installation - How do Linux binary installers (.bin, .sh) work?

Question

Some software (for ex. the NetBeans IDE) ship the Linux installers in .sh files. Curious about how exactly they 'package' a whole IDE into a 'shell script', I opened the file in an editor. I saw some plain text shell scripting code and then some random gibberish, which I reckon is 'binary' or non-plain text.

I am wondering how they mix plain shell scripts and then probably call the 'non-readable' stuff, which would be the binaries.

Any insight on this?

Answer 1

Basically, it's a shell script prepended to a compressed archive of some sort, such as a tar archive. You use the tail or sed command on yourself (the $0 variable in Bourne shell) to strip off the shell script at the front and pass the rest to your unarchiver.

For example, create the following script as self-extracting:

#!/bin/sh -e
sed -e '1,/^exit$/d' "$0" | tar xzf - && ./project/Setup
exit

The sed command above deletes all lines from the first line of the file to the first one that starts with "exit", and then passes the rest on through. If what starts immediately after the "exit" line is a tar file, the tar command will extract it. If that's successful, the ./project/Setup file (presumably extracted from the tarball) will be executed.

Then:

mkdir project
echo "#!/bin/sh" > project/Setup
echo "echo This is the setup script!" >> project/Setup
chmod +x project/Setup
tar czf - project >> self-extracting

Now, if you get rid of your old project directory, you can run self-extracting and it will extract that tar file and run the setup script.