I'm sharing this code.  This is an example of passing strings back and forth from SystemVerilog and DPI.  Some of these features aren't available until IUS6.0.

----file top.v--------
module top ();

import "DPI-C" context pass_string_c= task pass_string_sv(input string a);

import "DPI-C" context string_c2v_c= function string string_c2v_sv();

string some_string;

// This doesnt work in IUS583, will work in IUS6.0
export "DPI-C" print_string_c = function print_string_sv;
   
function void print_string_sv(input string aaa);  
 $display("Exported Verilog String=  %s", aaa);
endfunction

initial
  begin
  some_string = "pass it ON";
  // enable when running IUS6.0
  pass_string_sv(some_string);  // pass string to C
  $display("Verilog: %s \n", string_c2v_sv() );  // get string from C
 $finish; 
end

endmodule

-----file main_task.c-----
#include <stdio.h>
#include <svdpi.h>

// to use io_printf (prints to ncsim.log)
#include <veriuser.h>

 void pass_string_c(const char* a) {
   io_printf("DPI: %s\n", a);
   // now call exported function
   print_string_c("string passed from C");  // This wont work in IUS583
}

 const char* string_c2v_c(void) {
   io_printf("C: give up a string\n");
   return "Gimme String";
}

-----file: RUN_NC (script)------
rm -r INCA_libs
rm *.so
rm *.log
rm *.h

# Create .h file for Exported tasks/functions only 
# (imported function do NOT need .h file):
ncverilog +sv top.v +ncdpiheader+dpi.h +elaborate +ncelabargs+-messages

# ncvlog -sv top.v -mess
# ncelab top -sv  -dpiheader dpi.h -mess

gcc -fPIC -shared -o main_task.so  main_task.c  -I/`ncroot`/tools/inca/include

ncverilog +sv top.v +sv_lib=main_task.so +access+r +ncsimargs+"-sv_root ./"

----file: ncverilog.log  (IUS6.02)-----------
ncsim> run
DPI: pass it ON
Exported Verilog String=  string passed from C
Verilog: C: give up a string
Gimme String 

Simulation complete via $finish(1) at time 0 FS + 0
./top.v:22  $finish; 
ncsim> exit