How can I write a script to install BleachBit only if the version installed is not a certain version?

Question

I want to write a bash script to download and install BleachBit from a .deb file only if the version already installed is not 1.0. I am using Ubuntu 12.04 and Bleachbit is only version 0.9 in the official repositories and I cannot find a PPA with version 1.0 for Ubuntu Precise. How can I do this?

Answer 1

Here's a simpler version of your script, (keeping the humor intact :) ):

#!/bin/bash

## The && means that the script will run the next command only if this one
## succeeds, in other words, only if the string `version 1.0` is found.
bleachbit --version | grep -q 'version 1.0' &&
 echo "$(tput setaf 2)The elves have verified the BleachBit version.$(tput sgr0)" &&
   exit 0
## This block will only be executed if the grep above failed
wget -P ~/Downloads http://katana.oooninja.com/bleachbit/sf/bleachbit_1.0_all_ubuntu1204.deb &&
sudo dpkg -i ~/Downloads/bleachbit_1.0_all_ubuntu1204.deb &&
 echo "$(tput setaf 2)The elves have installed BleachBit 1.0.$(tput sgr0)" 

Note that I added && to the end of each command, that way, you will avoid errors if any of the commands fail since the script will exit on the first failed command.

A safer approach would be to change the first command to:

bleachbit --version | awk '/version/{if($NF>=1){exit 0}else{exit 1}}' 

This has the advantage that it will work fine for future versions, when the version number will be greater than 1. The $NF in awk means the last field and /version/ means the script will run on lines matching version. So, since the first line is:

info: starting BleachBit version 1.0

awk will test whether the last field (1.0) here is greater than or equal to one and will exit with a 0 status (success), if it is which means that the next block (&&) will be executed, and your script will stop.

You could also condense the entire thing to:

bleachbit --version | head -n 1 | awk '{if($NF>=1){exit 1}else{exit 0}}' &&
wget -P ~/Downloads http://katana.oooninja.com/bleachbit/sf/bleachbit_1.0_all_ubuntu1204.deb &&
sudo dpkg -i ~/Downloads/bleachbit_1.0_all_ubuntu1204

But that comes at the expense of the poor elves.

Answer 2

I put this short script together that seems to work for me! This also include a bit of my own brand of elvish humor. I am using this code in a larger script so I can copy and paste this conditional anywhere I need it.

#!/bin/bash

# Check BleachBit Version and install if necessary
if [ "$(bleachbit --version | grep -c 'version 1.0')" = "0" ];
    then 
        wget -P ~/Downloads http://katana.oooninja.com/bleachbit/sf/bleachbit_1.0_all_ubuntu1204.deb
        sudo dpkg -i ~/Downloads/bleachbit_1.0_all_ubuntu1204.deb
        echo "$(tput setaf 2)The elves have installed BleachBit 1.0.$(tput sgr0)"
    else
        echo "$(tput setaf 2)The elves have verified the BleachBit version.$(tput sgr0)"
fi