How to extract first file from cbz files in one batch?

Question

I have a collection of comic books that I store on my computer, mostly in .cbz format (which is just a ZIP archive, but with a fancy name). Recently, I decided to make a collage of the covers of a specific comic series, for which I'd need the first file in the comic book archive.

Here's the breakdown of the problem:

• 75 .cbz files in a single folder;
• Each file has a name like <series name> #<issue number>, where issue numbers go from 1 to 75 (one problem: it's not like 01, 02, 03, etc, so there may be a confusion with sorting there);
  • Each file inside each archive is named like <issue name> <3-digit issue number with preceding zeros>
• Archives can be renamed to .zip if necessary, but I know 7Zip (and some other archivers, but not unrar) handles CBZ well enough;

What I need:

• The first file from each of the 75 archives. The files already have distinctive names, so there's no need to rename them at the output.

What I have:

• Ubuntu 16.04
• 7Zip
• Internet connection

How do I make this happen? What command will extract the first file from every archive in a folder to the same folder?

Answer 1

If you don't need to rename output files then I suggest something like this:

#!/bin/bash

for file in *.cbz
do
 cover="`zipinfo -2 "$file" | awk 'NR==2 {exit} 1'`"
 unzip -j "$file" "$cover"
done;

Save it in a file like script.sh and put it into the same directory as your comics are. Then give it execute permission:

chmod +x script.sh

And run it:

./script.sh

---

How does it work?

We can get a list of all files within a zip archive using zipinfo:

zipinfo -2 mycomic.cbz

it outputs something similar to:

First file within the archive.jpg
Second file within the archive.jpg
...

Then using awk 'NR==1 { print }' we can return the first file name which is: First file within the archive.jpg.

Now to extract this file I can use a unzip like:

unzip -j mycomic.cbz "First file within the archive.jpg"