Build a C application

Prerequisites

The tutorial assumes that you have:

  • installed YugabyteDB, and created a universe. If not, please follow these steps in the Quick Start guide.
  • have a 32-bit (x86) or 64-bit (x64) architecture machine.
  • have gcc 4.1.2+, clang 3.4+ installed.

Install the C driver (libpq)

The C driver is already available as part of the YugabyteDB installation. You can use it by setting the LD_LIBRARY_PATH as follows :-

  1. $ export LD_LIBRARY_PATH=<yugabyte-install-dir>/postgres/lib

Alternatively, you can download the PostgreSQL binaries or build the driver from source as documented here.

Working example

Sample C code

Create a file ybsql_hello_world.c and copy the contents below:

  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include "libpq-fe.h"
  5. int
  6. main(int argc, char **argv)
  7. {
  8.   const char *conninfo;
  9.   PGconn     *conn;
  10.   PGresult   *res;
  11.   int         nFields;
  12.   int         i, j;
  14.   /* connection string */
  15.   conninfo = "host=127.0.0.1 port=5433 dbname=yugabyte user=yugabyte password=yugabyte";
  17.   /* Make a connection to the database */
  18.   conn = PQconnectdb(conninfo);
  20.   /* Check to see that the backend connection was successfully made */
  21.   if (PQstatus(conn) != CONNECTION_OK)
  22.   {
  23.       fprintf(stderr, "Connection to database failed: %s",
  24.           PQerrorMessage(conn));
  25.       PQfinish(conn);
  26.       exit(1);
  27.   }
  29.   /* Create table */
  30.   res = PQexec(conn, "CREATE TABLE employee (id int PRIMARY KEY, \
  31.                                              name varchar, age int, \
  32.                                              language varchar)");
  34.   if (PQresultStatus(res) != PGRES_COMMAND_OK)
  35.   {
  36.       fprintf(stderr, "CREATE TABLE failed: %s", PQerrorMessage(conn));
  37.       PQclear(res);
  38.       PQfinish(conn);
  39.       exit(1);
  40.   }
  41.   PQclear(res);
  42.   printf("Created table employee\n");
  44.   /* Insert a row */
  45.   res = PQexec(conn, "INSERT INTO employee (id, name, age, language) \
  46.                       VALUES (1, 'John', 35, 'C')");
  48.   if (PQresultStatus(res) != PGRES_COMMAND_OK)
  49.   {
  50.       fprintf(stderr, "INSERT failed: %s", PQerrorMessage(conn));
  51.       PQclear(res);
  52.       PQfinish(conn);
  53.       exit(1);
  54.   }
  55.   PQclear(res);
  56.   printf("Inserted data (1, 'John', 35, 'C')\n");
  59.   /* Query the row */
  60.   res = PQexec(conn, "SELECT name, age, language FROM employee WHERE id = 1");
  61.   if (PQresultStatus(res) != PGRES_TUPLES_OK)
  62.   {
  63.       fprintf(stderr, "SELECT failed: %s", PQerrorMessage(conn));
  64.       PQclear(res);
  65.       PQfinish(conn);
  66.       exit(1);
  67.   }
  69.   /* print out the rows */
  70.   nFields = PQnfields(res);
  71.   for (i = 0; i < PQntuples(res); i++)
  72.   {
  73.       printf("Query returned: ");
  74.       for (j = 0; j < nFields; j++)
  75.     printf("%s ", PQgetvalue(res, i, j));
  76.       printf("\n");
  77.   }
  78.   PQclear(res);
  80.   /* close the connection to the database and cleanup */
  81.   PQfinish(conn);
  83.   return 0;
  84. }

Run the application

You can compile the file using gcc or clang.For gcc, you can use:

  1. $ gcc ybsql_hello_world.c -lpq -I<yugabyte-install-dir>/postgres/include -o ybsql_hello_world

Run with:

  1. $ ./ybsql_hello_world

You should see the following output:

  1. Created table employee
  2. Inserted data (1, 'John', 35, 'C')
  3. Query returned: John 35 C