Checking for numeric arguments

Question

I want to check function arguments, and check whether $2 and $3 are numeric Is the following line the way to use the AND statement? Am I using = the correct way to check for numeric digits?

if [[ "$2" = +([[:digit:]]) ]] && [[ "$3" = +([[:digit:]]) ]]; then

Always paste your script into https://shellcheck.net, a syntax checker, or install shellcheck locally. Make using shellcheck part of your development process. — waltinator, Nov 17 '21 at 05:32
Also, what you really want to match is: <1 or more digits>. What you have matches a string with a digit in it. Test cases: "a1a", "1a", "129" — waltinator, Nov 17 '21 at 05:36
Does this answer your question? Checking if an input number is an integer — Kusalananda, Nov 17 '21 at 07:48
@waltinator It is not so. "a1a" returns false, whilst "123" returns true. — Vera, Nov 17 '21 at 14:54
I do get confused on whether to use = or ==. Is there any general rule? — Vera, Nov 17 '21 at 15:18

score 1 · Answer 1 · answered Nov 17 '21 at 05:34

I suggest creating a function, perhaps called "IsInt", which returns true if the parameters passed is numeric. You would then say

if IsInt "$2" && IsInt "$3" ; then
...
fi

You then have the simpler task of creating "IsInt", or looking at an existing answer

Checking for numeric arguments

1 Answers1