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System V Semaphore Arrays in Debian 6.x/Knoppix 6.x

A semaphore array is a System V IPC object that allows processes to synchronize access to shared resources. Any process can create a semaphore array, modify it and leave it for other processes to modify later on. Any process can immediately remove a semaphore array regardless of whether another process is using it. Semaphore arrays exist until they are removed or system shutdown.

The data strucuture of the semaphore array object is:
struct semid_ds
{
  struct ipc_perm sem_perm;
  time_t sem_otime;          /* last operation time  */
  time_t sem_ctime;          /* last change time */
  unsigned long sem_nsems;   /* count of sems in set */
};

Both commands list all the semaphore array objects in use on the system:
cat /proc/sysvipc/sem;
ipcs -s; ipcs -s -t; ipcs -s -p; ipcs -s -c; ipcs -s -l; ipcs -s -u;

Create semaphore array objects on the system:
ipcmk -S <number of elements> -p <permission bits>;

Remove semaphore array objects from the system:
ipcrm -S <semaphore key>;
ipcrm -s <semaphore id>;

Do you have a suggestion about how to improve this blog? Let's talk about it. Contact me at David.Brenner.Jr@Gmail.com or 720-584-5229.

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