Re: libpq Newbie question - Mailing list pgsql-general

Oops, fat fingered that one :-(

Make that -L/usr/local/pgsql/lib -lpq

Tim

----- Original Message -----
From: "Ronggolawe" <ngelawak@www2.us.postgresql.org>
To: <pgsql-general@postgresql.org.pgsql-interfaces@postgresql.org>
Sent: Thursday, November 29, 2001 10:34 PM
Subject: [GENERAL] libpq Newbie question


> Hi, I'm a newbie in postgresql, would like to know how to access database
> using libpq. I found example code on postgresql's site, however i'm not
able
> to execute the code it always giving me an error.
> I hope anyone could explain to me how to fix this.
> Thank you.
>
> Error:
> Undefined                       first referenced
>  symbol                             in file
> PQresultStatus                      /var/tmp/ccED8fcw.o
> PQclear                             /var/tmp/ccED8fcw.o
> PQexec                              /var/tmp/ccED8fcw.o
> PQerrorMessage                      /var/tmp/ccED8fcw.o
> PQstatus                            /var/tmp/ccED8fcw.o
> PQconsumeInput                      /var/tmp/ccED8fcw.o
> PQnotifies                          /var/tmp/ccED8fcw.o
> PQfinish                            /var/tmp/ccED8fcw.o
> PQsetdbLogin                        /var/tmp/ccED8fcw.o
> ld: fatal: Symbol referencing errors. No output written to a.out
> collect2: ld returned 1 exit status
>
> The code:
> /*
>  * testlibpq2.c
>  *  Test of the asynchronous notification interface
>  *
>  * Start this program, then from psql in another window do
>  *   NOTIFY TBL2;
>  *
>  * Or, if you want to get fancy, try this:
>  * Populate a database with the following:
>  *
>  *   CREATE TABLE TBL1 (i int4);
>  *
>  *   CREATE TABLE TBL2 (i int4);
>  *
>  *   CREATE RULE r1 AS ON INSERT TO TBL1 DO
>  *     (INSERT INTO TBL2 values (new.i); NOTIFY TBL2);
>  *
>  * and do
>  *
>  *   INSERT INTO TBL1 values (10);
>  *
>  */
> #include <stdio.h>
> #include "libpq-fe.h"
> void
> exit_nicely(PGconn *conn)
> {
>     PQfinish(conn);
>     exit(1);
> }
> main()
> {
>     char       *pghost,
>                *pgport,
>                *pgoptions,
>                *pgtty;
>     char       *dbName;
>     int         nFields;
>     int         i,
>                 j;
>     PGconn     *conn;
>     PGresult   *res;
>     PGnotify   *notify;
>     /*
>      * begin, by setting the parameters for a backend connection if the
>      * parameters are null, then the system will try to use reasonable
>      * defaults by looking up environment variables or, failing that,
>      * using hardwired constants
>      */
>     pghost = NULL;              /* host name of the backend server */
>     pgport = NULL;              /* port of the backend server */
>     pgoptions = NULL;           /* special options to start up the backend
>                                  * server */
>     pgtty = NULL;               /* debugging tty for the backend server */
>     dbName = getenv("USER");    /* change this to the name of your test
>                                  * database */
>     /* make a connection to the database */
>     conn = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName);
>     /*
>      * check to see that the backend connection was successfully made
>      */
>     if (PQstatus(conn) == CONNECTION_BAD)
>     {
>         fprintf(stderr, "Connection to database '%s' failed.\n", dbName);
>         fprintf(stderr, "%s", PQerrorMessage(conn));
>         exit_nicely(conn);
>     }
>     res = PQexec(conn, "LISTEN TBL2");
>     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
>     {
>         fprintf(stderr, "LISTEN command failed\n");
>         PQclear(res);
>         exit_nicely(conn);
>     }
>     /*
>      * should PQclear PGresult whenever it is no longer needed to avoid
>      * memory leaks
>      */
>     PQclear(res);
>     while (1)
>     {
>         /*
>          * wait a little bit between checks; waiting with select()
>          * would be more efficient.
>          */
>         sleep(1);
>         /* collect any asynchronous backend messages */
>         PQconsumeInput(conn);
>         /* check for asynchronous notify messages */
>         while ((notify = PQnotifies(conn)) != NULL)
>         {
>             fprintf(stderr,
>                  "ASYNC NOTIFY of '%s' from backend pid '%d' received\n",
>                     notify->relname, notify->be_pid);
>             free(notify);
>         }
>     }
>     /* close the connection to the database and cleanup */
>     PQfinish(conn);
>     return 0;
> }
>
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