I wish it were that simple a case. Turns out there are other cases where a
script that runs well in non-interactive move would crash when run with -i.
In my case it was trap for TSTP. A workaround is to put ``setopt
nomonitor``, which in my case is valid as I don't need job control. Though
what is interesting is that the script ends with an error code of 0. Anyway
the exit behavior itself is inconsitent. Try two experiments: 1) add ``trap
'foo=1' TSTP`` as first line of your sample code in this thread. This time
zsh would complain but not exit. 2) add ``trap 'foo=1' TSTP`` to your
function read-field() or in while loop. This time zsh will exit with error
code 1. In my script, where the trap is somewhere in 3 or 4th level
function in the stack, the script exits with exit code 0.

Here's the link to relevant part of code:
https://github.com/zsh-users/zsh/blob/b1533066ca7d50c88b37ce72093c12cf19807818/Src/signals.c#L921-L924
```
    if (jobbing && (sig == SIGTTOU || sig == SIGTSTP || sig == SIGTTIN)) {
        zerr("can't trap SIG%s in interactive shells", sigs[sig]);
        return 1;
    }
```

I figured ``setopt nomonitor`` disables jobbing, and bypasses executing
that if block.

On Mon, Feb 13, 2023 at 1:43 AM Roman Perepelitsa <
roman.perepelitsa@gmail.com> wrote:

> On Mon, Feb 13, 2023 at 9:57 AM OG Code Poet <ogcodepoet@gmail.com> wrote:
> >
> > My larger script misbehaves and exits with 0 before it could
> > complete if I replace #!/usr/bin/env zsh with #!/usr/bin/env -S zsh
> > -fi or #!/usr/bin/env -S zsh -i.
>
> You might want to try to figure out why.
>
> > Is there a restriction on starting any existing functional zsh
> > program with -fi? Put another way, are all non-interactive shell
> > scripts guaranteed to function when shebang is changed to
> > #!/usr/bin/env -S zsh -fi??
>
> If you put something like this in a script, it won't work the same way
> in interactive shell:
>
>     [[ -o interactive ]] && exit
>
> In general, if your script needs interactive features, it makes
> perfect sense to use an interactive shell as the interpreter.
>
> Roman.
>