UNIX for Dummies Questions & Answers

hi all, I have read similiar topics in this board, but i didn' t find the posting which is the same with the problem i face.. I try to extract string from the end. i try to do this:

num=abcdefghij
num2=${num:-5}
echo $num2 #this should print the last 5 characters (fghij)
but it doesn;t work.. the error message appears: 0403-011 The specified substitution is not valid for this command.

Code:

num=abcdefghij
num2=$(echo $num | sed 's/.*\(.\{5\}\)$/\1/')
echo num2

One way:

$ num=abcdefghij
$ num2=${num#${num%?????}}
$ echo $num2
fghij
$

thanks bro.. it works.....