Regular Expression matching in PERL

Legend986 · #1 (**permalink**) 02-26-2008

I am trying to read a file and capture particular lines into different strings:

Code:

LENGTH: Some Content here

TEXT: Some Content Here

COMMENT: Some Content Here

I want to be able to get (LENGTH: .... ) into one array and so on... I'm trying to use PERL in slurp mode but for some reason I'm having trouble. Can someone suggest me a better way?

Yogesh Sawant · #2 (**permalink**) 02-26-2008

instead of slurping the whole file in one array and then filtering out the lines, run a loop over the file and read one line at a time. here yoy can put the lines in respective arrays as per the category, with the help of regex
something like this would help you:

Code:

while (<>) {
    if (m/^\s*LENGTH:\s*/) {
        push (@length_array, $_);
    }
    elsif (m/^\s*TEXT:\s*/) {
        push (@text_array, $_);
    }
    elsif (m/^\s*COMMENT:\s*/) {
        push (@comment_array, $_);
    }
}

Legend986 · #3 (**permalink**) 02-26-2008

Thanks. Well, I have done that in my php version of the same code but heard that perl is really strong when it comes to regex so wanted to try out something new. Actually the problem is something like this:

Code:

LENGTH: ......................................................
..................................................................
..................................................................

...................................................................
..................................................................

SUBJECT: .......................................................

COMMENT: .....................................................
....................................................................

As you can observe, the data that I want is not limited to one line but rather spans multiple lines. Do you have any suggestion on how to solve this problem?

Yogesh Sawant · #4 (**permalink**) 02-26-2008

the code that i posted above won't work, since what you want is something like a multi-line regex

Legend986 · #5 (**permalink**) 02-26-2008

Yes. Incidentally, my php version was almost similar to what you posted but I was just hoping there was a multi line solution to the problem. Do you have any suggestions please?

Yogesh Sawant · #6 (**permalink**) 02-26-2008

check if this works for you:

Code:

{
    local $/;  # reset the input record separator
    $all_lines = <INPUT_FILE>;  # Slurp the whole file in a string
}
while ($all_lines =~ m/LENGTH:(.*?)(SUBJECT|COMMENT)/g) {
    push (@length_array, $1);
}
while ($all_lines =~ m/SUBJECT:(.*?)(LENGTH|COMMENT)/g) {
    push (@subject_array, $1);
}
while ($all_lines =~ m/COMMENT:(.*?)(LENGTH|SUBJECT)/g) {
    push (@comment_array, $1);
}

idea is to slurp the file in a string instead of in an array, and then take out the required strings from it using regex

Legend986 · #7 (**permalink**) 02-26-2008

Actually I was doing something on a similar lines:

Code:

$capture[0] = "LENGTH:";
$capture[1] = "COMMENT:";
$capture[2] = "BODY:";
$capture[3] = "AVATAR:";
$capture[4] = "POST:";
$capture[5] = "SUBJECT:";
$capture[6] = "DATE:";
$capture[7] = ""; 

open(DATA, "filename.txt");
$line = <DATA>;


if($line =~ /$capture[0](.*?)$capture[1]/sgm) {
        $solution[0] = $1;
}
if($line =~ /$capture[1](.*?)$capture[2]/sgm) {
        $solution[1] = $1;
}
if($line =~ /$capture[2](.*?)$capture[3]/sgm) {
        $solution[2] = $1;
        }
        if($line =~ /$capture[3](.*?)$capture[4]/sgm) {
                $solution[3] = $1;
        }
        if($line =~ /$capture[4](.*?)$capture[5]/sgm) {
                $solution[4] = $1;
        }
        if($line =~ /$capture[5](.*?)$capture[6]/sgm) {
                $solution[5] = $1;
        }
if($line =~ /$capture[6](.*?)$capture[7]/sgm) {
                $solution[6] = $1;
        }


print trim($solution[0])."\n";
print trim($solution[1])."\n";
print trim($solution[2])."\n";
print trim($solution[3])."\n";
print trim($solution[4])."\n";
print trim($solution[5])."\n";
print trim($solution[6])."\n";

For some reason, it prints only the odd number of lines or even number of lines depending on how the ordering is. Well, I see why that is happening but not sure how to solve it... Anyways I will try to incorporate your logic now...

EDIT: Well, works like a charm if I embed your logic into mine

I just changed the if into a while... Great! Thanks a lot for your help...

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