Re: simple prob?

[Alex fxmbsw7 Ratchev]

jobsn=( $( jobs -p ) ) jobsn=${jobsn[@]}

On Fri, Jul 2, 2021, 09:10 Phi Debian <phi.debian@gmail.com> wrote:

> On Tue, Jun 29, 2021 at 10:23 PM L A Walsh <bash@tlinx.org> wrote:
>
> > I hope a basic question isn't too offtopic.
> > Say I have some number of jobs running:
> >
> > >  jobs|wc -l
> > 3
> > ---
> >
> > Would like to pass a varname to njobs to store the answer in, like:
> >
> > So I can run:
> >
> > >  njobs n
> > echo "$n"
> > 3
> >
> >
> This a a double question 'how to', and I see no bash bugs here.
>
> The 2 questions are
> - how do I pass a variable name as an output argument to a function ('n' in
> your 'jobs n' example)
> - how to set a variable in a sub command? that is no doable, a sub command
> can't return variable to its parent, so you obviously have to do things
> diffrently.
>
> A simple 2 liners, solve all this, with no code injection blah....
>
>
> PW$ jobs
> [1]   Running                 sleep 11111111111 &
> [2]   Running                 sleep 11111111111 &
> [3]-  Running                 sleep 11111111111 &
> [4]+  Running                 sleep 11111111111 &
>
> PW$
>
> PW$ function njobs
> > { [ "$1" != "n" ] && typeset -n n="$1"
> >    typeset -a t ; readarray t <<<"$(jobs)" ;n=${#t[@]}
> > }
>
> PW$ njobs n ; echo $n
> 4
>
> # explanations (you may skip here)
> #===========================
> [ "$1" != "n" ] && typeset -n n="$1"
> This make sure the given output variable name is a valid SHELL identifier,
> providing anything not valid in "$1" will break there.
> This also enforce that the given $1 output variable name doesn't match our
> own local nameref name, if it match we don't do our nameref, and re-use the
> upper scope output variable name, that by definition is a valid variable
> name if we got that far.
>
> typeset -a t
> define a local array that we will fill, being local mean the booking is
> done at function return
>
> readarray t <<<"$(jobs)" ;
> Fill the array with your command you want to count lines for.
>
> n=${#t[@]}
> Fill the output variable
>
> All is safe, all is clean, no 'apparent' temp file, no sub command :)
>
> Shell programing is fun :)
>