CODEWITHSUNDEEP
perl
Naidu
Naidu

Reputation: 149

how to read a string from one file and check wether that string is in another file using perl

I have two text files. One file with some data like

 hi 
 how

and another file like 

L_ hello hi whats up
 N_ david
 N_ jhon
 N_ abraham
 N_ mc D  
L_ hey how u doing
 N_ david
 N_ jhon
 N_ abraham
 N_ mc D
L_ some blah blah blah
 N_ david
 N_ jhon
 N_ abraham
 N_ mc D

How can I take a line from the first file and check for presence of this line in the other file?

If the line is present (e.g. hi in my example) I need to print only that search string and the names just below that line. Consider L_ is some identifier for line where we check for the string if the string is present in that line I want to print the name just below that line with identifier N_ and not the other ones, while printing the identifiers L_ and N_ should be removed.

I am looking for advice on how to solve this using Perl.

Upvotes: 0

Views: 112

Answers (3)

mpapec
mpapec

Reputation: 50637

perl -ne'
  BEGIN{
  $x = pop;
  ($re) = map qr/$_/, join "|", map /(\w+)/ && qr/\Q$1/, <>;
  @ARGV = $x;
  }
  $b = /($re)/ and print("\n$1"),next if /^L_/;
  chomp; s/^\w+_//;
  print if $b
' file1 file2

output

hi david jhon abraham mc D
how david jhon abraham mc D

Upvotes: 1

Sobrique
Sobrique

Reputation: 53478

You probably want to be looking at the perl functions open and grep. 

    my $datafile = "some_data_file.txt";
    my $comparefile = "data_to_compare.txt";
    open ( my $data_filehandle, "<", $datafile ) or die $!;
    my @things_to_find = <$data_filehandle>;

    open ( my $compare_filehandle, "<", $comparefile ) or die $!;
    while ( my $line = <$compare_filehandle> ) 
    {
       foreach my $thing ( @things_to_find )
       {
          print "Match found with: $line" if $line =~ m/$thing/;
          print "Next line is :", <$compare_filehandle>;
       }
    }

That'll pull out the lines that match the pattern, and then print the following line. I'll leave you to figure out the details of parsing each line. The perl documentation on perlre will help you here.

Upvotes: 0

Lee Duhem
Lee Duhem

Reputation: 15121

Try this one:

#!/usr/bin/perl

use strict;
use warnings;

open my $patterns, '<', "$ARGV[0]"
    or die "Cannot open $ARGV[0]:$!";
open my $data, '<', "$ARGV[1]"
    or die "Cannot open $ARGV[1]:$!";

my @patterns;
while (<$patterns>) {
    chomp;
    push @patterns, $_;
}

my $line;
LINE: while ($line = <$data>) {
    chomp $line;
    if ($line =~ m/^\s*L_/) {
        foreach my $pat (@patterns) {
            if ($line =~ m/$pat/) {
                print "$line\n";
                while ($line = <$data>) {
                    if ($line =~ m/^\s*N_/) {
                        print $line;
                    }
                    else {
                        redo LINE;
                    }
                }
            }
        }
    }
}

Upvotes: 0

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