BPX1FCT (fcntl) example

The code for the second example sets a shared byte range lock. For the callable service, see fcntl (BPX1FCT, BPX4FCT) — Control open file descriptors. For the data structure, see BPXYFCTL — Command values and flags for fcntl, BPXYBRLK — Map byte range lock request for fcntl, and BPXYOPNF — Map flag values for open. AMODE 64 callers use BPX4FCT (fcntl) example.

                                              
* for 2nd parm F_DUPFD, F_DUPFD2           3rd parm file desc no..      
* for 2nd parm F_GETFD, F_GETFL            3rd parm 0                   
* for 2nd parm F_SETFD                     3rd parm BPXYFCTL            
* for 2nd parm F_GETLK, F_SETLK, F_SETLKW  3rd parm BPXYBRLK            
* for 2nd parm F_SETFL                     3rd parm BPXYOPNF            
         SPACE ,                                                        
* Example 1 - duplicate file descriptor                                 
         MVC   FILEDES2,=F'20'       Get free file descriptor >= 20     
         SPACE ,                                                        
         CALL  BPX1FCT,              General purpose file control      +
               (=A(STDERR_FILENO),   Input: File descriptor            +
               =A(F_DUPFD),          Input: Action, BPXYFCTL           +
               FILEDES2,             Input: Argument #/0/FCTL/BRLK/OPNF+
               RETVAL,               Return value: 0, -1 or action     +
               RETCODE,              Return code                       +
               RSNCODE),             Reason code                       +
               VL,MF=(E,PLIST)       ---------------------------------- 
         SPACE ,                                                        
* Example 2 - duplicate file descriptor                                 
         MVC   FILEDES2,=F'20'       Get next higher file descriptor    
         LA    R15,BRLK                                                 
         ST    R15,BRLKA                                                
         XC    BRLK(BRLK#LENGTH),BRLK      Null out BRLK                
         MVC   L_TYPE,=AL2(F_RDLCK)        Lock type = shared           
         MVC   L_WHENCE,=AL2(SEEK_CUR)     Whence = from current cursor 
         SPACE ,                                                        
         CALL  BPX1FCT,              General purpose file control      +
               (=A(STDERR_FILENO),   Input: File descriptor            +
               =A(F_SETLK),          Input: Action, BPXYFCTL           +
               BRLKA,                Input: Argument #/0/FCTL/BRLK/OPNF+
               RETVAL,               Return value: 0, -1 or action     +
               RETCODE,              Return code                       +
               RSNCODE),             Reason code                       +
               VL,MF=(E,PLIST)       ----------------------------------