DisplayInfo

displayinfo.c

#include <CoreFoundation/CoreFoundation.h>
#include <ApplicationServices/ApplicationServices.h>

int main (int argc, const char * argv[]) {
    CGDisplayCount    displayCount;
    CGDirectDisplayID displays[4];
    int               i;

    CGGetOnlineDisplayList(4, displays, &displayCount);

    for (i = 0; i < displayCount; ++i) {
        CGRect rect = CGDisplayBounds(displays[i]);
        printf("%d: %.0fx%.0f ( ", i, rect.size.width, rect.size.height);

        if (CGDisplayIsActive(displays[i]))
            printf("active ");

        if (CGDisplayIsAsleep(displays[i]))
            printf("sleep ");

        if (CGDisplayIsBuiltin(displays[i]))
            printf("builtin ");

        if (CGDisplayIsMain(displays[i]))
            printf("main ");

        if (CGDisplayIsOnline(displays[i]))
            printf("online ");

        printf(")\n");
    }

    return 0;
}