In reply to rkg_:
The uvm_cmdline_processor is a class used to query the command line. It is slightly more flexible than SystemVerilog’s $value$plusargs. It calls DPI-C code to read the entire command line and has a number of methods to get sets of values.
The first time it gets used is when calling uvm_root:run_test.
I’m guessing you are asking about it because you encountered some problem or misunderstanding.