get cpu usage in percent of current process on darwin

darwin-self-cpu-usage.c

#include <mach/bootstrap.h>
#include <mach/mach_host.h>
#include <mach/mach_port.h>
#include <mach/task.h>
#include <mach/mach_vm.h>
#include <mach/thread_act.h>
#include <sys/types.h>
#include <unistd.h>

#include <stdio.h>
#include <pthread.h>

float get_self_cpu_usage(void) {
    kern_return_t ret;
    thread_act_array_t threads;
    mach_msg_type_number_t tcnt;
    int cpuusg = 0;
    int i;

    ret = task_threads(mach_task_self(), &threads, &tcnt);
    if (ret != KERN_SUCCESS) {
        return -1.0;
    }

    for (i = 0; i < tcnt; ++i) {
        thread_basic_info_data_t info;
        mach_msg_type_number_t count = THREAD_BASIC_INFO_COUNT;

        ret = thread_info(threads[i], THREAD_BASIC_INFO, (thread_info_t)&info, &count);
        if (ret != KERN_SUCCESS) {
            continue;
        }
        if (!(info.flags & TH_FLAGS_IDLE)) {
            cpuusg += info.cpu_usage;
        }
        (void)mach_port_deallocate(mach_task_self(), threads[i]);
    }
    (void)mach_vm_deallocate(mach_task_self(), (mach_vm_address_t)(uintptr_t)threads, tcnt * sizeof(*threads));

    return (float)cpuusg / TH_USAGE_SCALE * 100.0;
}

void *thcb(void *arg) {
    int i;
    for (i = 0; i < 0x7FFFFFFF; ++i) {
        ;
    }
    return NULL;
}

int main() {
    pthread_t th;

    pthread_create(&th, NULL, thcb, NULL);

    sleep(1);
    printf("cpu usage: %.4f\n", get_self_cpu_usage());

    pthread_join(th, NULL);

    return 0;
}