exit on error in shellscript

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set -e: Enables checking of all commands. If a command exits with an error and the 
caller does not check such error, the script aborts immediately. Enabling this will 
make your scripts more robust. But don't wait until your script is "complete" to set 
the flag as an afterthought, because it will be a nightmare to fix the scrip to work 
with this feature enabled. Just write set -e as the very first line of your code; 
well... after the shell bang.

set -x: If you are writing simple scripts that are meant to, well, script the execution 
of a few tasks (as opposed of being full-flown programs written in shell), set this 
flag to trace the execution of all commands. This will make the interpreter print 
each command right before it is executed, so it will aid you in knowing what is 
happening at any point in time.