Simplest possible fork example for Linux

fork.c

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#define __USE_GNU
#include <unistd.h>
#include <sys/wait.h>

int main(int argc, char **argv)
{
	pid_t child;
	int status;
	if(argc < 2)
	{
		printf("%s: command_to_execute [args]\n", argv[0]);
		exit(1);
	}
	switch(child = fork())
	{
		case -1:
			status = -1;
		case 0:
			execvp(argv[1], argv + 1);
			exit(127);
		default:
			if(TEMP_FAILURE_RETRY(waitpid(child, &status, 0)) != child)
				status = -1;
	}
	printf("=============\nChild's exit code: %d\n", (status));
	return 0;
}