BASH Palindrome Checker

Question

This is my first time posting on here so bear with me please.

I received a bash assignment but my professor is completely unhelpful and so are his notes.

Our assig

Answer 1

Why use grep? Bash will happily do that for you:

#!/bin/bash

is_pal() {
    local w=$1
    while (( ${#w} > 1 )); do
        [[ ${w:0:1} = ${w: -1} ]] || return 1
        w=${w:1:-1}
    done
 }

 while read word; do
     is_pal "$word" && echo "$word"
 done

Save this as banana, chmod +x banana and enjoy:

./banana < /usr/share/dict/words

If you only want to keep the words with at least three characters:

grep ... /usr/share/dict/words | ./banana

If you only want to keep the words that only contain lowercase and have at least three letters:

grep '^[[:lower:]]\{3,\}$' /usr/share/dict/words | ./banana