Bash function for zero length string or with whitespace

Question

In bash I can use -z string and -n string to see if the string length is zero or not. Would like to write a bash function that returns true or false, not only if length is zero but also if it is all whitespace. Or is there a way without needing a function?

Answer 1

You can use a regular expression:

if [[ $string =~ ^" "*$ ]]

or you can remove all the spaces before testing with -z:

if [[ -z "${string// /}" ]]