How to share semaphore between processes

Take a look at this wiki article about IPC (InterProcess Communication) :

http://en.wikipedia.org/wiki/Inter-process_communication

There's a few ways to achieve this. Shared memory could be a good option for you :

http://en.wikipedia.org/wiki/Shared_memory

What system/OS are you developing for ?

I am using Linux fedora core 5.
I just researching for semaphore.h, there is a system call called sem_open to create named semaphore, I think it is possible that we can use that.

If all you want to share between the processes is that semaphore, then that's indeed an option.

More info for that on the man page for sem_open :

http://www.penguintutor.com/man/man.php?topic=sem_open§ion=3


    sem_t *sem = sem_open("/tmp/semname", O_CREAT, 0644, 0);
    if (sem == SEM_FAILED) {
      perror("sem_open() failed ");
    }

Chec kthe man pages for your system to get the implementation you'll use.

>sem_t *sem = sem_open("/tmp/semname", O_CREAT, 0644, 0);
This gives me segmentation fault
>sem_t *sem = sem_open("semname", O_CREAT, 0644, 0);
This Works ok.

What is the reason"?

Code
====
#include <semaphore.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
static sem_t *count_sem;
int main(int argc, char* argv[]){
char* semName=argv[1];
mode_t mode=0777;
unsigned int maxProcess=3;
unsigned int i=O_CREAT|O_EXCL;
int value=0;
count_sem=sem_open(semName,i,mode,maxProcess);
if (count_sem==(void *)-1){
printf("Error create named semaphore\n");
exit(1);
}
while(1){
      sem_getvalue(count_sem,&value);
      printf("value=%d\n",value);
      sem_wait(count_sem);
}


}

Several Test Results
================
[root@localhost Desktop]# ./sem "/tmp/name1"
Segmentation fault
[root@localhost Desktop]# ./sem "/tmp/name2"
Segmentation fault
[root@localhost Desktop]# ./sem "/tmp/name3"
Segmentation fault
[root@localhost Desktop]# ./sem "sem1"
Segmentation fault
[root@localhost Desktop]# ./sem "sem2"
value=3
value=2
value=1
value=0

[root@localhost Desktop]# ./sem "sem2"
Segmentation fault
[root@localhost Desktop]# ./sem "sem3"
value=3
value=2
value=1
value=0

Now I have faced a big problem...How to clean up the named semaphore that I have created and forget to clear? What is the proper way to actually clean up with code?

*What is the proper way to actually clean up the semaphore in the  code?

Thanks=)