perl write variables to a file - perl

Question

Here's my code to parse a configuration file, write the retrieved data to another file and send it to a MySQL database.
The database connection and writing data to a table works fine, however I can't get it to write data to the mentioned file mongoData.txt.
I'm quite new to Perl, so any help will be highly appreciated.
#!/usr/bin/perl
use strict;
use warnings;
use DBI;
my $line;
# Retrieving data
open( my $FILE, "<", "/etc/mongod.conf" )
or die "Cannot find file! : $!\n";
while ( $line = <$FILE> ) {
chomp($line);
my ( $KEY, $VALUE ) = split /\:/, $line;
# Ignoring commented lines
$_ = $line;
unless ( $_ = ~/^#/ ) {
# Write to file
open my $FILE2, ">", "/home/sierra/Documents/mongoData.txt"
or die "Cannot create file $!\n";
print $FILE2 "$KEY", "$VALUE\n";
}
# Connection to SQL database
my $db = DBI->connect(( "dbi:mysql:dbname=mongodconf;
host = localhost;", "root", "sqladmin"
)) or die "can't connect to mysql";
# Inserting into database
$db->do("insert into data values ('$KEY', '$VALUE')")
or die "query error\n";
}
close($FILE);

Answer 1

Every time you open a file for output, you create a new file and delete any pre-existing file with the same name. That means you're going to be left with only the last line you wrote to the file
Here are some more pointers
Variable identifiers should in general be all in digits, lower case letters, and underscores. Capital letters are reserved for global identifiers such as package names
If you are running a version of Perl later than v5.14 then you can use autodie which checks all IO operations for you and removes the need to test the return status by hand
If you use a die string that has no newline at the end, then Perl will add information about the source file name and line number where it occurred, which can be useful for debugging
It is unnecessary to name your loop control variables. Programs can be made much more concise and readable by using Perl's pronoun variable $_ which is the default for many built-in operators
It is wasteful to reconnect to your database every time you need to make changes. You should connect once at the top of your program and use that static connection throughout your code
You should use placeholders when passing parameter expressions to an SQL operation. It can be dangerous, and that way DBI will quote them correctly for you
There is no need to close input files explicitly. Everything will be closed automatically at the end of the program. But if you are worried about the integrity of your output data, you may want to do an explicit close on output file handles so that you can check that they succeeded
Here's what I would write. Rather than testing whether each line of the input begins with a hash, it removes everything from the first hash character onwards and then checks to see if there are any non-blank characters in what remains. That allows for trailing comments in the data
#!/usr/bin/perl
use strict;
use warnings 'all';
use autodie;
use DBI;
my ($input, $output, $dsn) = qw{
/etc/mongod.conf
/home/sierra/Documents/mongoData.txt
dbi:mysql:dbname=mongodconf;host=localhost;
};
open my $fh, '<', $input;
open my $out_fh, '>', $output;
my $dbh = DBI->connect($dsn, qw/ root sqladmin /)
or die "Can't connect to MySQL: $DBI::errstr";
while ( <$fh> ) {
chomp;
s/#.*//;
next unless /\S/;
my ( $key, $val ) = split /\:/;
print $out_fh "$key $val\n";
$dbh->do('insert into data values (?, ?)', $key, $val);
}
close $out_fh or die $!;
$dbh->disconnect or warn $dbh->errstr;

Answer 2

You need to append the text into the creating new file mongoData.txt
while ($line=<$FILE>)
{
chomp ($line);
my ($KEY, $VALUE) = split /\:/,$line;
# Ignoring commented lines
$_ = $line;
unless ($_ = ~/^#/)
{
open my $FILE2, ">>", "/home/sierra/Documents/mongoData.txt" or die "Cannot create file $!\n";
print $FILE2 "$KEY","$VALUE\n";
}
}
close($FILE2);
or else
Create the text file once before your nesting the while loop
open my $FILE2, ">", "/home/sierra/Documents/mongoData.txt"
or die "Cannot create file $!\n";
while ($line=<$FILE>)
{
chomp ($line);
my ($KEY, $VALUE) = split /\:/,$line;
# Ignoring commented lines
$_ = $line;
unless ($_ = ~/^#/)
{
print $FILE2 "$KEY","$VALUE\n";
}
}
close($FILE2);
May be this will help you.