How to extract all datafile names without path using substr and instr functions

select trim(
            substr(file_name,
                (instr(file_name,'/', -1, 1) +1)
                )
               )  "file name"
from  dba_data_files;

Result:

file name
system01.dbf
sysaux01.dbf
undotbs01.dbf
users01.dbf
appl_data.dbf