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shellfish

In fish shell how to check if a variable is a number?

How to check if a variable is a number in fish shell? Looking for a simple way of doing it.

Solution

  • One possible solution is using string match as follows:

    for arg in 9 -42 0 3.14159 stack overflow hyphenated-word 922-99999 0...0 555.555.555
    if string match -qr '^-?[0-9]+(\.?[0-9]*)?$' -- "$arg"
        echo $arg is a number
    end
end

9 is a number
-42 is a number
0 is a number
3.14159 is a number

    If num is not a number nothing is echo-ed.

    Here's string match synopsis from fish shell documentation (https://fishshell.com/docs/current/commands.html#string):

    string match [(-a | --all)] [((-e | --entire)] [(-i | --ignore-case)] [(-r | --regex)]
         [(-n | --index)] [(-q | --quiet)] [(-v | --invert)] PATTERN [STRING...]