CODEWITHSUNDEEP
perl
Yacob
Yacob

Reputation: 525

Perl to get a pattern from a file

I want to fetch values from file info.log and compare them to the string in $upper.

This what I tried

my $upper = "S14";

open(my $file,  "<",  "info.log")  or die "Can't open info.log: $!";

my $string = $upper;

while (<$file>)  {
  if ( ! -e $string) {
    print " print here $string\n";
  }
}

My file looks like this

ss1
ss2
ss3
ss4
ss5
ss6
ss7
ss8

the program outputs all the contents of the file. It should have not printed ss4 but it does?

Upvotes: 0

Views: 67

Answers (3)

Borodin
Borodin

Reputation: 126722

First of all, you must always start every Perl program with use strict and use warnings.

As other people have noted, the -e operator says whether a file of that name exists. It doesn't check whether one string appears witin another.

There are a few ways to do this. I would use a regular expression, but without knowing what sort of data you're dealing with, and to avoid confusing you, I have written a solution using the index function which returns zero or more if the second string appears within the first.

use strict;
use warnings

my $file = 'info.log';

my $upper = 'S14';

open my $fh, '<', $file  or die "Can't open '$file': $!";

my $string = $upper;

while (<$fh>)  {
  if (index($_, $string) >= 0) {
    print "This file contains '$string'\n";
    last;
  }
}

Upvotes: 1

Zach Leighton
Zach Leighton

Reputation: 1941

If you simply want to just search for the matches, use grep its faster. Otherwise iterate through with a foreach.

my $upper="S14";
open(my $file,  "<",  "info.log")  or die "Can't open info.log: $!";
my $string = $upper;
my @lines = <$file>;

my @matches grep { $_ =~ /$string/ } @lines; #searching *faster

foreach (@lines) { #iterating
   chomp; #new line stuff
   if($_ =~ /^$string$/is){
      #stuff
   }
}

Upvotes: -1

Jeef
Jeef

Reputation: 27265

The correct way to do this would be:

open (FILE, "< info.log") or die "error msg";
while (<FILE>)  
{
    if (/$upper/) {
        MATCH CASE
    }
}

Basically you loop through the file and check each line. Because you are reading the file in you don't need a variable ($_ is implied). on the check case.

Upvotes: 1

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