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#include <stdio.h>
#include <stdlib.h>
#include "pthread.h"
#include "semaphore.h"
 
sem_t mutex;
int s = 0;
 
void* job (void* id) {
	printf("Start thread ID #%d\n", (int) id);
	while(1) {
		//sleep(1); //(1)
		sem_wait(&mutex);
		//sleep(1); //(2)
			printf("Thread #%d is doing math. %d + 1 = %d.\n", (int) id, s, s+1);
			s++;
		//sleep(1);	//(3)
		sem_post(&mutex);
		sleep(1);	//(4)
	}
}
 
int main() {
	pthread_t thread[10];
 
	int i;
	sem_init(&mutex, 0, 1);
	for (i = 0; i<10; ++i)
		pthread_create(&(thread[i]), NULL, job, (void*) i);
 
	sleep(100);
}
 

prog.c: In function ‘job’:
prog.c:19: warning: implicit declaration of function ‘sleep’
prog.c: In function ‘main’:
prog.c:32: warning: control reaches end of non-void function
/home/outB8N/ccWyCt1j.o: In function `main':
prog.c:(.text+0x2e): undefined reference to `sem_init'
prog.c:(.text+0x56): undefined reference to `pthread_create'
/home/outB8N/ccWyCt1j.o: In function `job':
prog.c:(.text+0xa8): undefined reference to `sem_wait'
prog.c:(.text+0xe4): undefined reference to `sem_post'
collect2: ld returned 1 exit status

Standard output is empty