regex problems

[cyphrix]

Hi guys. I'm very new to Perl. Making the switch from Python (cringe). The reason is because Perl seems to have much better regex capabilities than Python does and I need to really get started on this data extraction script my boss wants. However, I am finding it hard to do something that should be extremely simple. All I want to do is have the script open a simple text file, read it and as its reading do pattern matching. I can't seem to get it to open, read, and scan though. This was quite simple in (gulp) Python...please help

$file = open(INFILE, 'document.txt') or die;
if($file =~ /[+|-]user ID/)
{print "found User ID"}
else
{print "User ID not found"

Just something as simple as that...the code runs (using Perl Express IDE nice prog by the way) but it always returns false but I know for a fact that the pattern is a working pattern and I know that there are user id's in the text file. Any help is appreciated.

 

[ishnid]

Your "open" call isn't doing quite what you expect it to.

It opens the file "document.txt" for reading - so far so good. This creates a filehandle called INFILE, which is what you'll have to use to read contents from the file. The return value (which you're storing in $file) is merely true or false depending on whether your open was successful or not. Specifically, it doesn't put the contents of the file into $file.

For that reason, applying a regexp to $file won't do anything useful - you still need to read the contents of the file.

Normally, you'd try to avoid reading in the whole file at once (to save memory) and do *something* like this (depending on your requirements obviously):

open(INFILE, 'document.txt') or die;
while(<INFILE>) {
   if( /[+|-]user ID/ ) {
      print "found User ID";
      last;
   }
   elsif ( eof ) {
      print "User ID not found";
   }
}
close INFILE;

Of course you still can slurp the file into a single scalar if you really want to:

open(INFILE, 'document.txt') or die;
local $/;
my $file = <INFILE>;
if($file =~ /[+|-]user ID/) {
    print "found User ID";
}
else {
   print "User ID not found";
}
close INFILE;

 

[stevexff]

use strict;
use warnings;

open(INFILE, 'document.txt') or die $!;

while (<INFILE>) {
   print if /[+|-]user ID/;
}

close(INFILE);

As you have coded it the regex will match on "+user ID", "|user ID", or "-user ID" anywhere in the line. Is that what you want?

Steve

[small]"Every program can be reduced by one instruction, and every program has at least one bug. Therefore, any program can be reduced to one instruction which doesn't work." (Object:erlDesignPatterns)[/small]

 

[cyphrix]

Thanks very much to both of you for your help. I was able to get the file opened and read perfectly.