convert last character of a string to upper case

Question

How can I convert last character of the string to upper case ?

ex:

foo=test
echo ${foo^}

this works for first character

Test 

I want the output to be

TesT

How does this work?

Answer 1

Using GNU sed:

foo=test
sed 's/.$/\U&/' <<< "$foo"

Using an extra variable:

foo=test
tmp="${foo: -1}"
echo "${foo:: -1}${tmp^}"