Bash Script: Alphabetize strings without using -sort

Question

I'm trying to alphabetize three strings and then concatenate them together. So for example if I have:

a="zebra"
b="ape"
c="fox"

I should end up with apefoxzebra

I need to do with WITHOUT using sort.

Here's what Ive been trying to alphabetize the strings, but it doesn't seem to be sorting right. It just picks 'a' every time.

a="zebra"
b="aardvark"
c="cat"


if [[ "$a" -le "$b" && "$a" -le "$c" ]]; then
    first=$a

elif [[ "$b" -le "$a" && "$b" -le "$c"  ]]; then
        first=$b
    else
         first=$c
fi

Answer 1

Thanks to @gniourf_gniourf for the answer!

-le is for arithmetic comparison. To compare strings lexicographically, use < .