# aptitude install libpq-dev

# yum install postgresql-devel

#include <stdio.h>
#include <stdlib.h>
#include <postgresql/libpq-fe.h>
#include <string.h>

int main(int argc, char *argv[]) {

     PGconn          *conn;
     PGresult        *res;
     int             rec_count;
     int             row;
     int             col;

     conn = PQconnectdb("dbname=ljdata host=localhost user=dataman password=supersecret");

     if (PQstatus(conn) == CONNECTION_BAD) {
          puts("We were unable to connect to the database");
          exit(0);
     }

     res = PQexec(conn, "update people set phonenumber=\'5055559999\' where id=3");

     res = PQexec(conn, "select lastname,firstname,phonenumber from people order by id");

     if (PQresultStatus(res) != PGRES_TUPLES_OK) {
          puts("We did not get any data!");
          exit(0);
     }

     rec_count = PQntuples(res);

     printf("We received %d records.\n", rec_count);
     puts("==========================");

     for (row=0; row<rec_count; row++) {
          for (col=0; col<3; col++) {
               printf("%s\t", PQgetvalue(res, row, col));
          }
          puts("");
     }

     puts("==========================");

     PQclear(res);
     PQfinish(conn);

     return 0;
}

$ cc -Wall -g tdb.c -o tdb -lpq

$ pg_config --includedir

SELECT extract(epoch FROM now());

select 1079497559::abstime::timestamp;