Something

[hq4ever@maxim-ws InitScripts]$ cat trapsh.sh
#!/bin/bash
set -x


trap "echo retval = $?" ERR

echo "pid is $$"

while :                 # This is the same as "while true".
do
        sleep 5 # This script is not really doing anything.
        mount /home/king
done
[hq4ever@maxim-ws InitScripts]$
[hq4ever@maxim-ws InitScripts]$
[hq4ever@maxim-ws InitScripts]$ ./trapsh.sh
+ trap 'echo retval = 0' ERR
+ echo 'pid is 735'
pid is 735
+ :
+ sleep 5
+ mount /home/king
mount: can't find /home/king in /etc/fstab or /etc/mtab
++ echo retval = 0
retval = 0
+ :
+ sleep 5

[hq4ever@maxim-ws InitScripts]$ mount /home/king
mount: can't find /home/king in /etc/fstab or /etc/mtab
[hq4ever@maxim-ws InitScripts]$ echo $?
1