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.
And maybe consider adding "make sure $1 isn't _n" to the list of your
sanity checks, since the caller can't be permitted to use that particular
variable name.
unicorn:~$ njobs _n
unicorn:~$ echo "$_n"
(At least it didn't go into an infinite loop!)
