I just can't figure out how do I make sure an argument passed to my script is a number or not.
All I want to do is something like this:
test *isnumber* $1 && VAR=$1 || echo "need a number"
Any help?
One approach is to use a regular expression, like so:
re='^[0-9]+$'
if ! [[ $yournumber =~ $re ]] ; then
echo "error: Not a number" >&2; exit 1
fi
If the value is not necessarily an integer, consider amending the regex appropriately; for instance:
^[0-9]+([.][0-9]+)?$
...or, to handle numbers with a sign:
^[+-]?[0-9]+([.][0-9]+)?$