substring

#!/bin/bash

zeroToNine=0123456789

echo ${zeroToNine:0}
# 0123456789

echo ${zeroToNine:7}
# 789

echo ${zeroToNine:5:4}
# 5678

echo ${zeroToNine: -3}
# 789

echo ${zeroToNine: -6: 2}
# 45

echo ${zeroToNine: -4:-1}
# 678

array=(0 1 2 3 4 5 6 7 8 9)
echo ${array[@]:4:3}
# 4 5 6