How do I get the parameters passed in to an assembler program running in the UNIX System Services environment on z/OS?

Question

Trying something a bit different... I usually have a 'driver' program in C to call assembler but I would like to pass parameters from the command line to an assembler program in UNIX System Services. If I assemble a program and then run it as: mypgm p1 p2. Where would I expect to find the parameters p1 and p2? I was hoping off of R1, but that doesn't seem to be the case (although my assembler could easily just be bad). Note that I want an answer for UNIX System Services, not TSO or batch.

Answer 1

Assuming your program will be invoked from the shell, it should have parameters passed to it consistent with

• https://www.ibm.com/docs/en/zos/3.1.0?topic=csd-attach-exec-bpx1atx-bpx4atx-attach-zos-unix-program
• https://www.ibm.com/docs/en/zos/3.1.0?topic=descriptions-exec-bpx1exc-bpx4exc-run-program

The information that the service passes to the executable file that is to be run is a parameter list pointed to by register 1. The parameter list consists of the parameter addresses listed in this topic. In the last parameter address, the high-order bit is 1.

See attached diagram: passed parameter structure