Questions[scripting](server)

Try executing the following under a bash shell echo "Reboot your instance!"

On my installation:

root@domU-12-31-39-04-11-83:/usr/local/bin# bash --version
GNU bash, version 4.1.5(1)-release (i686-pc-linux-gnu)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
root@domU-12-31-39-04-11-83:/usr/local/bin# uname -a
Linux domU-12-31-39-04-11-83 2.6.35-22-virtual #35-Ubuntu SMP Sat Oct 16 23:57:40 UTC 2010 i686 GNU/Linux
root@domU-12-31-39-04-11-83:/usr/local/bin# echo "Reboot your instance!"
-bash: !": event not found

Can anyone please explain what is "bash events?" I've never heard this concept before. Also, how should I output "!" at the end of the sentence?

I just wondered what exactly the difference between

[[ $STRING != foo ]]

and

[ $STRING != foo ]

is, apart from that the latter is POSIX-compliant, found in sh and the former is an extension found in bash.

For example, I have a simple bash file

#!/bin/bash
cd ~/hello
ls

How can I make it display every command before executing it? Just the opposite effect of "@echo off" in windows batch scripting.

I have a scheduled task that starts a batch script that runs robocopy every hour. Every time it runs a window pops up on the desktop with robocopy's output, which I don't really want to see.

I managed to make the window appear minimized by making the scheduled job run

cmd /c start /min mybat.bat

but that gives me a new command window every hour. I was surprised by this, given cmd /c "Carries out the command specified by string and then terminates" - I must have misunderstood the docs.

Is there a way to run a batch script without it popping up a cmd window?

What is the best way to determine if a variable in bash is empty ("")?

I have heard that it is recommended that I do if [ "x$variable" = "x" ]

Is that the correct way? (there must be something more straightforward)