BPX1MCT (shmctl) example

The following code retrieves the size of the shared memory segment. For the callable service, see shmctl (BPX1MCT, BPX4MCT) — Perform shared memory control operations. For the data structure, see BPXYSHM—Map interprocess communication shared memory segments. AMODE 64 callers use BPX4MCT (shmctl) example.

                                              
         LA    R15,BUFFERA                                              
         ST    R15,BUFA                                                 
         SPACE ,                                                        
         CALL  BPX1MCT,              Shared memory segment control     +
               (SHM_ID,              Input: Shared memory segment ID   +
               =A(IPC_STAT),         Input: Command            BPXYIPC +
               BUFA,                 Input: ->SHMID_DS or 0    BPXYSHM +
               RETVAL,               Return value: 0, -1 or value      +
               RETCODE,              Return code                       +
               RSNCODE),             Reason code                       +
               VL,MF=(E,PLIST)       ----------------------------------