SQL Retrieve system name by MI call

system_name.sql

-- Retrieve the system name by call to MI  
-- This also showcase how to integrate the C code directly into your UDTF
--
-- Simply paste this gist into ACS SQL and step through the example.
--
-- It is a cool example how far you can go with SQL: Have fun 😀  
-- (C) Niels Liisberg 2022
--
-- This gist is distributed on an "as is" basis, without warranties 
-- or conditions of any kind, either express or implied.
----------------------------------------------------------------------------------------------
call qsys2.ifs_write(
    path_name => '/tmp/main.c' , 
    file_ccsid => 1208, 
    overwrite => 'REPLACE',
    line =>'
{
    #include <QSYSINC/MIH/MATMATR>

    _MMTR_Template_T template;                                      
    short attr = _MMTR_APPN;                                        
                                                                    
    template.Options.Template_Size = sizeof(_MMTR_Template_T);      
    _MATMATR1 (&template , &attr );                              
    memcpy (                                                        
        MAIN.OUTPUT,    
        template.Options.Data.APPN.Sys_Name ,                        
        template.Options.Data.APPN.Name_Len                       
    );                                                              

} 
');

create or replace function qusrsys.system_name () 
returns varchar (10)
set option output=*print, commit=*none, dbgview = *source --list
main:begin
    
    declare output char(10) for bit data default '';
    include '/tmp/main.c';
    return rtrim(output);
end;

-- unit test 
values ( 
   qusrsys.system_name  ()                                                                                                                    
);