Question

This statements works fine in BASH v. 4.1.7(1), but not in BASH v. 4.2.20(1)

num=${number:$counter:1}

I am getting “Bad Substitution” as the error. Any insights on why this is happening?
The objective is to do something similar to ${string:position:length} for getting sub-string.

Any help will be much appreciated. Thanks.

The original code which had this line is added below (line 15)

#!/bin/bash

echo "Please enter a number: "
read number

counter=0
answer=0
end=$(( ${#number} - 1 ))

echo -n "The sum of all digits of "
echo -n $number
echo -n " is "

while [ $counter -lt ${#number} ] ; do
num=${number:$counter:1}
if [ $counter -lt $end ] ; then
echo -n $num
echo -n "+"
else
echo -n $num
echo -n "="
fi
answer=$(( $answer + $num ))
counter=`expr $counter + 1`
done

echo $answer

Answer 1

the expression is fine with 4.2.20 when i tested it. maybe you have something in your env?

[localhost ~]$ bash --version
GNU bash, version 4.2.20(1)-release (i386-redhat-linux-gnu)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
[localhost ~]$ number=123
[localhost ~]$ counter=0
[localhost ~]$ echo $number
123
[localhost ~]$ num=${number:$counter:1}
[localhost ~]$ echo $num
1