Communicating with PostgreSQL Using LibPQ - PostgreSQL Developer's Guide - page 171

Here is the complete example of establishing a connection using all the methods
previously discussed:
/*----------------------------------------------------------------
*
*connection.c
*Connecting PostgreSQL Server using libpq
*
*IDENTIFICATION
*connection.c
*
*----------------------------------------------------------------
*/
#include<stdio.h>
#include<sys/types.h>
#include<stdlib.h>
#include<limits.h>
#include "libpq-fe.h"
#include "libpq/libpq-fs.h"
charconninfo[] = "hostaddr = '127.0.0.1' port = '5432' dbname =
'testdb'";
char *keyword[] = {"hostaddr", "port", "dbname"};
char *value[] = {"127.0.0.1", "5432", "testdb"};
int main(int argc, char **argv)
{
PGconn *conn; /* Connection Object */
/* Connect database using PQsetdb */
conn = PQsetdb(NULL, NULL, NULL, NULL, "testdb");
if (PQstatus(conn) == CONNECTION_BAD)
{
fprintf(stderr, "connection to database failed using
PQsetdb");
fprintf(stderr, "%s", PQerrorMessage(conn));
return -1;
}
fprintf(stdout, "Connection to database established using
PQsetdb\n");
PQfinish(conn);
/* Connect database using PQconnectdb */
conn = PQconnectdb(conninfo);
if (PQstatus(conn) == CONNECTION_BAD)
{
fprintf(stderr, "connection to database failed using
PQconnectdb\n");