Send a running function to background in bash

Question

As the title says, I want to send a running function to the background. Something like

function myfunc { some_command | while read line #some_command must be running indefinitely do #if some condition on ${line} satisfies #Do something and go to background done }

Is it possible?

I know that it is possible to call a function directly & to directly run it in the background. That is pretty obvious. This is not duplicate of this.

Possible duplicate of executing shell command in background from script — Aserre
– Aserre, Commented Jul 24, 2017 at 15:19
Why are you trying to do this? You can call your function form a separated bash script an call this with an ampersand. Then your function is run in the background. — schorsch312
– schorsch312, Commented Jul 24, 2017 at 15:21
Why not while true; do if ...; then do_something & break; fi — William Pursell
– William Pursell, Commented Jul 24, 2017 at 15:31
@WilliamPursell I edited the question. Now it should be clear why I am asking. — Raghuram Vadapalli
– Raghuram Vadapalli, Commented Jul 24, 2017 at 15:39
I don't know if you can send a function to the background. But you surely can send a process or the script to the background. You just need to send an SIGSTOP signal. — Aditya
– Aditya, Commented Jul 24, 2017 at 15:45

Nahuel Fouilleul · Accepted Answer · 2017-07-24 15:59:32Z

A simple command creates a process in background and waits for its termination, in your case the caller must continue when a condition is met asynchronously with callee which continues running.

This can be done with kill -STOP (caller blocks himself) and kill -CONT (callee unblock caller)

function myfunc { some_command | while read line #some_command must be running indefinitely do #if some condition on ${line} satisfies kill -CONT $$ done & kill -STOP $$ }

FYI, the function keyword makes this code needlessly noncompliant with the POSIX sh specification -- it would be portable to a wider array of shells if the first line were myfunc() {, with the function keyword removed and the () syntax added.

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