Push into end of hash in Perl - perl

Question

So what I am trying to do with the following code is push a string, let's say "this string" onto the end of each key in a hash. I'm completely stumped on how to do this. Here's my code:
use warnings;
use strict;
use File::Find;
my #name;
my $filename;
my $line;
my #severity = ();
my #files;
my #info = ();
my $key;
my %hoa;
my $xmlfile;
my $comment;
my #comments;
open( OUTPUT, "> $ARGV[0]" );
my $dir = 'c:/programs/TEST/Test';
while ( defined( $input = glob( $dir . "\\*.txt" ) ) ) {
open( INPUT, "< $input" );
while (<INPUT>) {
chomp;
if (/File/) {
my #line = split /:/;
$key = $line[1];
push #{ $hoa{$key} }, "Filename\n";
}
if ( /XML/ ... /File/ ) {
$xmlfile = $1;
push #{ $hoa{$key} }, "XML file is $xmlfile\n";
}
if (/Important/) {
push #{ $hoa{$key} }, "Severity is $_\n";
}
if (/^\D/) {
next if /Important/;
push #{ $hoa{$key} }, "Given comment is $_\n";
}
push #{ $hoa{$key} }, "this string\n";
}
}
foreach my $k ( keys %hoa ) {
my #list = #{ $hoa{$k} };
foreach my $l (#list) {
print OUTPUT $l, "\n";
}
}
}
close INPUT;
close OUTPUT;
Where I have "this string" is where I was trying to push that string onto the end of the array. However, what ended up happening was that it ended up printing "this string" three times, and not at the end of every key like I wanted. When I tried to put it outside the while() loop, it said that the value of $key was not initialized. So please, any help? And if you need any clarification on what I'm asking, just let me know. Thank you!

Answer 1

No offence, but there are so many issues in this code I don't even know where to start...
First, the 'initialization block' (all these my $something; my #somethings lines at the beginning of this script) is not required in Perl. In fact, it's not just 'redundant' - it's actually confusing: I had to move my focus back and forth every time I encountered a new variable just to check its type. Besides, even with all this $input var is still not declared as local; it's either missing in comments, or the code given has omissions.
Second, why do you declare your intention to use File::Find (good) - but then do not use it at all? It could greatly simplify all this while(glob) { while(<FH>) { ... } } routine.
Third, I'm not sure why you assign something to $key only when the line read is matched by /File/ - but then use its value as a key in all the other cases. Is this an attempt to read the file organized in sections? Then it can be done a bit more simple, either by slurp/splitting or localizing $/ variable...
Anyway, the point is that if the first line of the file scanned is not matched by /File/, the previous (i.e., from the previous file!) value is used - and I'm not quite sure that it's intended. And if the very first line of the first file is not /File/-matched, then an empty string is used as a key - again, it smells like a bug...
Could you please describe your task in more details? Give some test input/output results, perhaps... It'd be great to proceed in short tasks, organizing your code in process.

Answer 2

Your program is ill-conceived and breaks a lot of good practice rules. Rather than enumerate them all, here is an equivalent program with a better structure.
I wonder if you are aware that all of the if statements will be tested and possibly executed? Perhaps you need to make use of elsif?
Aside from the possibility that $key is undefined when it is used, you are also setting $xmlfile to $1 which will never be defined as there are no captures in any of your regular expressions.
It is impossible to tell from your code what you are trying to do, so we can help you only if you show us your output, input and say how to derive one from the other.
use strict;
use warnings;
use File::Find;
my ($outfile) = #ARGV;
my $dir = 'c:/programs/TEST/Test';
my %hoa;
my $key;
while (my $input = glob "$dir/*.txt") {
open my $in, '<', $input or die $!;
while (<$in>) {
chomp;
if (/File/) {
my $key = (split /:/)[1];
push #{ $hoa{$key} }, "Filename\n";
}
if (/XML/ ... /File/) {
my $xmlfile = $1;
push #{ $hoa{$key} }, "XML file is $xmlfile\n";
}
if (/Important/) {
push #{ $hoa{$key} }, "Severity is $_\n";
}
if (/^\D/) {
next if /Important/;
push #{ $hoa{$key} }, "Given comment is $_\n";
}
push #{ $hoa{$key} }, "this string\n";
}
close $in;
}
open my $out, '>', $outfile or die $!;
foreach my $k (keys %hoa) {
foreach my $l (#{ $hoa{$k} }) {
print $out $l, "\n";
}
}
close $out;

Answer 3

I suspect based on your code, that the line where $key is set is not called each time through the loop, and that you do not trigger any of the other if statements.
This would append "this string" to the end of the array. Based on that you are getting 3 of the "this strings" at the end of the array, I would suspect that two lines do not go through the if (/FILE/) or any of the other if statements. This would leave the $key value the same and at the end, you would append "this string" to the array, using whatever the last value of $key was when it was set.

Answer 4

This will append the string "this string" to every element of the hash %hoa, which elements are array refs:
for (values(%hoa)) { push #{$_}, "this string"; }
Put that outside your while loop, and you'll print "this string" at the end of each element of %hoa.
It will autovivify array refs where it finds undefined elements. It will also choke if it cannot dereference an element as an array, and will manipulate arrays by symbolic reference if it finds a simple scalar and is not running under strict:
my %autoviv = ( a => ['foo'], b => undef );
push #$_, "PUSH" for values %autoviv; # ( a => ['foo', 'PUSH'], b => ['PUSH'] )
my %fatal = ( a => {} );
push #$_, "PUSH" for values %fatal; # FATAL: "Not an ARRAY reference at..."
my %dangerous = (a => "foo");
push #$_, "PUSH" for values %dangerous; # Yikes! #foo is now ("PUSH")
use strict;
my %kablam = (a => "foo");
push #$_, "PUSH" for values %kablam; # "Can't use string ("foo") as an ARRAY ref ..."

Answer 5

As I understand it, traverse the hash with a map command to modify its keys. An example:
EDIT: I've edited because I realised that the map command can be assigned to the same hash. No need to create a new one.
#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
my %hash = qw|
key1 value1
key2 value2
key3 value3
|;
my %hash = map { $_ . "this string" => $hash{ $_ } } keys %hash;
print Dump \%hash;
Run it like:
perl script.pl
With following output:
$VAR1 = {
'key3this string' => 'value3',
'key2this string' => 'value2',
'key1this string' => 'value1'
};