linux threading

#define _GNU_SOURCE

#include <stdio.h>  /* printf */
#include <unistd.h> /* open, read, fork */
#include <stdlib.h> /* malloc, exit */
#include <stdint.h> /* uint_32_t */
#include <string.h> /* strcmp, memcpy */
#include <pthread.h>
#include <sched.h>

void * pthread_func(void *arg)
{
    printf("%s\n", __FUNCTION__);

    while(1)
        sleep(10);

    return (void *)0;
}

int clone_func(void *arg)
{
    printf("%s\n", __FUNCTION__);

    while(1)
        sleep(10);

    return 0;
}

void fork_func(void)
{
    if(!fork()) {
        printf("%s\n", __FUNCTION__);
        while(1)
            sleep(10);
    }
}

void usage(char *argv0)
{
    printf("usage: %s [-tclf]\n", argv0);
    exit(0);
}

#define STACK_SIZE 4096

int main(int argc, char *argv[])
{
    char *stack = malloc(STACK_SIZE);
    pthread_t pt;

    if(argc != 2 || strlen(argv[1]) != 2 || argv[1][0] != '-')
        usage(argv[0]);
    switch(argv[1][1]) {
    case 't':
        pthread_create(&pt, NULL, pthread_func, 0);
        break;
    case 'c':
        clone(clone_func, stack + STACK_SIZE, 0, 0);
        break;
    case 'l':
        clone(clone_func, stack + STACK_SIZE,
              CLONE_FILES | CLONE_FS | CLONE_IO | CLONE_PARENT |
              CLONE_SIGHAND | CLONE_SYSVSEM | CLONE_THREAD | CLONE_VM, 0);
        break;
    case 'f':
        fork_func();
        break;
    default:
        usage(argv[0]);
    }

    while(1)
        sleep(10);

    return 0;
}