checking if a string is a palindrome

Question

I am trying to check if a string is a palindrome in bash. Here is what I came up with:

#!/bin/bash
read -p \"Enter a string: \" string
if [[ $string|rev ==         


        

Answer 1

A bash-only implementation:

is_palindrome () { 
    local word=$1
    local len=$((${#word} - 1))
    local i
    for ((i=0; i <= (len/2); i++)); do
        [[ ${word:i:1} == ${word:len-i:1} ]] || return 1
    done
    return 0
}

for word in hello kayak; do
    if is_palindrome $word; then
        echo $word is a palindrome
    else
        echo $word is NOT a palindrome
    fi
done

Inspired by gniourf_gniourf:

is_palindrome() {
  (( ${#1} <= 1 )) && return 0
  [[ ${1:0:1} != ${1: -1} ]] && return 1
  is_palindrome ${1:1: 1}
}

I bet the performance of this truly recursive call really sucks.