#import <mach/mach.h>
#import <mach/mach_host.h>


-(void) print_free_memory {
    mach_port_t host_port;
    mach_msg_type_number_t host_size;
    vm_size_t pagesize;

    host_port = mach_host_self();
    host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
    host_page_size(host_port, &pagesize);        

    vm_statistics_data_t vm_stat;

    if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS)
        NSLog(@"Failed to fetch vm statistics");

    /* Stats in bytes */
    natural_t mem_used = (vm_stat.active_count +
                          vm_stat.inactive_count +
                          vm_stat.wire_count) * pagesize;
    natural_t mem_free = vm_stat.free_count * pagesize;
    natural_t mem_total = mem_used + mem_free;
    int iUsed = round(mem_used/100000);
    int iFree = round(mem_free/100000);
    int iTotal = round(mem_total/100000);
    NSLog(@"used: %d free: %d total: %d", iUsed, iFree, iTotal);
}

print_free_memory

Objective C