iolib

/* file: main.c function: get and set capslock state complie: gcc -std=c99 -framework IOKit -framework CoreFoundation -o
 * capslock main.c usage: ./capslock [0|1|-1] 0 : capslock off 1 : capslock on -1 : toggle capslock state : print
 * current capslock state (0|1) * written and published as free software by Hiroto, 2015-06 */
#include <CoreFoundation/CoreFoundation.h>
#include <IOKit/IOKitLib.h>
#include <IOKit/hidsystem/IOHIDLib.h>
#include <IOKit/hidsystem/IOHIDParameter.h>
#include <libgen.h> // basename
#define CAPSLOCK_OFF 0
#define CAPSLOCK_ON 1
#define CAPSLOCK_TOGGLE -1
#define CAPSLOCK_QUERY 9
int main(int argc, char **argv) {
    kern_return_t kr;
    io_service_t ios;
    io_connect_t ioc;
    CFMutableDictionaryRef mdict;
    int op;
    bool state;
    if (argc < 2)
        op = CAPSLOCK_QUERY;
    else
        op = atoi(argv[1]);
    if (op != CAPSLOCK_ON && op != CAPSLOCK_OFF && op != CAPSLOCK_TOGGLE && op != CAPSLOCK_QUERY) {
        fprintf(stderr, "Usage: %s %s\n\t\%s\n\t%s\n\t%s\n\t%s\n", basename(argv[0]), "[0|1|-1]", " 0 : capslock off",
                " 1 : capslock on", "-1 : toggle capslock state", " : print current capslock state (0|1)");
        return 1;
    }
    mdict = IOServiceMatching(kIOHIDSystemClass);
    ios = IOServiceGetMatchingService(kIOMasterPortDefault, (CFDictionaryRef)mdict);
    if (!ios) {
        if (mdict)
            CFRelease(mdict);
        fprintf(stderr, "IOServiceGetMatchingService() failed: %x\n", kr);
        return (int)kr;
    }
    kr = IOServiceOpen(ios, mach_task_self(), kIOHIDParamConnectType, &ioc);
    IOObjectRelease(ios);
    if (kr != KERN_SUCCESS) {
        fprintf(stderr, "IOServiceOpen() failed: %x\n", kr);
        return (int)kr;
    }
    switch (op) {
        case CAPSLOCK_ON:
        case CAPSLOCK_OFF:
            state = (op == CAPSLOCK_ON);
            kr = IOHIDSetModifierLockState(ioc, kIOHIDCapsLockState, state);
            if (kr != KERN_SUCCESS) {
                IOServiceClose(ioc);
                fprintf(stderr, "IOHIDSetModifierLockState() failed: %x\n", kr);
                return (int)kr;
            }
            break;
        case CAPSLOCK_TOGGLE:
            kr = IOHIDGetModifierLockState(ioc, kIOHIDCapsLockState, &state);
            if (kr != KERN_SUCCESS) {
                IOServiceClose(ioc);
                fprintf(stderr, "IOHIDGetModifierLockState() failed: %x\n", kr);
                return (int)kr;
            }
            state = !state;
            kr = IOHIDSetModifierLockState(ioc, kIOHIDCapsLockState, state);
            if (kr != KERN_SUCCESS) {
                IOServiceClose(ioc);
                fprintf(stderr, "IOHIDSetModifierLockState() failed: %x\n", kr);
                return (int)kr;
            }
            break;
        case CAPSLOCK_QUERY:
            kr = IOHIDGetModifierLockState(ioc, kIOHIDCapsLockState, &state);
            if (kr != KERN_SUCCESS) {
                IOServiceClose(ioc);
                fprintf(stderr, "IOHIDGetModifierLockState() failed: %x\n", kr);
                return (int)kr;
            }
            break;
    }
    IOServiceClose(ioc);
    fprintf(stdout, "%d", (int)state);
    return 0;
}