When do we need curly braces around shell variables?

Question

In shell scripts, when do we use {} when expanding variables?

For example, I have seen the following:

var=10        # Declare variable

         


        

Answer 1

You are also able to do some text manipulation inside the braces:

STRING="./folder/subfolder/file.txt"
echo ${STRING} ${STRING%/*/*}

Result:

./folder/subfolder/file.txt ./folder

or

STRING="This is a string"
echo ${STRING// /_}

Result:

This_is_a_string

You are right in "regular variables" are not needed... But it is more helpful for the debugging and to read a script.