Perl hash formatting - perl

Question

I have a log file like below
ID: COM-1234
Program: Swimming
Name: John Doe
Description: Joined on July 1st
------------------------------ID: COM-2345
Program: Swimming
Name: Brock sen
Description: Joined on July 1st
------------------------------ID: COM-9876
Program: Swimming
Name: johny boy
Description: Joined on July 1st
------------------------------ID: COM-9090
Program: Running
Name: justin kim
Description: Good Record
------------------------------
and I want to group it based on the Program (Swimming , Running etc) and want a display like,
PROGRAM: Swimming
==>ID
COM-1234
COM-2345
COM-9876
PROGRAM: Running
==>ID
COM-9090
I'm very new to Perl and I wrote the below piece (incomplete).
#!/usr/bin/perl
use Data::Dumper;
$/ = "%%%%";
open( AFILE, "D:\\mine\\out.txt");
while (<AFILE>)
{
#temp = split(/-{20,}/, $_);
}
close (AFILE);
my %hash = #new;
print Dumper(\%hash);
I have read from perl tutorials that hash key-value pairs will take unique keys with multiple values but not sure how to make use of it.
I'm able to read a file and store in to hash, unsure how to process to the aforementioned format.Any help is really appreciated.Thanks.

Answer 1

I always prefer to write programs like this so they read from STDIN as that makes them more flexible.
I'd do it like this:
#!/usr/bin/perl
use strict;
use warnings;
use 5.010;
# Read one "chunk" of data at a time
local $/ = '------------------------------';
# A hash to store our results.
my %program;
# While there's data on STDIN...
while (<>) {
# Remove the end of record marker
chomp;
# Skip any empty records
# (i.e. ones with no printable characters)
next unless /\S/;
# Extract the information that we want with a regex
my ($id, $program) = /ID: (.+?)\n.*Program: (.+?)\n/s;
# Build a hash of arrays containing our data
push #{$program{$program}}, $id;
}
# Now we have all the data we need, so let's display it.
# Keys in %program are the program names
foreach my $p (keys %program) {
say "PROGRAM: $p\n==>ID";
# $program{$p} is a reference to an array of IDs
say "\t$_" for #{$program{$p}};
say '';
}
Assuming this is in a program called programs.pl and the input data is in programs.txt, then you'd run it like this:
C:/> programs.pl < programs.txt

Answer 2

Always put use warnings; and use strict; in top of the program. And always use three argument for open
open my $fh, "<", "D:\\mine\\out.txt";
my %hash;
while (<$fh>){
if(/ID/)
{
my $nxt = <$fh>;
s/.*?ID: //g;
$hash{"$nxt==>ID \n"}.=" $_";
}
}
print %hash;
Output
Program: Running
==>ID
COM-9090
Program: Swimming
==>ID
COM-1234
COM-2345
COM-9876
I your input file program were found at the line after ID. So I used
my $nxt = <$fh>; Now the program were store into the $nxt variable.

Answer 3

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my %hash = ();
open my $IN, "<", "your file name here" or die "Error: $!\n";
while (<$IN>) {
if ($_ =~ m/^\s*-*ID:\s*COM/) {
(my $id) = ($_ =~ m/\s*ID:\s*(.*)/);
my $prog_name = <$IN>;
chomp $prog_name;
$prog_name =~ s/Program/PROGRAM/;
$hash{$prog_name} = [] unless $hash{$prog_name};
push #{$hash{$prog_name}}, $id;
}
}
close $IN;
print Dumper(\%hash);
Output will be:
$VAR1 = {
'PROGRAM: Running' => [
'COM-9090'
],
'PROGRAM: Swimming' => [
'COM-1234',
'COM-2345',
'COM-9876'
]
};
Let's look at these two lines:
$hash{$prog_name} = [] unless $hash{$prog_name};
push #{$hash{$prog_name}}, $id;
The first line initiates an empty array reference as the value if the hash is undefined. The second line pushes the ID to the end of that array (regardless of the first line).
Moreover, the first line is not mandatory. Perl knows what you mean if you just write push #{$hash{$prog_name}}, $id; and interprets it as if you said "go to the value of this key" and creates it if it wasn't already there. Now you say that the value is an array and you push $id to the list.