Cannot debug simple ksh programme

Question

I wrote this sample KornShell (ksh) code but it is getting bad substitution error during the if clause.

while ((i < $halflen))
do
 if [[${strtochk:i:i}==${str         


        

Answer 1

You are using ksh88 but the code you tried is using ksh93 feature missing for the 88 version.

You need to replace

if [[${strtochk:i:i}==${strtochk:j:j}]];then

with these portable lines:

if [ "$(printf "%s" "$strtochk" | cut -c $i)" =
     "$(printf "%s" "$strtochk" | cut -c $j)" ]; then

and the incorrect:

i++
j--

with:

i=$((i+1))
j=$((j-1))