Trying to read a file into a Hash of Arrays

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

Hi Monks,

I'm trying to read a datafile and append data onto a specific line as indexed/identified by the first word.

The data file is in this format

name,success1,description1,success2,description2,...

eg:

dog,yes,string1,yes,string2
cat,no,string3
mouse,no,string4,no,string5
horse
ferret
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My attempt at doing this is below. Apart from it not working, it seems to hang on the 'split' line

#!/bin/perl
use strict;
use warnings;
use Data::Dumper;
my $name="mouse";
open (FH, "datafile.txt")||die "cannot open file";
while ( <FH> ) { 
   next unless s/^(.*?):\s*//;
   $HoA{$1} = [ split /,/ ];
 }
print Dumper(%HoA);
my $success="yes";
my $description="new string";
push @{ $HoA{$name} }, $success, $description;
for $venue ( keys %HoA ) {
   print FH "$venue @{ $HoA{$venue} }\n";
}
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Can any one help and show me the correct way, or even a better way, of doing this??

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Re: Trying to read a file into a Hash of Arrays
by Athanasius (Archbishop) on Feb 20, 2015 at 04:46 UTC

This doesn’t even compile. You have use strict but then don’t declare %HoA or $venue.

it seems to hang on the 'split' line

No, even if you get it to run, it never reaches the split line: the preceding line:

next unless s/^(.*?):\s*//;
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skips all the input lines, because none of them contain a colon as specified in the regex.

Also note that you cannot write to a filehandle which has been opened for reading only. See:

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re: Trying to read a file into a Hash of Arrays
by vinoth.ree (Monsignor) on Feb 20, 2015 at 04:46 UTC

You have opened a file for reading input but, you are trying to write into it.

Filehandle FH opened only for input at pl.pl line 18, <FH> line 5

Open the file in read/write mode as below,

#!/bin/perl
use strict;
use warnings;
use Data::Dumper;
my $name="mouse";
pen (FH, "+<","datafile.txt")||die "cannot open file";
my (%HoA,$venue);
while ( <FH> ) {
   next unless s/^(.*?):\s*//;
   $HoA{$1} = [ split /,/ ];
 }
print Dumper(%HoA);
my $success="yes";
my $description="new string";
push @{ $HoA{$name} }, $success, $description;
for $venue ( keys %HoA ) {
   print FH "$venue @{ $HoA{$venue} }\n";
}
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Update:
++Athanasius,Missed use strict; part.

All is well. I learn by answering your questions...

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Re: Trying to read a file into a Hash of Arrays
by LanX (Saint) on Feb 20, 2015 at 04:46 UTC

> next unless s/^(.*?):\s*//;

Please explain what this line is supposed to do in "your attempt".

Cheers Rolf

PS: Je suis Charlie!

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Re: Trying to read a file into a Hash of Arrays
by sandy105 (Scribe) on Feb 20, 2015 at 10:42 UTC

yes that is correct it will skip all lines because your test data signature does not have : or else your actual test data looks like "dog: string1,str2...."

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Re^2: Trying to read a file into a Hash of Arrays

by LanX (Saint) on Feb 20, 2015 at 15:42 UTC

> actual test data ..

Well the actual test data included $venue as keys...

Most likely C&P homework...

Cheers Rolf

PS: Je suis Charlie!

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