Why am I getting this 'bad substitution' error in my bash command?

Question

when I run this I get this \'bad substitution\' error. What can I do?

$ x=\"Hello World\"
$ echo \"$x\"
Hello World
$ echo \"${x^^}\"
-bash: ${x^^}: bad subs         


        

Answer 1

Your method only works in bash 4. Try this:

echo $x | tr '[a-z]' '[A-Z]'