Print all the substrings of a string in Bash

example.txt

$ ./substrings.bash '1234567890' 133
1234567890
$ ./substrings.bash '1234567890' 10
1234567890
$ ./substrings.bash '1234567890' 9
1234567890
123456789
234567890
$ ./substrings.bash '1234567890' 8
1234567890
123456789
234567890
12345678
23456789
34567890
$ ./substrings.bash '1234567890' 7
1234567890
123456789
234567890
12345678
23456789
34567890
1234567
2345678
3456789
4567890
$ ./substrings.bash '1234567890' 1
1234567890
123456789
234567890
12345678
23456789
34567890
1234567
2345678
3456789
4567890
123456
234567
345678
456789
567890
12345
23456
34567
45678
56789
67890
1234
2345
3456
4567
5678
6789
7890
123
234
345
456
567
678
789
890
12
23
34
45
56
67
78
89
90
1
2
3
4
5
6
7
8
9
0

substrings.bash

#!/usr/bin/env bash
# Periklis Ntanasis <pntanasis@gmail.com> - 2019

# Prints all the substrings of the given string ("word") up to a minimum length ("min_length").
function getSubstrings {
	local word=$1
	local length=${#1}
	local min_length=$2
	local remove=0
	local retval=()
	
	if [[ $min_length -gt $length ]]; then
		min_length=$length
	fi

	while [ $remove -lt $length ]; do
		start=0
		len=$(($length-$remove))
		if [[ len -lt min_length ]]; then
			exit
		fi
		while [ $(($start+$len)) -le $length ]; do
			substring=${word:$start:$len}
			echo $substring
			start=$(($start+1))
		done
		remove=$(($remove+1))
	done
}

getSubstrings $1 $2