errors when using semaphore

km603 · 02-10-2008, 12:16 AM

hi guys.

I don't get how to use semaphore in linux.

I am using ubuntu.

first of all, i have the following codes:

Code:

#include <semaphore.h>

sem_t sem;
int ret;
int count = 4;

/* to be shared among processes */
ret = sem_init(&sem, 1, count);

however when i complied the codes above, I got the following errors:

Code:

warning: data definition has no type or storage class
error: initializer element is not constant

what is wrong?

And another question, why can't I just use : semaphore mutex to declare?
like, semaphore mutex = 1;

thanks in advance.

tronayne · 02-11-2008, 08:03 AM

Take a look at the example program in the sem_wait manual page.