Semid not available in second process

[Vinay L]

Hi All,

I am using Semaphores for one of my application on Mac OS(10.6). I am able to successfully create the semaphores, but I am not able to get the semid in another process. The same works fine on Linux machine. I can see the list of semaphores using ipcs command.


The Code Snippet is as follows:

First_Process:


#include<stdio.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <errno.h>

#define NUMSEMS 1

int main() {

int semid;

semid = semget("SEMTEST", NUMSEMS, 0666 | IPC_CREAT | IPC_EXCL);

printf("Sem id %d\n", semid);

return 0;
}

After running the above code’s executable, semaphore is created. I can verify using ipcs command.


$ipcs –s

Semaphores:

s 212860928 0x00001f68 --ra-ra-ra- offshore staff


After this I run my second process.

Second_Process:



#include<stdio.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <errno.h>


#define NUMSEMS 1

int main() {

int semid;

int i;

semid = semget("SEMTEST", NUMSEMS, 0);

printf("----Semid=%d---\n", semid);

return 0;

}

The output of the second process is -1, i.e it is getting semid as -1 eventhough the semkey, NUMSEMS is same(as provided in first process).

Please let me know the changes to be done, so that we can get semid in Second Process also.



Thanks & Regards,
Vinay

 

[macleuser]

I think you might get better help here:
http://macosx.com/forums/software-programming-web-scripting/
the above linked forum is for programming, this current forum you have posted in is for more general USE help. So, better visibility for more qualified people perhaps in the link above.