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

Hi all, I need to match the contents of file against another. 
file1:
1
2
3

file2:
55  1
65  2
76  3

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if the contents of file1 match a column of data in file 2 printout to a new file the entire line whith mtached data. I have tried putting both files into an array and then use foreach to search, but having problems (naturally) 

open (file, "<file1");
while (<file>) {
@array=$_;
}

open (file2, "<file2");
open (out, ">out");
while (<file2>) {
@array2=$_;
($one, $two) = split (/\s+/, $_);
                }

foreach $file2 (@array2) {
foreach $file1 (@array) {

###lost here

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thanks

Replies are listed 'Best First'.
Re: matching an array
by dragonchild (Archbishop) on Jul 19, 2004 at 19:41 UTC
    • Is it going to match a specific column in the second file?
    • Does row #1 in file1 have to match row #1 in file2? What if row1 doesn't, but all other rows do?
    • Do you need to preserve the line for matches in file2? What I mean is if lines 1, 3, & 5 match, do you just have to say that or do you have to display the whole line for whom a column matched?

    You might know what you're trying to do, but you're not explaining it very well. The more detail, the better the help.

    ------
    We are the carpenters and bricklayers of the Information Age.

    Then there are Damian modules.... *sigh* ... that's not about being less-lazy -- that's about being on some really good drugs -- you know, there is no spoon. - flyingmoose

    I shouldn't have to say this, but any code, unless otherwise stated, is untested

[reply]
      just need to compare against column two in file2. Then print the whole line if column 2 mtaches file1.
[reply]
        So, can line9 in file1 match the value on line3 in file2? What happens if the number of lines are different? You're not thinking of the various possibilities that a piece of code should really take into account.

        ------
        We are the carpenters and bricklayers of the Information Age.

        Then there are Damian modules.... *sigh* ... that's not about being less-lazy -- that's about being on some really good drugs -- you know, there is no spoon. - flyingmoose

        I shouldn't have to say this, but any code, unless otherwise stated, is untested

[reply]
Re: matching an array
by davorg (Chancellor) on Jul 19, 2004 at 20:07 UTC

    It's not very clear exactly what your program needs to do, but I think you want something a bit like this.

    open FILE1, 'file1' or die $!;
my @keys = <FILE1>;
chomp @keys;
my %keys = map { $_ => 1 } @keys;
close FILE1;

open FILE2, 'file2' or die $!;
open FILE3, '>file3' or die $!; # output file

print FILE3 grep { exists $keys{(split)[1]} } <FILE2>;

close FILE2;
close FILE3;

    [download]
    --
    <http://www.dave.org.uk>

    "The first rule of Perl club is you do not talk about Perl club."
    -- Chip Salzenberg

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[d/l]
Re: matching an array
by graff (Chancellor) on Jul 20, 2004 at 03:08 UTC
    I find myself having to do this sort of thing a lot with various pairs of files; usually the column delimiters are whitespace (like your case) and sometimes they are other things (colons, commas, or whatever); usually the "key" field is in the first column and sometimes it's elsewhere; usually I just need to see keys that make up the intersection (or union or difference) and sometimes I want to see the whole line from one file or the other or both.

    So I wrote a general purpose utility to handle all that, and I use it almost every day. I posted it here: cmpcol

    For your case, the command line would be: 

     cmpcol -i -l2 file1 file2:2 > file3

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    i.e.: show the intersection (-i), list full lines from the second file (-l2), compare the first column in file1 (default key field) against the second column in file2 (:2), redirect stdout to file3. HTH
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[d/l]
Re: matching an array
by pbeckingham (Parson) on Jul 19, 2004 at 19:44 UTC

    Try using List:Util to compare lists.

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