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Old 01-20-2007, 12:26 AM   #1
ksrinivas
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Registered: Sep 2006
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how to get semphore count


Hello Everybody,

I am using "sem_getcount" to get the semaphore count. But the gcc compiler is not recognizing this. I am using Linux version 2.6.9-22.EL gcc version 3.4.4 20050721 (Red Hat 3.4.4-2)).

Can anyone please tell me how to get the semaphore count??

Thanks in advance,

Regards
Srinivas
 
Old 01-20-2007, 01:09 AM   #2
btmiller
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Registered: May 2004
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I'm not sure what exactly you are looking for but you can look at "sysctl kernel.sem". This page has some info on interpreting the parameters. See also the sysctl(2) man page for doing it via syscalls within a C program.
 
Old 01-20-2007, 02:01 AM   #3
ksrinivas
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Registered: Sep 2006
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Thanks for the reply.
Let me tell you What i am doing. In my C code, inside a blocking read call i waiting for the semaphore based on its count. So i will wait until some one releases the semaphore and the same i am checking through the sem_getcount().
So the problem that i am facing is "sem_getcount" not compilable. Is there any other way to get the semaphore count ???

Regards
Srinivas
 
Old 01-20-2007, 02:36 AM   #4
btmiller
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OK, so you don't actually need to know the number of semaphores available on your system, you just need to know the value of a particular one. I totally misread you, which is why it's good to be specific when asking a question so people have some idea what you want.

In any case, I have not written semaphore code in a looong time but I think you can do what you want using semctl with the GETVAL cmd argument. Please see "man semctl" for more details. Note that this is if you're using the System V style semaphore API. If you're using POSIX semaphores the correct function is sem_getvalue (the description is in the man page for sem_init).based on the fact you were looking for sem_getcount (note the underscore), I'm guessing you're using POSIX semaphores and so sem_getvalue is the function you seek.
 
  


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