The PID of a backgrounded child process is stored in $!
, and the current process is $$
:
fpfunction &
child_pid=$! # in parent process, child's pid is $!
parent_pid=$$ # in parent process, parent's pid is $$
When in the backgrounded function, the child processes’s PID is $BASHPID
rather than $$
, which is now the parent’s PID:
fpfunction() {
local child_pid=$BASHPID # in child process, child's pid is $BASHPID
local parent_pid=$$ # in child process, parent's pid is $$
...
}
Also for what it’s worth, you can combine the looping statements into a single C-like for loop:
for ((n = 1; n < 20; ++n)); do
echo "Hello World-- $n times"
sleep 2
echo "Hello World2-- $n times"
done