(ipc.info.gz) semget

 
 1.6.1 semget
 ------------
 
 A semaphore array is allocated by a semget system call:
 
      semid = semget (key_t key, int nsems, int semflg);
 
    * `key' : an integer usually got from `ftok' or IPC_PRIVATE
 
    * `nsems' :
           # of semaphores in array (0 <= nsems <= SEMMSL <= SEMMNS)
 
           0 => dont care can be used when not creating the resource.
           If successful you always get access to the entire array
           anyway.
 
    * semflg :
           IPC_CREAT used to create a new resource
 
           IPC_EXCL used with IPC_CREAT to ensure failure if the
           resource exists.
 
           rwxrwxrwx  access permissions.
 
    * returns : semid on success. -1 on failure.
 
    An array of nsems semaphores is allocated if there is no resource
 corresponding to the given key. The access permissions specified are
 then copied into the `sem_perm' struct for the array along with the
 user-id etc. The user must use the IPC_CREAT flag or key = IPC_PRIVATE
 if a new resource is to be created.
 
 Errors:
 EINVAL : nsems not in above range (allocate).
 nsems greater than number in array (procure).
 EEXIST : (allocate) IPC_CREAT | IPC_EXCL specified and resource exists.
 EIDRM  : (procure) The resource was removed.
 ENOMEM : could not allocate space for semaphore array.
 ENOSPC : No arrays available (SEMMNI), too few semaphores available
 (SEMMNS).
 ENOENT : Resource does not exist and IPC_CREAT not specified.
 EACCES : (procure) do not have permission for specified access.
Info Catalog
(ipc.info.gz) Semaphores
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