Bash script not exiting immediately when `exit` is called

Question

I have the following bash script:

tail -F -n0 /private/var/log/system.log | while read line 
do
    if [ ! `echo $line | grep -c 'launchd'` -eq 0 ]; then
        echo 'launchd message'
        exit 0
    fi
done

For some reason, it is echoing launchd message, waiting for a full 5 seconds, and then exiting.

Why is this happening and how do I make it exit immediately after it echos launchd message?

Answer 1

Since you're using a pipe, the while loop is being run in a subshell. Run it in the main shell instead.

#!/bin/bash

while ...
do
   ...
done < <(tail ...)