Daemon won't kill children that are reading from a named pipe - linux

Question

I've written this bash daemon that keeps an eye on a named pipe, logs everything it sees on a file named $LOG_FILE_BASENAME.$DATE, and it also creates a filtered version of it in $ACTIONABLE_LOG_FILE:
while true
do
DATE=`date +%Y%m%d`
cat $NAMED_PIPE | tee -a "$LOG_FILE_BASENAME.$DATE" | grep -P -v "$EXCEPTIONS" >> "$ACTIONABLE_LOG_FILE"
done
pkill -P $$ # Here it's where it should kill it's children
exit 0
When the daemon is running, this is how the process table looks:
/bin/sh the_daemon.sh
\_ cat the_fifo_queue
\_ tee -a log_file.20150807
\_ grep -P -v "regexp" > filtered_log_file
The problem is that when I kill the daemon (SIGTERM), the cat, the tee, and the grep processes that where spawned by the daemon are not collected by the parent. Instead, they become orphans and keep on waiting for input on the named pipe.
Once the FIFO receives some input, then they process that input as instructed and die.
How can I make the daemon kill its children before dying? Why aren't they dying with pkill -P $$?

Answer 1

You want to setup a signal handler for your script which kills all members of its process group (its children) in case the script itself gets signalled:
#!/bin/bash
function handle_sigterm()
{
pkill -P $$
exit 0
}
trap handle_sigterm SIGTERM
while true
do
DATE=`date +%Y%m%d`
cat $NAMED_PIPE | tee -a "$LOG_FILE_BASENAME.$DATE" | grep -P -v "$EXCEPTIONS" >> "$ACTIONABLE_LOG_FILE"
done
handle_sigterm
exit 0
Update:
As per pilcrow's comment replace
cat $NAMED_PIPE | tee -a "$LOG_FILE_BASENAME.$DATE" | grep -P -v "$EXCEPTIONS" >> "$ACTIONABLE_LOG_FILE"
by
cat $NAMED_PIPE | tee -a "$LOG_FILE_BASENAME.$DATE" | grep -P -v "$EXCEPTIONS" >> "$ACTIONABLE_LOG_FILE" &
wait $!