Bash script which downloads the latest linux stable kernel

I made this script when I started downloading the latest stable linux kernel's source from https://www.kernel.org to compile it myself, now I have improved it a bit and decided to create a public repo for it on github (https://github.com/Tom1380/latestkernel).

This is the code (mind you this is the first time I made bash scripts):

lk (stands for latest kernel):

#!/usr/bin/env bash

cd ~

if [ ! -d "linux-stable" ]; then
    mkdir linux-stable
fi

if [ ! -f "/etc/latest_kernel" ]; then
    if  [[ $EUID > 0 ]] ; then
        echo "/etc/latest_kernel does not exist and you are not running the script as root, " \
              "please fix that either by manually running 'sudo create_etc_lk', " \
              "or rerun the script as root to automatically fix it."
        exit
    else
        touch /etc/latest_kernel
        echo "$(uname -r)" > /etc/latest_kernel
    fi
fi

wget=$(wget --output-document - --quiet https://www.kernel.org/ | grep -A 1 "latest_link")

wget=${wget##*.tar.xz\">}

wget=${wget%}

latest_acknowledged=$( 0 ]] ; then
    echo "If you wish to download the latest kernel, rerun the script as root."
    exit
fi

# Since there is only a '>', /etc/latest_kernel will be overwritten entirely.

echo "$wget" > /etc/latest_kernel

echo "Writing latest kernel available in /etc/latest_kernel."

echo "Preparing to parse link to latest kernel for wget."

wget=$(wget --output-document - --quiet https://www.kernel.org/ | grep -A 1 "latest_link")

wget=${wget##**}

echo "Done parsing."

cd ~/linux-stable

echo "Changed cwd to ~/linux-stable to download kernel source."

echo "Downloading, this may take up to 10 minutes."

wget $wget

echo "Finished downloading..."

echo "Uncompressing the kernel's source."

tar xvfJ linux-$(</etc/latest_kernel).tar.xz

echo "Done uncompressing the kernel's source."

rm linux-$(</etc/latest_kernel).tar.xz

echo "Done removing the old archive, end of the script."

create_etc_lk:

```
#!/usr/bin/env bash

if [[ $EUID > 0 ]]

Good stuff:

• Yay for putting your code on github. I see a lot of folks afraid to wait until everything is perfect to do that. But having the backup and history of git is too handy to wait like that. So I love seeing somebody doing that from day 1 of a project.

• Yay for use the double square bracket form of if and checking for common mistakes.

• Yay for using env. As you can see from my github I'm not so great at this one, but it is a good idea.

Suggestions:

-
Move common code into a library. Your EUID check is the most obvious culprit. To create a shell library you should create a file of functions and then source it into each of your commands. So to translate your check into a function is easy:

function validate_root {
    if [[ $EUID > 0 ]] ; then
            echo "You need root privileges for this script."
            exit
    fi
}

Then use the library later like so:

source lib.sh

validate_root # be root or exit

-
Move common data into the library. The most common item is /etc/latest-kernel... what if you want to move it somewhere else? If it is in a variable in one place it will be a lot easier to do. There's no reason not to throw those into the common shell library file too.

• It looks like you made a cut and paste error on purgelatestkernel but since I can check out the github version I can see what you meant there. Generally you're not supposed to edit code during code review put I think you'd be ok to fix that part up since you're not altering the code you meant to review.

-
Avoid duplicate code by looping in the install:

for file in lk create_etc_lk purgelatestkernel
do
        echo copying $file to /usr/bin
        cp $file /usr/bin
done

This also makes it easy to add other things like a validation of permissions or check for return values without insane amounts of error-prone cut and paste.

• Instead of having the option for a prompt be something that requires a source code alteration why not make it conditional based on a variable that possibly could be altered with a command line option?

StackExchange Code Review Q#163318, answer score: 2