Dear All,
I am looking for a Sample Semaphore program on linux, Plz help me
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Dear All,
I am looking for a Sample Semaphore program on linux, Plz help me
GIFY.Quote:
Originally Posted by ashok449
I have an Idea on Semaphores but dont know how to apply on a real time application.
is this semaphore signalling? thats a cool little programming idea for a laugh, morse code translator would be good too..
What sort of "real time" are we talking here?Quote:
Originally Posted by ashok449
Using Linux as a base for strict real-time applications is like using a Ford Transit to enter a Formula 3 race - it hasn't got a chance.
On the other hand, if you are just after some "decent human perceived realtime" then I suppose it would work.
What exactly is the problem with applying semaphores on a realtime application - it would be better if you discussed at a "bigger picture" level what you want to achieve, because that would allow us to give you sensible advice.
--
Mats
More likely ashok449 is referring to the programming technique rather than the communication method.Quote:
is this semaphore signalling? thats a cool little programming idea for a laugh, morse code translator would be good too..
Ok, here is some code I found on net. Plz tell me how this works.
thanks in advance ...Code:#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#define KEY (1492)
void main()
{
int id;
struct sembuf operations[1];
int retval;
id = semget(KEY, 1, 0666);
if(id < 0)
{
fprintf(stderr, "Program sema cannot find semaphore, exiting.\n");
exit(0);
}
/* Do a semaphore V-operation. */
printf("Program sema about to do a V-operation. \n");
operations[0].sem_num = 0;
/* Which operation? Add 1 to semaphore value : */
operations[0].sem_op = 1;
/* Set the flag so we will wait : */
operations[0].sem_flg = 0;
/* So do the operation! */
retval = semop(id, operations, 1);
if(retval == 0)
{
printf("Successful V-operation by program sema.\n");
}
else
{
printf("sema: V-operation did not succeed.\n");
perror("REASON");
}
}
I personally think that code is pretty clear [even tho' I've never seen that piece of code before] - can you perhaps clarify which part of the code you don't understand.
--
Mats
retval = semop(id, operations, 1);
if retval ==0 then semop is successfull which means I need to place my code here, If so how to aquire/release again.
if retval ==0 then semop is successfull which means I need to place my code here, If so how to aquire/release again.Code:
if(retval ===0)
{
// semop success
do some stuff .....
// how to release or aquire lock
operations[0].sem_num = 0;
/* Which operation? Add 1 to semaphore value : */
operations[0].sem_op = -1;
/* Set the flag so we will wait : */
operations[0].sem_flg = 0;
semop(id, operations, 1); // is this corrrect
}
That looks about right, yes.
--
Mats
Now, Anyone can give me a small real-time example on semaphore
Seriously?
Doesn't google work!? I'll have to quote brewbuck on this -- GIFY
zacs7 and brewbuck, you see in this thread I almost provide everything except a clarification which I require. Thats all I need and thats all about a forum is.
If getting sample code from google is enough then what is the requirement of a forum.
Forum means expressing yourself and getting advices.
Anyhow thanks for everything...
So you expressed youself and got a very good advice (go search the web). Now it is upto you if you will follow the advice and learn something or ignore it and stay as uneducated as you are now.Quote:
Originally Posted by ashok449