Skip site navigation (1) Skip section navigation (2)

Re: trying to connect to PostgreSQL

From: "Phillip Smith" <phillip(dot)smith(at)weatherbeeta(dot)com(dot)au>
To: <kvnsmnsn(at)cs(dot)byu(dot)edu>,<pgsql-novice(at)postgresql(dot)org>
Subject: Re: trying to connect to PostgreSQL
Date: 2007-04-12 04:35:49
Message-ID: 00cf01c77cbc$0b74d350$9b0014ac@wbaus090 (view raw, whole thread or download thread mbox)
Lists: pgsql-novice
If I may ask, why are you trying to compile an individual file?

If you are just trying to install the client, you can just do this:
	gmake -C src/bin install
	gmake -C src/include install
	gmake -C src/interfaces install
	gmake -C doc install


-----Original Message-----
From: pgsql-novice-owner(at)postgresql(dot)org
[mailto:pgsql-novice-owner(at)postgresql(dot)org] On Behalf Of kvnsmnsn(at)cs(dot)byu(dot)edu
Sent: Wednesday, 11 April 2007 05:36
To: pgsql-novice(at)postgresql(dot)org
Subject: [NOVICE] trying to connect to PostgreSQL

I'm a relative newcomer to PostgreSQL.  I read the page on its website
that explained how to connect, and I tried to compile the following
example program.  I located a "libpq-fe.h" at "/usr/include/pgsql" so
I executed the command:

     cc -o pgsConnect -I/usr/include/pgsql pgsConnect.c

I got a whole bunch of error messages listing a whole bunches of oc-
currences of an "undefined reference to" some C function.  I went
through my local copy of "libpq-fe.h" and found references to each of
those functions, but they were all declared "extern".  Do I have to
actually have those functions defined somewhere in order to get this
code to compile?  If so, how can I get them defined?

The offending references were:

PQstatus          PQerrorMessage    PQexec            PQresultStatus
PQclear           PQnfields         PQfname           PQgetvalue
PQntuples         PQfinish

And the code I used was:

 * testlibpq.c
 *      Test the C version of libpq, the PostgreSQL frontend library.
#include <stdio.h>
#include <stdlib.h>
#include "libpq-fe.h"

static void
exit_nicely(PGconn *conn)

main(int argc, char **argv)
  const char *conninfo;
  PGconn     *conn;
  PGresult   *res;
  int         nFields;
  int         i,

   * If the user supplies a parameter on the command line, use it as the
   * conninfo string; otherwise default to setting dbname=postgres and using
   * environment variables or defaults for all other connection parameters.
  if (argc > 1)
    conninfo = argv[1];
    conninfo = "dbname = postgres";

  /* Make a connection to the database */
  conn = PQconnectdb(conninfo);

  /* Check to see that the backend connection was successfully made */
  if (PQstatus(conn) != CONNECTION_OK)
    fprintf(stderr, "Connection to database failed: %s",

   * Our test case here involves using a cursor, for which we must be inside
   * a transaction block.  We could do the whole thing with a single
   * PQexec() of "select * from pg_database", but that's too trivial to make
   * a good example.

  /* Start a transaction block */
  res = PQexec(conn, "BEGIN");
  if (PQresultStatus(res) != PGRES_COMMAND_OK)
    fprintf(stderr, "BEGIN command failed: %s", PQerrorMessage(conn));

   * Should PQclear PGresult whenever it is no longer needed to avoid memory
   * leaks

   * Fetch rows from pg_database, the system catalog of databases
  res = PQexec(conn, "DECLARE myportal CURSOR FOR select * from
  if (PQresultStatus(res) != PGRES_COMMAND_OK)
    fprintf(stderr, "DECLARE CURSOR failed: %s", PQerrorMessage(conn));

  res = PQexec(conn, "FETCH ALL in myportal");
  if (PQresultStatus(res) != PGRES_TUPLES_OK)
    fprintf(stderr, "FETCH ALL failed: %s", PQerrorMessage(conn));

  /* first, print out the attribute names */
  nFields = PQnfields(res);
  for (i = 0; i < nFields; i++)
  { printf("%-15s", PQfname(res, i));

  /* next, print out the rows */
  for (i = 0; i < PQntuples(res); i++)
    for (j = 0; j < nFields; j++)
    { printf("%-15s", PQgetvalue(res, i, j));


  /* close the portal ... we don't bother to check for errors ... */
  res = PQexec(conn, "CLOSE myportal");

  /* end the transaction */
  res = PQexec(conn, "END");

  /* close the connection to the database and cleanup */

  return 0;

                                ---Kevin Simonson

"You'll never get to heaven, or even to LA,
if you don't believe there's a way."
from _Why Not_

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not

*******************Confidentiality and Privilege Notice*******************

The material contained in this message is privileged and confidential to
the addressee.  If you are not the addressee indicated in this message or
responsible for delivery of the message to such person, you may not copy
or deliver this message to anyone, and you should destroy it and kindly
notify the sender by reply email.

Information in this message that does not relate to the official business
of Weatherbeeta must be treated as neither given nor endorsed by Weatherbeeta.
Weatherbeeta, its employees, contractors or associates shall not be liable
for direct, indirect or consequential loss arising from transmission of this
message or any attachments

In response to

pgsql-novice by date

Next:From: A. KretschmerDate: 2007-04-12 05:07:34
Subject: Re: server variables ?
Previous:From: AndreasDate: 2007-04-12 03:33:30
Subject: server variables ?

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group