Parsing for [] in a file

HJ has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks, I am kinda of a perl fumbler. I am stuck with a problem for more than an hour now, wish somebody cud give me pointers.

File1 :
a

File2 :
a|12
a[11]|1
a[11][11]|0
b|2
c|0

I want to pick only the variables from File2 that are in File1.

Output should hence be File3:
a|12
a[11]|1
a[11][11]|0

open FILE2, "$f2" or die "Could not open file: $! \n"; //Corrected >$f
+2
foreach my $var (keys %results) 
{ 
  while( my $attr_line=<FILE2>)
  {
    if($attr_line =~ m/(.*?)\[/ ) 
    { 
      if (exists $results{$1}) 
        {
             print $attr_line;
        } 
    }
  }
}
[download]

but my Output is
a|12

I even tried this and I see no output for this though( logical more sensible than the prev scrpt?

open FILE2, "$f2" or die "Could not open file: $! \n";
foreach my $var (keys %results) 
 { 
  while( my $attr_line=<FILE2>)
   {
     if($attr_line =~ /^\$var/ )
     { 
       print $attr_line;
       <strike>print $var."\n"; </strike>
     }
   }
 }
 
close(FILE2);
[download]

I understand the output is so because 'if exists' statement is true only for a|12. How do I make sure other any 'a*' be printed out too?

Thanks in advance, HJ

Comment on Parsing for [] in a file Select or Download Code

Replies are listed 'Best First'.
Re: Parsing for [] in a file by toolic (Bishop) on Nov 17, 2011 at 17:53 UTC
This gives you your desired output: `use warnings; use strict; my %results = (a => 1); foreach my $var (keys %results) { while (my $attr_line = <DATA>) { if ($attr_line =~ /^\Q$var/ ) { print $attr_line; } } } __DATA__ a\|12 a[11]\|1 a[11][11]\|0 b\|2 c\|0` [download] Update: in response to to OP's update, read http://sscce.org	[reply] [d/l]
Re^2: Parsing for [] in a file by MidLifeXis (Monsignor) on Nov 17, 2011 at 17:57 UTC
Except it will only work for the first key in %results, as the position in DATA will be at eof. If you flip around the `foreach` and the `while`, it should do as intended. Update: If you load the variable names (`%results`), make sure that you use chomp. --MidLifeXis	[reply] [d/l] [select]
Re^3: Parsing for [] in a file by HJ (Novice) on Nov 17, 2011 at 18:56 UTC
ah!that greatly worked. Thank you very much. swapping the foreach and while and chomping after foreach.	[reply]
Re^2: Parsing for [] in a file by HJ (Novice) on Nov 17, 2011 at 18:58 UTC
Hi toolic, Yes it worked just for the first line. Thanks for you response!	[reply]
Re: Parsing for [] in a file by JavaFan (Canon) on Nov 17, 2011 at 20:21 UTC
It seems that a shell one liner ought to do: `$ grep -f -F $file1 $file2 > $file3` [download]	[reply] [d/l]
Re: Parsing for [] in a file by Not_a_Number (Prior) on Nov 17, 2011 at 18:38 UTC
I even tried this and I see no output for this though Are you sure that File2 still contains the data that you think it does? If you ran the first version of your code on it, the line: `open FILE2, ">$f2" or die "Could not open file: $! \n";` opens a file for writing, not reading. In other words, it clobbers any existing data in the file...	[reply] [d/l]
Re^2: Parsing for [] in a file by HJ (Novice) on Nov 17, 2011 at 18:55 UTC
Apologize. Dint meant to have a ">$f2". Had it corrected before posting it. Thanks for the reply.	[reply]
Re: Parsing for [] in a file by aaron_baugher (Curate) on Nov 17, 2011 at 19:00 UTC
Open File1, read it line by line, parsing out the variables and saving them as the keys of a hash, with true values (like 1). Open File2, read it line by line, parsing out the variable at the beginning of the line, checking to see if that variable exists as a key in your hash, and printing the line if it does. Aaron B. My Woefully Neglected Blog, where I occasionally mention Perl.	[reply]
Re: Parsing for [] in a file by Marshall (Canon) on Nov 17, 2011 at 18:53 UTC
I even tried this and I see no output for this though( logical more sensible than the prev scrpt? if($attr_line =~ /^\$var/ ) should be if($attr_line =~ /^\Q$var/)	[reply]