grep causes EXIT trap in bash script [closed]

Question

When running the following script in OSX using bash version 3.2

#!/bin/sh

set -e
function _trap_exit {
   echo "this is a triggered trap..."
}

trap _trap_exit EXIT

/usr/sbin/ioreg -w0 -l | grep ExternalChargeCapable | grep -q No

echo "Final statement"

I get a trap triggered. But if I change the final grep statement to Yes ie grep -q Yes then the trap isn't triggered.

Any idea why this is happening and how to stop it? Why should the exit code from grep cause a trap to be triggered?

Answer 1

From Bash man page...

-e      Exit immediately if a simple command (see SHELL GRAMMAR above) exits with a non-
        zero  status.   The shell does not exit if the command that fails is part of the
        command list immediately following a while or until keyword, part of the test in
        an  if  statement,  part of a && or || list, or if the command's return value is
        being inverted via !.  A trap on ERR, if  set,  is  executed  before  the  shell
        exits.

[/Slapshead]

Sorry to have wasted your time...