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POwhy are some posix shared memory segments and posix semaphores not visible to ipcs
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copied!<p>I built a client server application using posix shared memory and posix unnamed semaphores with pshared=1. The semaphores are placed inside the shared memory. The program runs fine, but when I type ipcs -m or ipcs -s, I do not see any shared memory segments or semaphores that I created. Why is it so?</p> <pre><code>/* Server main function for implementing client server program using Posix Shared Memory and Posix Unnamed Semaphores*/ #include "shm_sem.h" int main(int argc,char ** argv) { int fd; struct shmstruct *ptr; shm_unlink(MYSHM); // delete shared memory segment, if it already exists /* create shared memory, set its size, map it and close descriptor */ fd=shm_open(MYSHM,O_RDWR|O_CREAT|O_EXCL,0777); ptr=mmap(NULL,sizeof(struct shmstruct),PROT_READ|PROT_WRITE,MAP_SHARED,fd,0); // truncate the size of shared memory to the size of shmstruct ftruncate(fd,sizeof(struct shmstruct)); close(fd); // initialize the semaphores in shared memory sem_init(&ptr->client_mutex,1,1); // set client semaphore to 1 sem_init(&ptr->server_mutex,1,0); // set server semaphore to 0 for(;;) { serverPosixShmSem(ptr); // calling server } } </code></pre> <hr> <pre><code>/* Server main function for implementing client server program using Posix Shared Memory and Posix Unnamed Semaphores*/ #include "shm_sem.h" int main(int argc,char ** argv) { int fd; struct shmstruct *ptr; shm_unlink(MYSHM); // delete shared memory segment, if it already exists /* create shared memory, set its size, map it and close descriptor */ fd=shm_open(MYSHM,O_RDWR|O_CREAT|O_EXCL,0777); ptr=mmap(NULL,sizeof(struct shmstruct),PROT_READ|PROT_WRITE,MAP_SHARED,fd,0); // truncate the size of shared memory to the size of shmstruct ftruncate(fd,sizeof(struct shmstruct)); close(fd); // initialize the semaphores in shared memory sem_init(&ptr->client_mutex,1,1); // set client semaphore to 1 sem_init(&ptr->server_mutex,1,0); // set server semaphore to 0 for(;;) { serverPosixShmSem(ptr); // calling server } } </code></pre>

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