PostgresSQL server connectiong problem with C-language...

["Madhu Sudhana Rao" <madhu542(at)gmail(dot)com>]

Hi,

I wrote a C-program for connecting to postgresSQL server and get the
data from the database.

The program is as fallows:-
Code: ( c )

#include <stdio.h>
#include <stdlib.h>
#include "libpq-fe.h"                                   /* libpq header file */
int
main()
{
          char        state_code[3];
          char        query_string[256];                      /* holds
constructed SQL query */
          PGconn     *conn;                                   /* holds
database connection */
          PGresult   *res;
          int         i;
          conn = PQconnectdb("dbname=test");                  /*
connect to the database */
          if (PQstatus(conn) == CONNECTION_BAD)               /* did
the database connection fail? */
          {
              fprintf(stderr, "Connection to database failed.\n");
              fprintf(stderr, "%s", PQerrorMessage(conn));
              exit(1);
          }
          printf("Enter a state code: ");                     /*
prompt user for a state code */
          scanf("%2s", state_code);
          sprintf(query_string,                               /*
create an SQL query string */
                  "SELECT name \
                   FROM statename \
                   WHERE code = '%s'", state_code);
           res = PQexec(conn, query_string);                   /* send
the query */
           if (PQresultStatus(res) != PGRES_TUPLES_OK)         /* did
the query fail? */
           {
               fprintf(stderr, "SELECT query failed.\n");
               PQclear(res);
               PQfinish(conn);
               exit(1);
           }
           for (i = 0; i < PQntuples(res); i++)                /* loop
through all rows returned */
                printf("%s\n", PQgetvalue(res, i, 0));          /*
print the value returned */
           PQclear(res);                                       /* free result */
           PQfinish(conn);                                     /*
disconnect from the database */
           return 0;
        }

I changed the postgresql.conf and pg_hba.conf files.

listen_addresses = '*'                  # what IP address(es) to listen on;
                                        # comma-separated list of addresses;
                                        # defaults to 'localhost', '*' = all
                                        # (change requires restart)
port = 5432                             # (change requires restart)
max_connections = 100
----------------------------------------------------------------------------

# TYPE  DATABASE    USER        CIDR-ADDRESS          METHOD
local   all         all                               trust

# The same using local loopback TCP/IP connections.
#
# TYPE  DATABASE    USER        CIDR-ADDRESS          METHOD
host    all         all         0.0.0.0/0          trust




every time I a getting the same error when I was trying to run the program:-

Connection to database failed.
could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?



Thanks for reading this long mail.
could any one plz help me how to solve this problem...


Thanks & Regards...
Madhu.