Um exemplo de loop aninhado
samples="sample01 sample02 sample03"
for s in ${samples}
do
cat ${s}_id1.txt ${s}_id2.txt > ${s}_id12.txt
for ((t=17, i=1; t<43; t=t+2, i++))
do
echo "[$i] Iteration - t = $t"
unique.py -o count.txt -t $t ${s}_id12.txt
done
done