Find palindrome without loops using sed

Question

I would like to determine if a string is palindrome or not.
Let's say that I have file like this:
abcccba
abcccccccccccccccccccccccba

alfabetaalfa

I would like to check every line of this file and say "PALINDROME" every time line is a palindrome. The problem is i cannot use matching like ([0-9])([0-9])/2/1 because i dont know how long the word will be. I think that i should patternbuffer somehow.

Searching stackoverflow to find some hints, i have found this: sed -r 'h;s/[^[:alpha:]]//g;H;x;s/\n/&&/;ta;:a;s/\n(.)\n(.)/\n\2\1\n/;ta;G;/\n(.)\n\n\1$/I;d' $1

The problem is that it does not exactly work as it should and I have no idea how to use it to print specific words like "PALINDROME" or "NOT A PALINDROME".

Thank you so much for any help.

EDIT: of course by "not using loops" i mean common loops. Jumping to labels is okay.

Answer 1

You don't have to use sed:

xxx="rrrtttrrr"

if [ $xxx == `echo $xxx| rev` ]; then
    echo "PALINDROME"
else
    echo "NOT A PALINDROME"
fi

Sed version could be found here:

#! /bin/sed -f
# Laurent Le Brun <laurent [at] le-brun.eu> - 2007

:loop
s/^\(.\)\(.*\)\1$/\2/
t loop
/...*/ {
    i\
 no
    b end
}  
i\
 yes

:end
d