Perl + C + DBI

[Mathias Hennersdorf <ma...@web.de>]

Hi!

I`ve a big problem:
I `ve written 2 scripts, one in perl (db_connect.pl) and one in c
(connect.c).
The C-Script shoul connect to a DB by the Perlskript.
But i doesn`t get any result.

Greetings

Mathias

Here the scripts, every idea is welcome:

connect.c

#include <EXTERN.h>
#include </usr/lib/perl5/5.8.0/i386-linux-thread-multi/CORE/perl.h>
#include </usr/include/stdio.h>

#ifdef __cplusplus
#  define EXTERN_C extern "C"
#else
#  define EXTERN_C extern
#endif

static PerlInterpreter *my_perl;

static void xs_init (pTHX);

EXTERN_C void boot_DynaLoader (pTHX_ CV* cv);

EXTERN_C void
xs_init(pTHX)
{
char *file = __FILE__;
newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file);
}

PerlOpenDB(char *db_name)
{
int a;
dSP;
ENTER;
SAVETMPS;
PUSHMARK(SP);
XPUSHs(sv_2mortal(newSVpv(db_name,a)));

PUTBACK;
call_pv("db_connect", G_SCALAR);
SPAGAIN;
printf("db open: %d wurde %d geöffnet!\n",db_name,POPi);
PUTBACK;
FREETMPS;
LEAVE;
}

int main (int argc, char **argv, char **env)
{
char *loader[] = { "", "db_connect.pl" };

my_perl = perl_alloc();
perl_construct( my_perl );

perl_parse(my_perl, xs_init, argc, loader, NULL);
//perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL);
perl_run(my_perl);

PerlOpenDB("testdb");

perl_destruct(my_perl);
perl_free(my_perl);
}


the perl-script:


#!/usr/bin/perl -w

use DBI;

sub db_open_pg
{
$data_source_pgsql="dbi:Pg:dbname=$db_name";

$dbuser="postgres";
$dbpass="";


$dbh_pgsql = DBI -> connect ($data_source_pgsql, $dbuser, $dbpass );

print "Errors: $DBI::err, $DBI::errstr\n" if ($DBI::err || $DBI::errstr);
if (! defined $dbh_pgsql)
{
print "No connection to:$db_name: $DBI::errstr\n";
$opendb=0;

}
else
{
print "Connect to $db_name !\n";
$opendb=1;
}

return $opendb;
}



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Re: Perl + C + DBI

[Richard Schilling <rs...@nationalinformatics.net>]

I am not familiar enough with the syntax for invoking PERL through a 
C/C++ program to comment on that.

But, in your PERL script you have the following:

	if (! defined $dbh_pgsql)
	{
	print "No connection to:$db_name: $DBI::errstr\n";
	$opendb=0;

	}
	else
	{
	print "Connect to $db_name !\n";
	$opendb=1;
	}

You might, just for fun, try to change the if statement:

	if ( !defined($dbh_pgsql))
	{

	. . .

Notice I put "!" right next to define and also used paranthesis to call 
the define function call.  Perhaps the other form you had works too but 
I always get a good result when I use the form I'm suggesting.

Good luck.


--Richard Schilling



On 2003.05.15 05:33 Mathias Hennersdorf wrote:
> Hi!
> 
> I`ve a big problem:
> I `ve written 2 scripts, one in perl (db_connect.pl) and one in c
> (connect.c).
> The C-Script shoul connect to a DB by the Perlskript.
> But i doesn`t get any result.
> 
> Greetings
> 
> Mathias
> 
> Here the scripts, every idea is welcome:
> 
> connect.c
> 
> #include <EXTERN.h>
> #include </usr/lib/perl5/5.8.0/i386-linux-thread-multi/CORE/perl.h>
> #include </usr/include/stdio.h>
> 
> #ifdef __cplusplus
> #  define EXTERN_C extern "C"
> #else
> #  define EXTERN_C extern
> #endif
> 
> static PerlInterpreter *my_perl;
> 
> static void xs_init (pTHX);
> 
> EXTERN_C void boot_DynaLoader (pTHX_ CV* cv);
> 
> EXTERN_C void
> xs_init(pTHX)
> {
> char *file = __FILE__;
> newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file);
> }
> 
> PerlOpenDB(char *db_name)
> {
> int a;
> dSP;
> ENTER;
> SAVETMPS;
> PUSHMARK(SP);
> XPUSHs(sv_2mortal(newSVpv(db_name,a)));
> 
> PUTBACK;
> call_pv("db_connect", G_SCALAR);
> SPAGAIN;
> printf("db open: %d wurde %d geöffnet!\n",db_name,POPi);
> PUTBACK;
> FREETMPS;
> LEAVE;
> }
> 
> int main (int argc, char **argv, char **env)
> {
> char *loader[] = { "", "db_connect.pl" };
> 
> my_perl = perl_alloc();
> perl_construct( my_perl );
> 
> perl_parse(my_perl, xs_init, argc, loader, NULL);
> //perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL);
> perl_run(my_perl);
> 
> PerlOpenDB("testdb");
> 
> perl_destruct(my_perl);
> perl_free(my_perl);
> }
> 
> 
> the perl-script:
> 
> 
> #!/usr/bin/perl -w
> 
> use DBI;
> 
> sub db_open_pg
> {
> $data_source_pgsql="dbi:Pg:dbname=$db_name";
> 
> $dbuser="postgres";
> $dbpass="";
> 
> 
> $dbh_pgsql = DBI -> connect ($data_source_pgsql, $dbuser, $dbpass );
> 
> print "Errors: $DBI::err, $DBI::errstr\n" if ($DBI::err ||
> $DBI::errstr);
> if (! defined $dbh_pgsql)
> {
> print "No connection to:$db_name: $DBI::errstr\n";
> $opendb=0;
> 
> }
> else
> {
> print "Connect to $db_name !\n";
> $opendb=1;
> }
> 
> return $opendb;
> }
> 
> 
> 
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