CODEWITHSUNDEEP
perl
sergio
sergio

Reputation: 31

Print whole line that begins with specific pattern

I have a text file that looks like this http://www.uniprot.org/uniprot/?sort=score&desc=&compress=no&query=id:P01375%20OR%20id:P04626%20OR%20id:P08238%20OR%20id:P06213&format=txt

I have to print only the lines in the text file that start with specific pattern (ID).

I tried it this way but it doesn't working:

open (IDS, 'example.txt') or die "Cannot open";    
my @ids = <IDS>;    
close IDS;    
my @IDS= "ID";    
foreach my $ids (@ids) {    
  if (my @ids =~ my @IDS){    
    print $ids;    
  } 
}

There probably must be some problem in this line **if (my @ids =~ my @IDS){.

If somebody can help me I would be very thankful.

Best

Upvotes: 0

Views: 1392

Answers (2)

Bala Krishnan
Bala Krishnan

Reputation: 374

After long list list of comments, here you go! This snippet works for both of your cases!

use strict;
use warnings;

open ( my $input, '<', 'printLinesStartingWithID.txt' ) or die $!; 
while ( <$input> ) { 
   if(/^ID/)
   {
        print "Matched line starting with ID: $_";
   }
   if(/^AC/)
   {
        my ($secondCol) = $_ =~ /^AC...(.*?)\;/;    #The three dots is to chop off the three empty spaces followed by 'AC'.
        print "Matched line starting with AC. The second column of the line is: $secondCol \n";
   }
}
close ( $input );

Upvotes: -1

Sobrique
Sobrique

Reputation: 53478

Your problem is almost certainly this line:

  if (my @ids =~ my @IDS){

because my is declaring a new variable, that 'hides' the one in the parent scope. Applying a regex match when both source and target are arrays is also going to behave in an odd sort of way - you're iterating @ids one element at a time, but then you're just matching the whole thing. And you're matching against another array, which ... actually works, but only because you're relying on casting the array to a string and back again.

It's also pretty bad style to have upper case and lower case variables of the same name, and you're doing it 3 times with @ids, @IDS, and IDS.

I'm also really not sure that my @IDS = "ID"; is doing what you think it's doing, and neither is trying to treat @IDS as a pattern in the first place.

Also - reading a file into an array then iterating it is less efficient that just iterating the file line by line.

Your code could probably be simplified as:

open ( my $input, '<', 'example.txt' ) or die $!; 
while ( <$input> ) { 
   print if m/ID/;
}
close ( $input );

Upvotes: 2

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