inplace option of perl with this the one-liner:

echo -n 'process ? ';read p; perl -pi -e "s,<process>[^<]*</process>,<process>$p</process>,g" abc.txt

oh BTW, I changed NA w/ [^<]* to allow multiple consecutive runs;)

+Michel

Answer 2

The main part of your code is here:

open(XML, "<", "abc.txt") or die "Couldn't open file, $!";
while(<XML>){
  s/<process>NA</process>/<process>$process</process>/g;  
}

There are two main problems here that will stop your code doing what you want.

• You have / characters in side the match pattern and replacement string of your substitution operator. This means your code won't even compile. If you have / characters in your data, then the best option is to use a different character as the delimiter for the substitution operator.

   s|<process>NA</process>|<process>$process</process>|g;

• You change your data (which is stored in $_ ) but then you do nothing with the changed version. You need to write the changed version of the data back to a file.