These scripts are useful to turn on and off SQL Trace.These scripts will display the trace file created and its location!
These scripts contain useful SQL*Plus scripting techniques.
from SQL*Plus:

SQL> start start_trace
SQL>  ...run your test/application here
SQL> start stop_trace
...to trace another session...use these scripts...follow the prompts...
SQL> start start_trace_in_session
SQL>  ...run your test/application here
SQL> start stop_trace_in_session