Re: while do done

On Fri, 02 Jul 2021 14:16:20 +1000, Reuben ua =?UTF-8?Q?Br=C3=AD=C4=A1?= wrote:

> you CAN interrupt
>
> while do sleep 0; done
>
> there is no need for exit, and it doesnt fix
>
> while do done
>
> or
>
> while :; do :; done
>
> if your shell needs something to not do.

Actually, the following _can_ be interrupted:

while :; do done

while :; do :; done

The only problem is:

while do done

which may not actually be valid syntax.

I checked some other bourne/korn-like shells:

dash:
$ while do done
sh: 1: Syntax error: "do" unexpected

AT&T ksh:
$ while do done
ksh: syntax error: `do' unexpected

bash:
bash-5.1$ while do done
bash: syntax error near unexpected token `do'

zsh:
% while do done
[CPU loop like OpenBSD ksh]

I think the proper fix here is to reject the empty while in OpenBSD's
sh/ksh.

- todd