On Tue, 29 Jun 2021 16:35:28 -0400
Greg Wooledge <g...@wooledge.org> wrote:
> On Tue, Jun 29, 2021 at 01:21:44PM -0700, L A Walsh wrote:
> > I hope a basic question isn't too offtopic.
>
> More of a help-bash question, in my opinion, but close enough.
>
> > Say I have some number of jobs running:
> >
> > > jobs|wc -l
> > 3
>
> OK.
>
> > Would like to pass a varname to njobs to store the answer in, like:
> > > njobs n
> > echo "$n"
> > 3
>
> "How do I pass a value back from a function to its caller, you know,
> like a function in any other programming language can do" is one of the
> holy grails of shell programming. There is no sane answer. You appear
> to be going down the "pass a variable name by reference" path, so:
>
> unicorn:~$ jobs | wc -l
> 3
> unicorn:~$ njobs() { local _n=$(jobs | wc -l); eval "$1=\$_n"; }
> unicorn:~$ njobs walsh
> unicorn:~$ echo "$walsh"
> 3
>
> Now you just need to add sanity-checking on the argument of njobs, to
> avoid whatever code injection the malicious caller wants to perform.
I can't fathom the switch to eval there. Why not printf -v "$1" %s "$_n", for
example? It even rejects invalid identifiers.
--
Kerin Millar
