src/test/examples/testlibpq.c

   1 /*
   2  * $PostgreSQL:$
   3  *
   4  *
   5  * testlibpq.c
   6  *
   7  *              Test the C version of libpq, the PostgreSQL frontend library.
   8  */
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include "libpq-fe.h"
  12
  13 static void
  14 exit_nicely(PGconn *conn)
  15 {
  16         PQfinish(conn);
  17         exit(1);
  18 }
  19
  20 int
  21 main(int argc, char **argv)
  22 {
  23         const char *conninfo;
  24         PGconn     *conn;
  25         PGresult   *res;
  26         int                     nFields;
  27         int                     i,
  28                                 j;
  29
  30         /*
  31          * If the user supplies a parameter on the command line, use it as the
  32          * conninfo string; otherwise default to setting dbname=postgres and using
  33          * environment variables or defaults for all other connection parameters.
  34          */
  35         if (argc > 1)
  36                 conninfo = argv[1];
  37         else
  38                 conninfo = "dbname = postgres";
  39
  40         /* Make a connection to the database */
  41         conn = PQconnectdb(conninfo);
  42
  43         /* Check to see that the backend connection was successfully made */
  44         if (PQstatus(conn) != CONNECTION_OK)
  45         {
  46                 fprintf(stderr, "Connection to database failed: %s",
  47                                 PQerrorMessage(conn));
  48                 exit_nicely(conn);
  49         }
  50
  51         /*
  52          * Our test case here involves using a cursor, for which we must be inside
  53          * a transaction block.  We could do the whole thing with a single
  54          * PQexec() of "select * from pg_database", but that's too trivial to make
  55          * a good example.
  56          */
  57
  58         /* Start a transaction block */
  59         res = PQexec(conn, "BEGIN");
  60         if (PQresultStatus(res) != PGRES_COMMAND_OK)
  61         {
  62                 fprintf(stderr, "BEGIN command failed: %s", PQerrorMessage(conn));
  63                 PQclear(res);
  64                 exit_nicely(conn);
  65         }
  66
  67         /*
  68          * Should PQclear PGresult whenever it is no longer needed to avoid memory
  69          * leaks
  70          */
  71         PQclear(res);
  72
  73         /*
  74          * Fetch rows from pg_database, the system catalog of databases
  75          */
  76         res = PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_database");
  77         if (PQresultStatus(res) != PGRES_COMMAND_OK)
  78         {
  79                 fprintf(stderr, "DECLARE CURSOR failed: %s", PQerrorMessage(conn));
  80                 PQclear(res);
  81                 exit_nicely(conn);
  82         }
  83         PQclear(res);
  84
  85         res = PQexec(conn, "FETCH ALL in myportal");
  86         if (PQresultStatus(res) != PGRES_TUPLES_OK)
  87         {
  88                 fprintf(stderr, "FETCH ALL failed: %s", PQerrorMessage(conn));
  89                 PQclear(res);
  90                 exit_nicely(conn);
  91         }
  92
  93         /* first, print out the attribute names */
  94         nFields = PQnfields(res);
  95         for (i = 0; i < nFields; i++)
  96                 printf("%-15s", PQfname(res, i));
  97         printf("\n\n");
  98
  99         /* next, print out the rows */
 100         for (i = 0; i < PQntuples(res); i++)
 101         {
 102                 for (j = 0; j < nFields; j++)
 103                         printf("%-15s", PQgetvalue(res, i, j));
 104                 printf("\n");
 105         }
 106
 107         PQclear(res);
 108
 109         /* close the portal ... we don't bother to check for errors ... */
 110         res = PQexec(conn, "CLOSE myportal");
 111         PQclear(res);
 112
 113         /* end the transaction */
 114         res = PQexec(conn, "END");
 115         PQclear(res);
 116
 117         /* close the connection to the database and cleanup */
 118         PQfinish(conn);
 119
 120         return 0;
 121 }