[SQLPLUS] How to get the number of returned rows?

Question

Oracle

I have a batch pipeline function called in SQLPLUS that writes the result (table) to a file.
I need to additionally count the number of returned rows, and if nothing is returned, then exit the script with an error code.

WHENEVER oserror exit 1;
WHENEVER sqlerror exit 2;
SET HEADING OFF
SET FEEDBACK OFF
SET PAGESIZE 0
SET ECHO OFF
SPOOL ./tmp/retTables.txt
SELECT * FROM TABLE(usr.util_pack.Get_List);
SPOOL OFF;
exit 0;

I have no idea how to count the lines, and that they would not fall into the resulting file.