Bash script to update Debian type systems, a couple of questions

k3lt01 · 11-15-2011, 01:02 AM

Hi everyone

I have written a script to update Debian type systems and it works until the end where it just stops. I also have it installing Debdelta so it can use debdelta to minimise download times.

My questions are, can I get the script to work out if it needs to install Debdelta and then continue on if it doesn't?
Also can anyone see why it just stops at the end without actually upgrading?

Code:

#!/bin/bash
# A script to update package lists, creates debs from available deltas
# and upgrade the system without adding or removing anything.
echo "This script relies on debdelta being install on your system for it to
  work effectively"
read -p "Do you wish to install debdelta? (Y/n)"
	if [ "$REPLY" = "n" -o "$REPLY" = "N" ]; then
		echo "closing now"
		sleep 5
		exit 1
	fi
	if [ "$REPLY" = "y" -o "$REPLY" = "Y" ]; then
		echo
		echo "This script requires super-user access to continue."
		echo 'Checking for super-user access...'
		echo
		# Temporarily set sudo timeout to 360 mins
		echo "Defaults passwd_timeout=360" | sudo tee -a /etc/sudoers > /dev/null
		echo -en $WHITE "Access Granted." $GRAY

		echo "installing debdelta now"
		sudo aptitude update
		sudo aptitude install debdelta
		read -p "debdelta installed. Do you wish to continue? (Y/n)"
			if [ "$REPLY" = "n" -o "$REPLY" = "N" ]; then
			echo "closing now"
			sleep 5
			exit 1
		fi
		if [ "$REPLY" = "y" -o "$REPLY" = "Y" ]; then
			echo "starting update/upgrade now"
			sudo aptitude update
			sudo debdelta-upgrade
			sudo aptitude safe-upgrade
		fi
	fi
fi

evo2 · 11-15-2011, 01:10 AM

Hi,

you can use something like 'dpkg -l <package>' to find out if a given package is installed.
If you indent the script properly I think you'll see you've got an extra fi.

Cheers,

Evo2.

evo2 · 11-15-2011, 01:14 AM

Opps, sorry, not 'dpkg -i', 'dpkg -s'.

Eg.

Code:

dpkg -s debdelta > /dev/null 2>&1
if [ "$?" != "0" ] ; then
  echo "Please install debdelta"
  exit 1
fi

Cheers,

Evo2.

k3lt01 · 11-15-2011, 01:33 AM

Hi Evo
Thanks for your reply. I see how that would work on its own, yes I tried it after reading the man page (should have read that before lol) but I can't see how to add it to the script. Should I use grep or something similar?

evo2 · 11-15-2011, 01:39 AM

Hi,

well, first test if it is installed then if it is not you can ask the user if they want to install it, or otherwise exit.

Something like:

Code:

dpkg -s debdelta > /dev/null 2>&1
if [ "$?" != "0" ] ; then
  echo "It seems debdelta is not installed.
  read -p "This script needs debdelta. Can I install it? y/n >" 
  if [ "$REPLY" != "y" ] ; then
    exit 1
  fi
  sudo apt-get install debdelta
fi

Cheers,

Evo2.

grail · 11-15-2011, 01:44 AM

Quote:

I see how that would work on its own

I am not sure why you think it would work any differently in your script?

You can also make it a little simpler (as your using bash):

Code:

if ! dpkg -s debdelta > /dev/null 2>&1
then
  echo "Please install debdelta"
  exit 1
fi

k3lt01 · 11-15-2011, 01:47 AM

Quote:

Originally Posted by evo2

Hi,

well, first test if it is installed then if it is not you can ask the user if they want to install it, or otherwise exit.

[code]
dpkg -s debdelta > /dev/null 2>&1
if [ "$?" != "0" ] ; then
echo "It seems debdelta is not installed.
echo "This script needs debdelta. Can I install it?"

exit 1
fi

Shouldn't something be infront of dpkg so the script can use it? like if, read, fi, echo etc, that is what I am confused with.

k3lt01 · 11-15-2011, 01:54 AM

Quote:

Originally Posted by grail

I am not sure why you think it would work any differently in your script?

Hi grail. I test things on their own before I try them with other things, it is how I work through things. It is the way I diagnose things that I don't know how to do. I'm basically sitting here teaching myself scripting.

Quote:

Originally Posted by grail

You can also make it a little simpler (as your using bash):

Code:

if ! dpkg -s debdelta > /dev/null 2>&1
then
  echo "Please install debdelta"
  exit 1
fi

Doesn't seem to want to work in the script

trappa01 · 11-15-2011, 02:15 AM

Quote:

Shouldn't something be infront of dpkg so the script can use it? like if, read, fi, echo etc, that is what I am confused with.

No. It just runs the command and bins the output. The next line check the return code for the command. If the package is installed $?=0 . Otherwise $?=1.

The later version.

Code:

if ! dpkg -s debdelta > /dev/null 2>&1
then
  echo "Please install debdelta"
  exit 1
fi

does the same thing but compares the result of the command at execution.

k3lt01 · 11-15-2011, 02:42 AM

Ok the adddition is now working, sort of, in the script. One thing is wrong, everytime I run it it still wants to install debdelta which is already installed.

k3lt01 · 11-15-2011, 03:12 AM

I think I know what's going wrong with the debdelta installation, I haven't given any options in the script so it is still going to install debdelta because the script says to. There isn't any conditional to say hey if it isn't installed install it but if it is installed move to the next section.

I'll have to do some more reading, I don't know at the moment how to use the /dev/null to say move to the next section cause you already have debdelta or if I need to modify the next section.

EDIT: Also what's the proper format for indentation? I have been using the tab key.

grail · 11-15-2011, 03:50 AM

Indentation is a personal thing and tab is fine if you like the look of it

As for how to utilise the code simply place install part inside if.

trappa01 · 11-15-2011, 03:52 AM

Don't worry too much about /dev/null for your script. It is only a "bin" device that acts like a black hole. If you run a command but don't want the output clogging up your screen, you send the output to /dev/null. This does not change the result of the command, just the output. The example also adds 2>$1 which says to also send stderr to /dev/null.

k3lt01 · 11-15-2011, 04:21 AM

Thanks guys, I have the debdelta part working perfectly now but the upgrade still isn't working as it should. There is a error at the end but it flashes by and then the terminal closes. Is there a way to create a readable log file from what is on the terminal screen?

My current file looks like this

Code:

#!/bin/bash
# A script to update package lists, creates debs from available deltas
# and upgrades the system without adding anything that is not required or
# removing something that is required.
# Created by me so I could teach myself scripting
# with help from trappa01, grail, and evo2 from LinuxQuestions.
if ! dpkg-query -l debdelta = i > /dev/null 2>&1
then 
	echo "This script requires super-user access to continue."
	echo 'Checking for super-user access...'
	echo
	# Temporarily set sudo timeout to 360 mins
	echo "Defaults passwd_timeout=360" | sudo tee -a /etc/sudoers > /dev/null
	echo -en $WHITE "Access Granted." $GRAY
	echo "starting update/upgrade now"
	sudo aptitude update
	sudo debdelta-upgrade
	sudo aptitude safe-upgrade
	fi
fi
else
	echo "It seems debdelta is not installed."
	read -p echo "This script relies on debdelta being installed /non your system for it to work effectively"
	read -p "Do you wish to install debdelta? (Y/n)"
	if [ "$REPLY" = "n" -o "$REPLY" = "N" ]; then
		echo "closing now"
		sleep 5
		exit 1
	fi
	if [ "$REPLY" = "y" -o "$REPLY" = "Y" ]; then
		echo
		echo "installing debdelta now"
		sudo aptitude update
		sudo aptitude install debdelta
		read -p "debdelta installed. Do you wish to continue? (Y/n)"
			if [ "$REPLY" = "n" -o "$REPLY" = "N" ]; then
			echo "closing now"
			sleep 5
			exit 1
		fi
		if [ "$REPLY" = "y" -o "$REPLY" = "Y" ]; then
			echo "starting update/upgrade now"
			sudo aptitude update
			sudo debdelta-upgrade
			sudo aptitude safe-upgrade
		fi
	fi
fi

grail · 11-15-2011, 04:30 AM

Well, evo pointed out in his first post that you have to look at how many times you open / close your if statements.

Also I cannot understand how you new if statement works?

Code:

if ! dpkg-query -l debdelta = i > /dev/null 2>&1

Remembering that a script just helps you from typing a lot of stuff at the command line, what do you get when you run the following on the command line:

Code:

dpkg-query -l debdelta = i

Because I get errors, which of course are hidden by outputting to /dev/null as pointed out by trappa01