bash: `set +m` option does not work when placed in the .bashrc file

Question

If I enter the command:

set +m

at the end of the .bashrc file, when I run the command:

echo $-

the option m is missing as it should be, but...

If I enter the command:

{ sync & } 2> /dev/null

and then I press enter again without entering any commands, although I removed the m option, the output still appears:

[1]+  Done                    sync

and only when I rerun the command from the terminal:

set +m

then the output is no longer shown. In other words, this command has effect only if executed from the terminal.

The question is:

How do I make it work when placed in .bashrc file?

Answer 1

Got it!.. It will work if you put it in as export PROMPT_COMMAND='set +m'. You could use set -o monitor also.

This probably needs a bug report. I found one for Cygwin: https://cygwin.cygwin.narkive.com/PdJFe7Q6/bash-monitor-mode-remains-enabled-if-disabled-in-bashrc