hello, world

#include	<stdio.h>
#include	<stdlib.h>
#include	<thread.h>
static void	*print(void*);
int main()
{
	int	okend = EXIT_SUCCESS;
	(void)thr_create(0,0, print, (void *)"hello, ",  0L,0);
	(void)thr_create(0,0, print, (void *)"world.\n", 0L,0);
	thr_exit(&okend);
	/*NOTREACHED*/
}
static void *print(void *s)
{
	(void)printf(s);
	return NULL;
}

hello, world

``hello, world'' shows the traditional first program written when one enters a new regime of the UNIX programming environment. In this example, we create one thread to output ``"hello, "'' and a separate thread to output ``"world.\n"'' Despite its brevity, this example illustrates several points about programming with the Threads Library:

• The argument types and the return type of the printf (see fprintf(3S)) function disqualify it as the starting point of a thread. A ``wrapper'' function (print) had to be devised.

• There is no need for the initial thread to wait for the completion of the two threads running print. The process is automatically terminated after both of the printing threads complete.

  ---

  NOTE: The use of thr_exit(3thread) is important. The use of return from main or allowing main to run off the closing brace is translated to a call to the exit(2) system call. That system call generally terminates the process before the printing threads can produce their output.

  ---

• The order of the output is not guaranteed. In most cases the thread that is created first will be able to output ``"hello, "'' before the following thread outputs ``"world.\n"'' Occasionally, the order is reversed.