Friday, 12 May 2017

Shell Script stuff in Linux

I've wanted to make up a simple script that runs an update on my desktop and then either shuts down, reboots or continues depending on what parameters I add to the end.

Something like;

update reboot

update shutdown

or just update to install the updates and do nothing else.

I managed this with good old DOS many years ago and started to look up how to do this with Linux, I have to say that the vast majority of instructions are based up using foo and bar and are not the easiest things in the world to understand, here's one of the easier examples:

 $ mytest foo bar quux
   There are 3 arguments to mytest: foo bar quux
   first argument: foo
   second argument: bar
   third argument: quux
   here they are again: foo bar quux

I really can't work out how that helps me but it gave me a starting point.

So in plain language here's what I want to do, I've created a script with:

sudo nano /bin/mtupdate

The main part of the script checks for updates and installs the updates:

sudo apt-get update
sudo apt-get upgrade -y
sudo apt-get dist-upgrade -y
sudo apt-get autoremove -y

It then goes onto check what additional parameters have been passed and this is the bit that caused me heartache.

So if I run mtupdate shutdown it does the above and then this bit

# checking for shutdown parameter
if [ "$1" = "shutdown" ]; then
echo "Shutting Down in 10 seconds"
# gives you a chance to change your mind
echo "Press CTRl+C to abort"
sleep 10
echo "Shutting Down"
# shuts down
shutdown -h now
else
if

Then it became harder as I wanted to check for a reboot parameter, to get it all in I had to do the following;

# checks for reboot parameter
if [ "$1" = "reboot" ]; then
echo "Rebooting in 10 seconds"
echo "Press CTRl+C to abort"
sleep 10
echo "Rebooting"
shutdown -r now
else

# checks for shut down parameter
if [ "$1" = "shutdown" ]; then
echo "Shutting Down in 10 seconds"
echo "Press CTRl+C to abort"
sleep 10
echo "Shutting Down"
shutdown -h now

else
# no parameters
clear
echo .
echo.

echo "Updates Completed, please reboot as soon as you can"

fi fi

You have to have a fi at the end for every if in the list


The end product looks like this:

# mtupdate reboot or shutdown
echo "Running Update"
apt-get update
echo "Running Upgrade"
apt-get upgrade -y
echo "Running Dist Upgrade"
apt-get dist-upgrade -y
echo "Running Cleanup"
apt-get autoremove -y
apt-get install -fy

# checking for reboot parameter
if [ "$1" = "reboot" ]; then
echo "Rebooting in 10 seconds"
echo "Press CTRl+C to abort"
sleep 10
echo "Rebooting"
shutdown -r now
else

# checking for shutdown parameter
if [ "$1" = "shutdown" ]; then
echo "Shutting Down in 10 seconds"
echo "Press CTRl+C to abort"
sleep 10
echo "Shutting Down"
shutdown -h now

else
# no parameters entered
clear
echo .
echo .
echo "Updates Completed, please reboot as soon as you can"
fi fi

To finish it off I ran 

sudo chmod +x /bin/mtupdate 

To make it executable

My suggestion to the people that write help stuff is to use a proper example, don't use foo bar quux as this means bugger all to people like me.

My next bit of scripting is going to revolve around taking two parameters and running something based on them, such as

mtbackup source destination

Where mtbackup runs something like rsync or cp or mv

I'll come to that next time round