TSO/batch command - Hercules command interface

The sends a command to the Hercules console and retrieves the
response, which can be shown on the console, listed in TSO as
OUTTRAPable or as batch sysout.

The program operates in 3 modes, console, TSO or batch.

Console mode is selected when the job step program is not
IKJ-something and the parm field is not SYSIN. The command is in
the parm field, the response is written to the operator console
using WTO. Maximum command length is 160, opsys permitting.

TSO mode is selected when the job step program is IKJ-something
and the parm field is not SYSIN. The command is in the parm field,
maximum command length is 160.
The response is written to the TSO session using PUTLINEs, making
it OUTTRAPable in a REXX pgm.

Batch mode is selected when the parm field is SYSIN. Commands are
read from the HRCCMD libref, one line per command. File defs are
FB/80. Responses are written to the HRCLST libref with filedefs
FB/140. Commands are echoed to the output, input lines starting
with an asterix (*) are comments and are ignored, as are blank
lines.

In all cases the maximum total size of the response buffer is
4096, which still allows for rather a lot of lines.

Batch sample:
       //HRCB     EXEC PGM=HERCCMD,PARM='SYSIN'
       //HERCLST  DD SYSOUT=*
       //HERCCMD  DD *
       * Program version
       cmdver
       * List all dasd devices
       devlist dasd

Console sample:
       //HRCC     EXEC PGM=HERCCMD,PARM='devlist dasd'

TSO sample (well, REXX actually):
       zz=outtrap('lst.')
       Address TSO "HERCCMD devlist dasd"
       zz=outtrap('off')
       do n=1 to lst.0
         say '->' lst.n
       end

Return codes
  0  All ok
  1  List truncation occurred
 >1  Something bad happened, a message will explain what.


Notes
 -  In the console or TSO mode you can use the CMDVER command to
    return the program version. The version is automatically
    written in batch mode.
 -  The respose buffer is set to 4096 bytes, so long responses
    like a large DEVLIST might be truncated.