POC for updating files as needed from an external source

find_changes.pl

#!/usr/bin/env perl
use strict;
use warnings;
use Digest::MD5;
use Cwd 'abs_path';
my $base_dir = './testdata/';
my $updates = 0;

# This is neater
sub hexdigest_file {
	open(my $fh, shift);
	binmode($fh);
	my $checksum = Digest::MD5->new->addfile(*$fh)->hexdigest;
	close($fh);
	return $checksum;
}

sub write_config {
	my($path, $entry) = @_;
	open(my $fh, '>' . $path);
	print $fh $entry->{'raw'};
	close($fh);

	# Check the checksum matches
	open(my $cfh, shift);
	binmode($cfh);
	my $new_checksum = Digest::MD5->new->addfile(*$cfh)->hexdigest;
	my $entry_checksum = $entry->{'checksum'};
	close($cfh);

	if($new_checksum ne $entry_checksum) {
		print "Checksum mismatch for $path\n";
	}
}

# This is temp - it would get pulled from the API really
my $api_data = {
	'data' => {
		'abc' => {
			'checksum' => "86fb269d190d2c85f6e0468ceca42a20",
			'raw' => "Hello world!",
		},
	},
};

print "Starting\n";
# Loop though the directory
opendir( my $dh, $base_dir );
foreach my $path ( readdir($dh) ) {
	# Deal with the special entries
	next if($path eq '.' || $path eq '..');

	# Make the path real
	$path = abs_path($base_dir.$path);

	# If this is a config file
	if( $path =~ /((.*)\/)?(.*)\.conf$/ ){
		my $file = $3;
		# $path - real path to file
		# $file - how we reference the file in the API

		# Check if this file needs deleting
		# Lets check this first - don't need to touch
		# the fs this way.
		if( !$api_data->{'data'}->{$file} ) {
			print "Should delete $path\n";
			unlink($path);
			$updates++;
			next;
		}

		# Check if we should update this file
		# This means stat'ing the fs but saves a lot of writes
		my $new_checksum = $api_data->{'data'}->{$file}->{'checksum'};
		my $current_checksum = hexdigest_file($path);
		if( $new_checksum ne $current_checksum ) {
			print "Should update $path\n";
			write_config($path, $api_data->{'data'}->{$file});
			$updates++;
			next;
		}

		print "$path looks all good\n";
	} else{
		print "$path should not exist - NOT A CONFIG FILE\n";
	}
}
closedir( $dh );

if($updates > 0) {
	print "Should call a reload here\n";
}
print "All done\n";