dbm1.c

source code of begin linux programming

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <ndbm.h>
#include <string.h>

#define TEST_DB_FILE "/tmp/dbm1_test"
#define ITEMS_USED 3

/* A struct to use to test dbm */
struct test_data {
    char misc_chars[15];
    int  any_integer;
    char more_chars[21];
};

int main() {

    struct test_data items_to_store[ITEMS_USED];
    struct test_data item_retrieved;

    char key_to_use[20];
    int i, result;

    datum key_datum;
    datum data_datum;
    
    DBM *dbm_ptr;

    dbm_ptr = dbm_open(TEST_DB_FILE, O_RDWR | O_CREAT, 0666);
    if (!dbm_ptr) {
        fprintf(stderr, "Failed to open database\n");
        exit(EXIT_FAILURE);
    }

        /* put some data in the structures */
    memset(items_to_store, '\0', sizeof(items_to_store));
    strcpy(items_to_store[0].misc_chars, "First!");
    items_to_store[0].any_integer = 47;
    strcpy(items_to_store[0].more_chars, "foo");
    strcpy(items_to_store[1].misc_chars, "bar");
    items_to_store[1].any_integer = 13;
    strcpy(items_to_store[1].more_chars, "unlucky?");
    strcpy(items_to_store[2].misc_chars, "Third");
    items_to_store[2].any_integer = 3;
    strcpy(items_to_store[2].more_chars, "baz");

    for (i = 0; i < ITEMS_USED; i++) {
            /* build a key to use */
        sprintf(key_to_use, "%c%c%d",
            items_to_store[i].misc_chars[0],
            items_to_store[i].more_chars[0],
            items_to_store[i].any_integer);

            /* build the key datum strcture */
        key_datum.dptr = (void *)key_to_use;
        key_datum.dsize = strlen(key_to_use);
        data_datum.dptr = (void *)&items_to_store[i];
        data_datum.dsize = sizeof(struct test_data);

        result = dbm_store(dbm_ptr, key_datum, data_datum, DBM_REPLACE);
        if (result != 0) {
            fprintf(stderr, "dbm_store failed on key %s\n", key_to_use);
            exit(2);
        }
    } /* for */

        /* now try and retrieve some data */
    sprintf(key_to_use, "bu%d", 13); /* this is the key for the second item */
    key_datum.dptr = key_to_use;
    key_datum.dsize = strlen(key_to_use);

    data_datum = dbm_fetch(dbm_ptr, key_datum);
    if (data_datum.dptr) {
        printf("Data retrieved\n");
        memcpy(&item_retrieved, data_datum.dptr, data_datum.dsize);
        printf("Retrieved item - %s %d %s\n",
               item_retrieved.misc_chars,
               item_retrieved.any_integer,
               item_retrieved.more_chars);
    }
    else {
        printf("No data found for key %s\n", key_to_use);
    }

    dbm_close(dbm_ptr);

    exit(EXIT_SUCCESS);
}