test.sh

#!/bin/sh
export COUNTER=0

mkdir -p filesrenamed

for f in CREDIT_RATING_PREV_*; do result=$(mv $f ${f/${f:0:19}/CREDITRATING_T3_}) ; ((COUNTER++)); done  2> /dev/null

# exit status https://pubs.opengroup.org/onlinepubs/7908799/xcu/mv.html

# v rámci toho for cyklu bych dal podmínku - napíšu to zvlášt ale ty to musíš dát do for

var ok=0
if [ $result -eq 0 ]
then
  ok ++
fi