executing ncsim commands from verilog using system task

The Verilog source code doesn't know anything about the TCL interface that is controlling it. But the TCL does know about the Verilog. So the place to do this is in the TCL.

You can create a TCL breakpoint using the "stop" command that will watch for a signal and execute a command as a result. Before the simulation starts, execute a command like:

stop -condition {#event_signal == 1} -execute { input ./my_tcl_commands.tcl }

I 'd also want to know  an answer to that ...

   i.e.  call a  ncsim commnad  from verilog code.

reason is that    it is not that easy to find how to  educate  vmanager to take a tcl file  in my env ,  but it is  easy to change a verilog file.

 ( all i want is simple  'set severity  to avoid tons of  you have Z /X     on some signal '   that is clutering my log )

vManager can easily pass extra options to the simulator, the question really is which one fits your work flow best. You could, for example, create a bash-style script containing one line: "export XRUNOPTS='-input your_tcl_file.tcl'", then add the VSIF attribute "sve_name:/path/to/your/shell_file;". That can even be done interactively when you launch the VSIF, if you can't modify the VSIF for some reason.

There are other options like adding to run_script, sim_args or other VSIF attributes.

Trying to make a horrible Verilog-based hack to call Tcl via a backdoor that was never intended for such use is not trivial, and would be best avoided if possible....