split (grep)

tbone654 has asked for the wisdom of the Perl Monks concerning the following question:

This is driving me crazy... I'm ultimately trying to read in two lists, one with a single column of ordered names... The second list is a column of names with a comma separated (this test script is using semi-colons) value after the name...
If I were able to do this in unix I would be:

grep -f file1 file2
[download]

Which is ok, but file1 loses it's order to file2, and what I really want to do is print values from file2 next to the order in file1... so I need to split off values and print the results next to the members of file1 where there is a match...
But it seems like today I'm too stupid to figure out how to do the split command correctly... Or, other... I could just print the line from list2, but there could be many values and I need to split them out to do math on them after I figure out the problem with split... perldoc -f split tells me it's returning the number of times each line succeeds, where I need to be able to manipulate the results. I've been searching the site for something similar, with no success. Thank you for any help in advance.

my $a;
my @foo = qw/tom steve bill roger bob/;
my @bar = qw/roger;99 steve;56 ted;88 tom;54/;
for($a=0;$a<@foo;$a++) {
        printf("%s %s\n",$foo[$a],grep(/$foo[$a]/,@bar));
        }
print "----\n";
for($a=0;$a<@foo;$a++) {
        # printf("%s\n", grep(/$foo[$a]/,@bar) );
        printf("%s\n", (split /;/, grep(/$foo[$a]/,@bar))[0] );
        }

--output before split--
tom tom;54
steve steve;56
bill
roger roger;99
bob
----
tom;54
steve;56

roger;99

--output using split--
tom tom;54
steve steve;56
bill
roger roger;99
bob
----
1
1
0
1
0
[download]

Comment on split (grep) Select or Download Code

Replies are listed 'Best First'.
Re: split (grep) by Laurent_R (Canon) on Oct 23, 2014 at 20:35 UTC
If your list is short, using `grep` on an array is fine. But this means that you are reading the whole array (second list) each time, which is quite inefficient if the list is long. In that case, using a hash for the second list is a better solution. Re-using toolic's data sample, it could look like this: `use warnings; use strict; my @foo = qw/tom steve bill roger bob/; my %bar = (roger => 99, steve => 56, ted => 88, tom => 54); for my $name (@foo) { print "$name : $bar{$name} \n" if exists $bar{$name}; }` [download] which prints: `tom : 54 steve : 56 roger : 99` [download] I understand that you are reading your data from files, so populating a hash is not more complicated than filling an array. You just have to do the split before populating the hash, instead of doing it later. Actually, even with a short list, I think that I would probably prefer the hash-based solution.	[reply] [d/l] [select]
Re^2: split (grep) by tbone654 (Beadle) on Oct 23, 2014 at 21:30 UTC
I understand why the hash-based solution makes more sense for performance. Especially in a "fancy" solution. I guess I just want to be able to split on the grep statement as an argument if I needed to... If I can... This started out as a one liner "brute force" grep replacement in case I needed more than a single or just a few members of the first list... `perl -ne 'next if(!/tom/ && !/steve/) ; printf("%10s %5s",(split/;/)[0 +,1]);' list.txt tom 54 steve 56` [download] Thank you for the input	[reply] [d/l]
Re^3: split (grep) by tbone654 (Beadle) on Oct 24, 2014 at 18:33 UTC
I settled on this for the moment, as it preserves the order of the first list, which is a requirement. `@foo = qw/tom steve bill roger bob/; @bar = qw/roger;99 steve;56 ted;88 tom;54/; foreach $line(@foo){ foreach $line1(@bar){ @split1=(split/;/,$line1); if($line =~ $split1[0]){ printf("%5s %3s\n",$split1[0],$split1[1]); } } } __END__ tom 54 steve 56 roger 99` [download] Thank you for the suggestions	[reply] [d/l]
Re: split (grep) by toolic (Bishop) on Oct 23, 2014 at 20:04 UTC
Tip #1 from the Basic debugging checklist: warnings `tom tom;54 steve steve;56 Missing argument in printf at ... bill roger roger;99 Missing argument in printf at ... bob ---- 1 1 0 1 0` [download] UPDATE: Is is this more like what you want? `use warnings; use strict; my @foo = qw/tom steve bill roger bob/; my @bar = qw/roger;99 steve;56 ted;88 tom;54/; for my $name (@foo) { my @match = grep { /$name/ } @bar; print "$name $match[0]\n" if @match; } __END__ tom tom;54 steve steve;56 roger roger;99` [download]	[reply] [d/l] [select]