Re: record stream using time limit, reconnecting as needed

[Roger]

> On Wed, Feb 22, 2023 at 04:21:14PM +0900, Koichi Murase wrote:
>2023???2???22???(???) 12:52 Roger <rogerx.oss@gmail.com>:
>> However, I'm still stumped for how to background an endless loop with the
>> included ffmpeg stream recording, so the stream is easily reconnected if
>> dropped, while falling through to get the PID of the backgrounded endless 
>> loop
>> or ffmpeg, for killing after so many (eg 30) minutes?
>
>If you specify a negative integer (e.g. -<PGID> where <PGID> is an
>integer) to `kill', `kill' will kill all the processes that belong to
>the process group PGID. You can give a distinct process group ID to
>the background while loop by specifying `set -m' before starting the
>background job. Then you can pass the PGID (i.e., the PID of the
>`while' loop) to `kill' to kill all the processes including ffmpeg. In
>this way, you do not need to directly specify the PID of ffmpeg. This
>is an example.
>
>#!/usr/bin/env bash
>
>record() {
>  local -
>  set -m
>  while true; do
>    ffmpeg http://some.url.m3u8
>  done & pgid_task="${!}"
>}
>
>sleep_while_recording() { sleep 30m; }
>
>record
>sleep_while_recording
>kill -INT -"$pgid_task"

I worked on this for awhile and found the following was required for killing a 
PGID/process group:

kill -- -$(ps -o pgid=$pgid_task | grep [0-9] | tr -d ' ')

Cannot remember the reason why "kill -- -$pgid_task" was not working, something 
about the variable not reliable passing back a list of PIDs, as such, ps -o was 
required, along with ensuring no white space was included.

Frankly, kill prints a really ugly non-zero return upon script exit.

I'm not seeing a signal emulating a safe return 0 exit, likely for good reason.

Although this method is likely far more reliable, as long as a file number 
suffix is incremented upon each loop for preventing file over-writing, later 
concating the files as needed; thinking of now trying the ffmpeg -reconnect 
method.

Think I also had to globally declare (eg. "declare -g pgid_task") pgid_task 
also.

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