I am new in perl, and I need to connect the database use DBI. My code as follows:
use LWP::Simple;
use XML::Simple qw(:strict);
use Data::Dumper;
use DBI;
use Getopt::Long;
use IO::Uncompress::Gunzip qw(gunzip $GunzipError);
use IO::File;
use warnings;
$dbh = DBI->connect("dbi:);
if (!$dbh) {
&logMsg(0, "$DBI::errstr");
die;
} else {&logMsg(0,"Connection to $dbName DB OK")}
I already set the values. Its kind like connection failed, but I didn't get any errors. I also check the log file, there is nothing showing. What can I do for checking the errors? Thanks for any comments and help.
I can't find anything wrong with your code, unless logMsg just doesn't work, but it's a tedious way to go about using DBI.
Rather than checking if something went wrong with DBI, it's much better to set DBI to throw an error. You can do this with RaiseError.
my $dbh = DBI->connect(
"dbi:ODBC:DSN=$dbName;Server=$dbHost",
$dbUser, $dbPassword,
{ RaiseError => 1 }
);
Now if DBI has a failure, including trying to connect, it will throw an error and stop the program. This avoids having to check for an error every time you use the database (you'll forget).
DBI;
$dbh = DBI->connect('Your_Database_Name', 'user_id','Password');
my $sth = $dbh->prepare ("select * from Table_name");
$sth->execute();
my #row_ary = $sth->hetshrow_array;
foreach $item (#row_ary)
{
print "$item\n";
}
Related
I am trying to connect to Hive via Perl module Thrift::API::HiveClient and below is the code to connect to Hadoop hive and retrieve the data
#!/usr/bin/perl
use DBI;
use DBI::DBD;
use Data::Dumper;
use List::MoreUtils qw(uniq);
use DateTime;
#use warnings 'all';
use POSIX qw(strftime);
use LWP::Simple;
use Thrift;
use Thrift::API::HiveClient;
use Data::Dumper;
my $latest_return;
# Database connection
my $client = Thrift::API::HiveClient->new(
host => 'localhost',
port => '10000',
);
$client->connect or die "Could not connect";
my $rh = $client->execute('select * from devtest.users');
my $return = [];
while ($latest_return = $client->fetch($rh)) { # will die with an error if it fails
print $latest_return;
}
When I execute the above script it throws below message
Thrift::TException=HASH(0x25d18e0)
I also tried Dumper to print the result nothing got printed.
any help is much appreciated.
OK, so the problem here is - you're doing something that's failing.
The module you import - Thrift::API::Hiveclient warns:
THIS CODE IS ALPHA-QUALITY, EXPERIMENTAL, AND LIKELY FLAMMABLE
Having said that - what is happening here, is for some the action is failing, and it's dieing with an error object.
That error object has status code and message with it. (I don't think this is idomatic perl though, it's more like Java :)).
So in the connect there's an error, that's not being handled properly so your code is dying.
A Thrift::TException is a fairly simple sort of object:
package Thrift::TException;
sub new {
my $classname = shift;
my $self = {message => shift, code => shift || 0};
return bless($self,$classname);
}
1;
Literally just a message and a code.
To get at that message, you'll need to dereference your object, and that's what doesn't seem to be happening.
My best guess is the _open method in Thrift::Socket is returning an error, and the HiveClient isn't actually trapping/handling it.
It should be doing an eval and trapping the error, and then unpacking the TException.
Somewhere here:
sub connect {
my ($self) = #_;
$self->_transport->open;
}
Maybe. I'm not 100% sure, because Moo might do something cute with die, but I can't find or see where that is.
So short answer - you're probably failing to connect, to be sure you'd need to grab that error message - to do that you'll need to hack the Hiveclient to eval the operation. This is what you signed up for by using a module that's "Alpha quality".
I am using perl 5.24. I am trying to learn Perl.
I had written a simple Perl code to connect to a DB. But gives error stating
DBI connect('database=vms','DBA',...) failed: (no error string) at simpleperl.pl line 13.
The code is
#!/usr/bin/perl
use DBI;
use DBD::SQLAnywhere;
my $driver = "SQLAnywhere";
my $database = "vms";
my $dsn = "DBI:$driver:database=$database";
my $userid = "DBA";
my $password = "admin";
my $dbh = DBI->connect($dsn, $userid, $password,{RaiseError => 1}) or die ("died connection:$DBI::errstr");
if($dbh)
{
print "Connection Established";
}
Can anyone point out what might be the problem here?
Note the following in DBD::SQLAnywhere documentation:
$dbh = DBI->connect( 'dbi:SQLAnywhere:ENG=demo', $userid, $passwd );
#!/usr/bin/perl
use strict;
use warnings;
use DBI;
my $driver = "SQLAnywhere";
my $database = "vms";
my $dsn = "DBI:$driver:ENG=$database";
my $userid = "DBA";
my $password = "admin";
my $dbh = DBI->connect($dsn, $userid, $password, {RaiseError => 1});
print "Connection established\n";
$dbh->disconnect;
Note also the following:
Always use strict and warnings.
You do not need use DBD::SQLAnywhere;. DBI will pick the driver based on what you specify in the connection string.
You specified {RaiseError => 1} in your connection options. That means, there is no need for the or die. DBI will croak if connect fails.
You probably want AutoCommit => 0 to go with that RaiseError => 1.
There is no need for the if ($dbh) following the connection attempt. You won't get there unless connect succeeded.
Given that fixing the connection string did not solve the problem and I do not have an instance of a SQLAnywhere database to test things, I am going to recommend you add:
DBI->trace( 5 );
before the connect call, and update your question with the trace information. See also TRACING.
My problem is that: the outputs are different, when I run the program on the linux machine, and on a web browser of another machine.
When I run the program on the linux machine, the output is:
Content-type: text/plain
11
22
username password
But when I put the program on an Apache Server, and access it using a browser on another machine, the output is simply:
11
It is probably because the program fails to connect to the database file. As I have set all the files to mode 777, that I do not have the permission is unlikely a reason.
Anyone know what the problem is and how to fix it?
#!/usr/bin/perl -w
use DBI;
print ("Content-type: text/plain\n\n");
print "11\n";
my $dbh = DBI->connect("dbi:SQLite:dbname=4140.db","","",{RaiseError => 1},) or die $DBI::errstr;
print "22\n";
my $sth = $dbh -> prepare("SELECT * FROM Credential");
$sth -> execute();
($usrname, $password) = $sth -> fetchrow();
$sth -> finish();
$dbh->disconnect();
print "$usrname $password\n";
The die strings are sent to STDERR and so won't appear in the HTTP message that is sent. You can solve this several ways, one of the simplest being to write an error handler for DBI errors that prints the error message to STDOUT.
You should also always use strict and use warnings. That way Perl will highlight many simple errors that you could otherwise easily overlook. use warnings is far superior to -w on the command line.
Take a look at this code as an example. Note that if you enable RaiseError as well as providing an error handler then DBI will raise an exception only if your error handler returns a false value.
#!/usr/bin/perl
use strict;
use warnings;
use DBI;
print ("Content-type: text/plain\n\n");
print "11\n";
my $dbh = DBI->connect('dbi:SQLite:dbname=4140.db','','',
{RaiseError => 1, PrintError => 0, HandleError => \&handle_error});
print "22\n";
my $sth = $dbh->prepare('SELECT * FROM Credential');
$sth->execute;
my ($usrname, $password) = $sth -> fetchrow();
print "$usrname $password\n";
sub handle_error {
my ($msg, $dbh, $rv) = #_;
print "DB Error: $msg\n";
0;
}
Yo should specify the complete path to your database file in order to avoid this kind of problems. Try this (if your database is at the same path as your script):
use FindBin '$Bin';
my $dbfile = "$Bin/4140.db";
my $dbh = DBI->connect("dbi:SQLite:dbname=$dbfile","","",{RaiseError => 1},) or die $DBI::errstr;
#...
Check your error log. You'll surely find that SQLite is failing to create 4140.db because of a permission error. You've made incorrect assumptions about the current directory.
I'm having an issue with storing sessions in a MySQL database using CGI::Session.
Here is a snippet
#!/usr/bin/perl
use CGI;
use CGI::Session;
use CGI::Session::Driver::mysql;
use DBI;
use DBD::mysql;
use Net::LDAPS;
require '../include/include.pl';
$LDAP_SERVER = 'my.test.ldap.example.com';
$LDAP_SSL_PORT = '636';
$LDAP_BASE = 'ou=users,dc=example,dc=com';
$ldap = Net::LDAPS->new($LDAP_SERVER, port=> $LDAP_SSL_PORT)
or die "Unable to create LDAP object because: $! \n";
$dbh = DBI->connect("DBI:mysql:host=$db_host;database=$db_name",$db_user,$db_pswd)
or die "Unable to connect to database: \"$DBI::errstr\" $! \n";
$q = CGI->new;
$usr = $q->param('usr') || undef;
$userDN = "uid=$usr,$LDAP_BASE";
if($usr) {
$pwd = $q->param('pwd');
$ldapMsg = $ldap->bind($userDN, password=>$pwd);
$result = $ldap->code;
if ($result == 0) {
$session = CGI::Session->new('driver:mysql', undef,
{ TableName=>'car_sessions',
IdColName=>'id',
DataColName=>'a_session',
Handle=>$dbh})
or die "Unable to create session because: $!";
$session->expire('+1h');
$session->param(-name=>'car_login', -value=>$usr);
$sess_cookie = $q->cookie(-name=>'CGISESSID', -value=>$session->id, -expires=>'+1h', -path=>'/hr_car/');
$login_cookie = $q->cookie(-name=>'car_login', -value=>$usr, -expires=>'+1h', -path=>'/hr_car/');
print $q->header(-cookie=>[$sess_cookie, $login_cookie], -location=>'manage.cgi');
}
LDAP is binding correctly, and the cookies are being set correctly, but NOTHING is showing up in my sessions table!
What could I be doing wrong??
I believe the problem is with auto-flushing being unreliable. There's an explicit problem with DBI handles going out of scope before auto-flush happens, so call $session->flush once you're done setting the session up and after you delete it.
You may mitigate this problem by using file-scoped lexicals instead of globals for $dbh and friends, Perl might be able to clean them up in the right order and it's just a good idea.
PS Turn on strict and warnings and declare all those variables. Your problem could have just as easily been caused by a typo and you'd never have known it.
I have a database query that I am running inside an eval, to trap the error. Problem is that the error message is outputting to console, even though it is being trapped. How do I stop the error message from doing this, as I want to parse it myself and spit back my own messages?
my $dbh = DBI->connect('dbi:Pg:dbname=database;host=localhost',
'user', 'pass',
{RaiseError => 1}
);
eval{
$sth = $dbh->prepare($sql);
$sth->execute;
};
if($#){
#Do my parse/print stuff here I know
}
It's not a good idea to trap and ignore errors, whether they are fatal or not. Also, it is not advisable to check $# in the way you are doing it (see the questions on this site about perl exceptions for better ways to trap exceptions; I use Try::Tiny below, which is arguably the lightest-weight route of all).
Instead of proceeding with a DBI operation when an earlier one might have failed, you should check error conditions at every step:
use strict; use warnings;
use Try::Tiny;
try {
my $sth = $dbh->prepare($sql) or die $dbh->errstr;
$sth->execute or die $sth->errstr;
} catch {
print "got error $_\n";
# return from function, or do something else to handle error
};
And remember, always use strict; use warnings; in every module and script. Your code excerpt suggests that you are not yet doing this.
You can specify 'PrintError => 0' in your connect call (or use HandleError):
my $dbh = DBI->connect('dbi:Pg:dbname=database;host=localhost', $user, $passwd, {
PrintError => 0,
RaiseError => 1,
});
Or to set per statement handle:
my $sth = $dbh->prepare("SELECT * from my_table");
$sth->{PrintError} = 0;
$sth->execute();
...etc.
Also, don't depend on $# for indicating an error. A better way to use eval is:
my $result = eval {
...
$sth->...etc.
1;
}
unless ($result) {
# Do error handling..log/print $#
}
eval { } will trap a fatal error (from a die or Carp::croak call), but not a non-fatal error message (from warn or carp). To handle warning messages, see how to install a warning handler in documentation for %SIG or warn.
A trivial workaround is to use a trivial warning handler inside your eval block.
eval {
local $SIG{__WARN__} = sub { };
...
};
See also: perlfaq7: How do I temporarily block warnings?