Convert multiple ebooks from .epub to .mobi in parallel

Kindle accepts .mobi files directly, just copy them to the root documents folder. To convert from the more common .epub, we can use the calibre CLI utility ebook-convert.

To run multiple instances in parallel, converting all .epub files in current dir, and log each process into a .log with the same name, do:

foreach x (*.epub) {
    echo -e "\n$x";
    ebook-convert $x .mobi > "$x".log 2>&1 & 
}

In the 3rd line, > redirects stdin to the file "$x".log, and 2>&1 redirects stderr to stdin to log them together. The final & runs ebook-convert as a background process, that can be monitored in htop with the printed PID, or using the jobs utility.

Connect to ssh host when it is online:

until nc -vzw 2 $host 22; do sleep 2; done && ssh $host

Very useful when rebooting hosts (VMs, IoT).

Run docker compose on git hook post-receive:

In the git server (bare repo) write the script post-receive in the folder hooks, and make it executable and owned by git:git:

#!/bin/bash
TARGET="/srv/git/flaskwiki/flaskwiki"
GIT_DIR="/srv/git/flaskwiki/flaskwiki.git"

echo "--- Deploying $GIT_DIR to Orange Pi ---"

git --work-tree=$TARGET --git-dir=$GIT_DIR checkout -f

cd $TARGET

docker compose up -d --build

echo "--- Deployment Complete ---"

Log from Flask app:

app.logger.warning(f'getting md files from {MARKDOWN_DIR}')

Any level lower that warning requires config.

Access logs from docker container:

docker logs container_name