Unable to retrieve multiple column values from file in Perl - perl

Question

I have a file with following contents:
TIME
DATE TIME DAY
191227 055526 FRI
RC DEV SERVER
RC1 SERVER1
RC2 SERVER2
RC3 SERVER3
END
I am fetching argument values from this file, say if I pass DATE as an argument to the script I am getting corresponding value of the DATE. i.e., 191227
When I pass multiple arguments say DATE, DAY I should get values:
DATE=191227
DAY=FRI
But what I am getting here is:
DATE=191227
DAY=NULL
And if I pass RC as an argument I should get:
RC=RC1,RC2,RC3
The script looks below:
#!/usr/bin/perl
use strict;
use Data::Dumper;
print Dumper(\#ARGV);
foreach my $name(#ARGV){
print "NAME:$name\n";
my ($result, $start, $stop, $width) = "";
while(my $head = <STDIN>)
{
if( $head =~ (m/\b$name\b/g))
{
$start = (pos $head) - length($name);
$stop = (pos $head);
my $line = <STDIN>;
pos $head = $stop+1;
$head =~ (m/\b/g);
$width = (pos $head) - $start;
$result = substr($line,$start,$width);
}
}
$result =~ s/^\s*(.*?)\s*$/$1/;
print "$name=";
$result = "NULL" if ( $result eq "" );
print "$result\n";
}
Can someone please help me to get values if I pass multiple arguments also if suppose argument value have data in multiple lines it should be printed comma separated values (ex: for RC, RC=RC1,RC2,RC3).

Answer 1

Here is an example, assuming the input file is named file.txt and the values are starting at the same horizontal position as the keys:
package Main;
use feature qw(say);
use strict;
use warnings;
use Data::Dumper qw(Dumper);
my $self = Main->new(fn => 'file.txt', params => [#ARGV]);
$self->read_file();
$self->print_values();
sub read_file {
my ( $self ) = #_;
my $fn = $self->{fn};
open ( my $fh, '<', $fn ) or die "Could not open file '$fn': $!";
local $/ = ""; #Paragraph mode
my #blocks = <$fh>;
close $fh;
$self->{values} = {};
for my $block (#blocks) {
$self->parse_block( $block );
}
}
sub parse_block {
my ( $self, $block ) = #_;
my #lines = split /\n/, $block;
my $header = shift #lines;
my ($keys, $startpos) = $self->get_block_keys( $header );
for my $line ( #lines ) {
for my $key (#$keys) {
my $startpos = $startpos->{$key};
my $str = substr $line, $startpos;
my ( $value ) = $str =~ /^(\S+)/;
if ( defined $value ) {
push #{$self->{values}{$key}}, $value;
}
}
}
}
sub get_block_keys {
my ( $self, $header ) = #_;
my $values = $self->{values};
my #keys;
my %spos;
while ($header =~ /(\S+)/g) {
my $key = $1;
my $startpos = $-[1];
$spos{$key} = $startpos;
push #keys, $key;
}
for my $key (#keys) {
if ( !(exists $values->{$key}) ) {
$values->{$key} = [];
}
}
return (\#keys, \%spos);
}
sub new {
my ( $class, %args ) = #_;
return bless \%args, $class;
}
sub print_values {
my ( $self ) = #_;
my $values = $self->{values};
for my $key (#{$self->{params}}) {
my $value = "<NO VALUE FOUND>";
if ( exists $values->{$key} ) {
$value = join ",", #{$values->{$key}};
}
say "$key=$value";
}
}
Edit
If you want to read the file from STDIN instead, change the following part of the code:
# [...]
my $self = Main->new(params => [#ARGV]);
$self->read_file();
$self->print_values();
sub read_file {
my ( $self ) = #_;
local $/ = ""; #Paragraph mode
my #blocks = <STDIN>;
$self->{values} = {};
for my $block (#blocks) {
$self->parse_block( $block );
}
}
# [...]