Expected output if input is comma separated:
1
5
7
Expected output if input is space separated:
1
5
7
Expected output if input is - and , separated:
1
2
3
5

input_string="1,5,7"
IFS=' ' read -r -a array <<< "$input_string"
echo ${array[1]} etc..

input_string="1 5 7"
 read -r -a array <<< "$input_string"
echo ${array[1]} etc..

$ cat ranges.sh
#!/bin/bash
IFS=', ' read -a ranges <<< "$*"
for range in "${ranges[@]}"; do
        IFS=- read start end <<< "$range"
        [ -z "$start" ] && continue
        [ -z "$end" ] && end=$start
        for (( i=start ; i <= end ; i++ )); do
                echo "$i"
        done
done
$ bash ranges.sh 1-3,5 9-10
1
2
3
5
9
10