StackOverflow (PT) — 361627

for i in $(seq 0 492); do
    filename=$(printf %04d $i)

    opencv_createsamples -img toras/toras_$filename.jpg \
    -bg negativas/negativas.txt \
    -info positivas$i/positivas$i.txt \
    -maxxangle 0.5 \
    -maxyangle 0.5 \
    -maxzangle 0.5 \
    -num 100 \
    -bgcolor 0
done