how to update each line in a file

Question

i have file in that i have one line is like {<pN_SLOT>,<pN_Port>} ,user will give the value N for example N=9 ;then these lines should print 9 times in the file with increment of N value . Example: input file contains one line like this {<pN_SLOT>,<pN_Port>} then in output file it should update like this {<p0_SLOT>,<p0_Port>},{<p1_SLOT>,<p1_Port>},{<p2_SLOT>,<p2_Port>},...upto {<p8_SLOT>,<p8_Port>} . if any perl module please suggest any help/idea will be appreciable thank you

Answer 1

Something like this will do it:

#!/usr/bin/perl

use strict;
use warnings;

my $count = 9;
for my $num ( 0 .. $count ) {
    print "{<p${num}_SLOT>,<p${num}_Port>},\n";
}

If you're taking an input file, and wanting to replace 'N' with 'number', then what you need* is a regular expression:

#!/usr/bin/perl

use strict;
use warnings;

my $line = '{<pN_SLOT>,<pN_Port>}';
my $count = 9;
for my $num ( 0 .. $count ) {
    my $newline = ( $line =~ s/N/$num/gr ); 
    print "$newline\n";
}

The perlre page will give you some more regular expressions you can use to transform text.

As for reading in from files and numbers - this is actually the same problem. STDIN is a 'standard input' filehandle.

You can read from it with <STDIN>.

e.g.

print "Enter Number:\n"; 
my $response = <STDIN>; 
chomp ( $response ); #necessary, because otherwise it includes a linefeed. 

Or for reading from a file on disk:

open ( my $input_file, "<", "your_file_name" ) or die $!; 
my $line = <$input_file>;  #note - reads just ONE LINE here. 
chomp ( $line ); 
close ( $input_file ); 

If you want to read more than one line in the second example, you may want to look at perlvar and especially the $/ operator.

* need is strong - perl usually has many ways to do things. So in this case - "need" means "I suggest as a course of action".