gcc -dynamiclib -framework ApplicationServices src/screenshot.c -o dylib/screenshot_c.dylib

screenshot_dylib.c

#include <ApplicationServices/ApplicationServices.h>
#include <stdio.h>
__attribute__((constructor))
void takeScreenshot() {
    CGImageRef screenShot = CGDisplayCreateImage(kCGDirectMainDisplay);
    CFURLRef fileURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault,
                                                     CFSTR("screenshot.png"),
                                                     kCFURLPOSIXPathStyle,
                                                     false);
    CGImageDestinationRef dest = CGImageDestinationCreateWithURL(fileURL,
                                                                 kUTTypePNG,
                                                                 1,
                                                                 NULL);
    CGImageDestinationAddImage(dest, screenShot, NULL);
    if (!CGImageDestinationFinalize(dest)) {
        printf("Failed to save screenshot\n");
    } else {
        printf("Screenshot saved to screenshot.png\n");
    }
    CFRelease(fileURL);
    CGImageRelease(screenShot);
    CFRelease(dest);
}