Re: simple prob?

[Greg Wooledge]

On Tue, Jun 29, 2021 at 02:05:46PM -0700, L A Walsh wrote:
>    That would be 'me', so I'm going to rule out malicious
> code injection! :-), but that's also why I used printf to
> write the output, the worst that could happen is some varname
> is overwritten with the answer, no?

Sadly, this is not correct.  You can still get code injections with
printf -v.

unicorn:~$ njobs2() { printf -v "$1" %s 42; }
unicorn:~$ njobs2 'x[0$(date >&2)]'
Tue Jun 29 17:00:29 EDT 2021

> Simpler -- don't use a variable:
> 
>   njobs() { printf ${1:+-v $1} "%s\n" "$(jobs |wc -l)"; }

You're adding a newline to the variable.  That may not be what you want.

> So...hmmm...how is it that jobs picks up the right answer in what
> would seem to be a subshell?  Special cased?

The subshell inherits the job list from its parent -- it just can't
*wait* for any of those jobs, since it isn't their parent.  But it can
still count them.