Re: Best way to expand a boolean into a string when true

Le mar. 3 mars 2026 à 02:15, Martin D Kealey <[email protected]> a écrit :
>
> I suggest that the preface text be removed, and the four following paragraphs be amended to read something like:
>
> ${parameter-word} or ${parameter:-word}
> Use Default Values.
> If parameter is unset (or set but null, if the colon is included), the expansion of word is substituted. Otherwise, the value of parameter is substituted.
> ${parameter=word} or ${parameter:=word}
> Assign Default Values.
> If parameter is unset (or set but null, if the colon is included), the expansion of word is assigned to parameter. The value of parameter is then substituted. Positional parameters and special parameters may not be assigned to in this way.
> ${parameter?word} or ${parameter:?word}
> Display Error if Null or Unset.
> If parameter is unset (or set but null, if the colon is included), the expansion of word (or a message to that effect if word is not present) is written to the standard error and the shell, if it is not interactive, exits. Otherwise, the value of parameter is substituted.
> ${parameter+word} or ${parameter:+word}
> Use Replacement Value.
> If parameter is unset (or set but null, if the colon is included), nothing is substituted, otherwise the expansion of word is substituted.
>
> Alternatively, remove the preamble paragraph and add this paragraph as the 5th entry in the list:
>
> ${parameter-word}
> ${parameter=word}
> ${parameter?word}
> ${parameter+word}
> These function the same as the corresponding colon variants, except that they check only for the parameter being unset; being set but null is treated the same as being set to any other value.
>
> -Martin
>
> PS: Whilst the English meaning of “null” can be “empty”, in computing it's commonly used to mean “absence of an object” as distinct from “empty object”, so I would avoid, but I would leave that as a change for another day.

I also think such a wording would be clearer.

Best regards,
    Laurent