ddrew78 has asked for the wisdom of the Perl Monks concerning the following question:

Monks, I am in need of your wisdom. I have 2 files, that look something like this: File 1 
aa-aa1-aa
aa-aa2-aa
aa-aa2-ab
aa-aa3-bc

[download]
File 2 
V1111:something
V1111:something
V2222:something
V1111:something

[download]
A third file will look like this: 
aa-aa1-aa
aa-aa2-ab

[download]
I need to search file 1 for matches to file 3, and then output the corresponding line from file 2. So with the example above, the output should show 
V1111:something
V2222:something

[download]
Essentially, if the first match in file 1 is on line 3, I need line 3 from file 2. I have no idea on how to match those values up to get the output I need. Thanks as always for any ideas.

Replies are listed 'Best First'.
Re: Match line number in different file
by LanX (Saint) on Jan 06, 2020 at 20:42 UTC

    • open file 1 and 2
    • read one line from each and build a $hash{line1}=line2
    • once done open file 3
    • output lines from $hash{line3}
    update

    in case 1 and 2 are very large and 3 is not, then do it the other way round:

    • read file 3 into a %seen hash
    • iterate again simultanously over 1 and 2
    • output lines seen in 3

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

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Re: Match line number in different file
by tybalt89 (Monsignor) on Jan 06, 2020 at 21:04 UTC 
    #!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11111080
use warnings;

my @file1 = split /^/, <<END;
aa-aa1-aa
aa-aa2-aa
aa-aa2-ab
aa-aa3-bc
END

my @file2 = split /^/, <<END;
V1111:something
V1111:something
V2222:something
V1111:something
END

my @file3 = split /^/, <<END;
aa-aa1-aa
aa-aa2-ab
END

my %one2two;
@one2two{@file1} = @file2;

print $one2two{$_} // '' for @file3;

    [download]
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Re: Match line number in different file
by poj (Abbot) on Jan 09, 2020 at 10:13 UTC
    if the first match in file 1

    Are the records in File1 and File3 unique or are there multiple lines with the same value like File2 ?

    poj
[reply]
      Files 1 and 3 only have unique values.
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Re: Match line number in different file
by Anonymous Monk on Jan 09, 2020 at 00:28 UTC
    Ummm ... "How Enormous" are these files?
[reply]
      These files are not very large, likely no more than about 200 lines.
[reply]

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