Re: "printf %d ''" should diagnose the empty string

[Lawrence Velázquez]

On Mon, Feb 10, 2025, at 2:24 PM, Phi Debian wrote:
> On Mon, Feb 10, 2025 at 5:48 PM Chet Ramey <chet.ra...@case.edu> wrote
>
>>
>> There isn't a reward for brevity or obfuscation; say what you mean:
>>
>> isnum2()
>> {
>>         case "$1" in
>>         [-+] | '')      return 1;;      # empty or bare `-' or `+'
>>         [-+]*[!0-9]*)   return 1;;      # non-digit with leading sign
>>         [-+]*)          return 0;;      # OK
>>         *[!0-9]*)       return 1;;      # non-digit
>>         *)              return 0;;      # OK
>>         esac
>> }
>>
>> It obviously doesn't handle 0x constants, but could be changed to.
>>
>
> Would you  accept this one then, should be general enough, faster too, and
> explicit, really mean what is accepted as num literal
>
> $ echo $BASH_VERSION
> 5.2.21(1)-release
> $ function isanum
> { (($1)) || (($1==0))  && return 0
>   return 1
> }  >/dev/null 2>&1

This accepts many valid expressions, not just literals.

        % cat /tmp/isnum.bash
        chet() {
                case $1 in
                        [-+] | '') return 1 ;;
                        [-+]*[!0-9]*) return 1 ;;
                        [-+]*) return 0 ;;
                        *[!0-9]*) return 1 ;;
                        *) return 0 ;;
                esac
        }

        phi() {
                (($1)) || (($1==0))
        }

        chet '1+2'
        printf 'chet 1+2 -> %s\n' "$?"

        phi '1+2'
        printf 'phi 1+2 -> %s\n' "$?"

        % bash /tmp/isnum.bash
        chet 1+2 -> 1
        phi 1+2 -> 0

-- 
vq