bash -- how to judge if a variable is a string or number

Question

In bash shell, how do we judge if a variable is a string or number? Here, number could be an integer or a float. This link "How to judge a variable's type as string or integer" seems to only work integer.

Answer 1

You could expand the proposed regular expression, dependent on the desired number format(s):

[[ $value =~ ^[0-9]+(\.[0-9]+)?$ ]] would recognize 2 or 2.4 as a number but 2. or .4 as a string.

[[ $value =~ ^(\.[0-9]+|[0-9]+(\.[0-9]*)?)$ ]] would recognize all 2, 2.4, 2. and .4 as numbers