Expand alphanumeric range from variable in bash

May 16, 2023

I have a variable which contains two alphanumeric sequences separated by a hyphen. I need to expand these to the full inclusive range separated by spaces. Here are some examples to illustrate:

0-9     -> 0 1 2 3 4 5 6 7 8 9
a-h     -> a b c d e f g h
B-Z     -> B C D E F G H I J K L M N O P Q R S T U V W X Y Z
95-101  -> 95 96 97 98 99 100 101

These match bash brace expansion format, so I was looking to use this e.g. {0..9}, but I can’t find a way to put variables in the expansion. I can get each side of the expansion, and using seq I can expand the numeric ones, but haven’t found a way to expand the alphabetic sequences.

Any solution is fine, whether it uses bash brace expansion, manually separates the sides and expands them through another function, or does anything else.

>Solution :

With ksh, can be run in a subshell in bash:

#!/bin/bash

x=0-9

read -ra digits < <(
    ksh -c '
        range=$1
        exp={$range}
        echo ${exp/-/..}
    ' ksh $x
)
printf '%s\n' "${digits[@]}"

Will work with alphabetic characters too.