Question

Using C++, is there a way I could get basic information about the computer?

For example, is there a way I could check how much memory is being used (by the whole computer not just my computer), the total memory available, virtual memory usage, CPU usage, networks stats and so on?

I am using Mac OS X v10.6 (Snow Leopard), but I would prefer a solution that could be implemented for all Mac OSs (for example, Mac OS X v10.7 (Lion)).

Answer 1

For system-wide memory usage information under Mac OS X, open and read the file /usr/bin/vm_stat. Something like this:

static double ParseMemValue(const char * b)
{
    while((*b)&&(isdigit(*b) == false))
        b++;
    return isdigit(*b) ? atof(b) : -1.0;
}

// Returns a number between 0.0f and 1.0f, with 0.0f meaning all RAM is available, and 1.0f meaning all RAM is currently in use
float GetSystemMemoryUsagePercentage()
{
    FILE * fpIn = popen("/usr/bin/vm_stat", "r");
    if (fpIn)
    {
        double pagesUsed = 0.0, totalPages = 0.0;
        char buf[512];
        while(fgets(buf, sizeof(buf), fpIn) != NULL)
        {
            if (strncmp(buf, "Pages", 5) == 0)
            {
                double val = ParseMemValue(buf);
                if (val >= 0.0)
                {
                    if ((strncmp(buf, "Pages wired",  11) == 0) ||
                        (strncmp(buf, "Pages active", 12) == 0)
                       )

                        pagesUsed += val;

                    totalPages += val;
                }
            }
            else
              if (strncmp(buf, "Mach Virtual Memory Statistics", 30) != 0)
                  break; // Stop at "Translation Faults". We don't care
                         // about anything at or below that
        }
        pclose(fpIn);

        if (totalPages > 0.0)
            return (float) (pagesUsed/totalPages);
    }
    return -1.0f;  // Indicate failure
}

For a CPU usage indicator, do something like this:

#include <mach/mach_init.h>
#include <mach/mach_error.h>
#include <mach/mach_host.h>
#include <mach/vm_map.h>

static unsigned long long _previousTotalTicks = 0;
static unsigned long long _previousIdleTicks = 0;

// Returns 1.0f for "CPU fully pinned", 0.0f for "CPU idle", or somewhere in between
// You'll need to call this at regular intervals, since it measures the load between
// the previous call and the current one.
float GetCPULoad()
{
    host_cpu_load_info_data_t cpuinfo;
    mach_msg_type_number_t count = HOST_CPU_LOAD_INFO_COUNT;
    if (host_statistics(mach_host_self(), HOST_CPU_LOAD_INFO, (host_info_t)&cpuinfo, &count) == KERN_SUCCESS)
    {
        unsigned long long totalTicks = 0;
        for(int i=0; i<CPU_STATE_MAX; i++)
            totalTicks += cpuinfo.cpu_ticks[i];
        return CalculateCPULoad(cpuinfo.cpu_ticks[CPU_STATE_IDLE], totalTicks);
    }
    else
       return -1.0f;
}

float CalculateCPULoad(unsigned long long idleTicks, unsigned long long totalTicks)
{
    unsigned long long totalTicksSinceLastTime = totalTicks-_previousTotalTicks;
    unsigned long long idleTicksSinceLastTime  = idleTicks-_previousIdleTicks;
    float ret = 1.0f-((totalTicksSinceLastTime > 0) ? ((float)idleTicksSinceLastTime)/totalTicksSinceLastTime : 0);
    _previousTotalTicks = totalTicks;
    _previousIdleTicks  = idleTicks;
    return ret;
}

For network statistics, I don’t know the solution (other than maybe to run netstat and parse the results somehow… it depends on what network statistics you are interested in I suppose).