Linux, bash, Docker snippets

#!/usr/bin/env bash
set -o errexit  # Exit immediately when a command fails.
set -o nounset  # Treat unset variables and parameters as an error when performing parameter expansion.
set -o pipefail # the return value of a pipeline is the value of the last (rightmost) command to exit with a non-zero status, or zero if all commands in the pipeline exit successfully

# Set VAR to DEFAULT if no command line argument exists
VAR="${1:-"DEFAULT"}"

# Functions and local variables
hello_world(){
  local name="$1"
  echo "Hello world: ${name}"
}

# if then
if [[ "$NAME" = "Dirk" || "$USER_NAME" = "Jose" ]]; then
  ...
fi

## Directory exists
[[ -d ${file} ]]

## File exists
[[ -e ${file} ]]

find . -empty -type d -delete

grep -EiEio '\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b' <filename>

# Build an image with name and tag djg:1.0
docker build . -t djg:1.0
# Start container detached with port 8000 forwarded to port 5000
docker run -p 8080:5000 -d djg:1.0

# List running containers
docker container ls

# Run more processes in a container
docker exec -ti my_container sh -c "echo a && echo b"
# Stop container
docker stop my_container

# Run bash container interactively and connect to terminal
docker run -it bash

# Rerun a container
docker start -ai my_container

# Inspect my_container
docker inspect my_container
# Inspect volume_id
docker volume inspect volume_id

# List docker images
docker images

# Show information about running containers
docker ps -a -s

# Clean up everything and don't ask
docker system prune -af --volumes

# Remove all stopped containers
docker rm $(docker ps --filter status=exited -q)

# Run x86-64 alpine image
docker run -it --rm --platform linux/amd64 alpine

# Run Python 3.13 image and mount cwd as /code into the container
docker run -it --rm -v .:/code python:3.13 /bin/bash

# list indexes
GET /_cat/indices?v

# list disk allocation
GET /_cat/allocation?v

# delete an index
DELETE my-old-index

# Make all jpeg files in a directrory smaller
mogrify -strip -quality 75% *.jpg

NUMBER_OF_LINES=25
while mapfile -t -n $NUMBER_OF_LINES ary && ((${#ary[@]})) ; do
  echo "${ary[@]}"
  # ... do something useful here
done < input_file

# Rule that is always true
  rules:
    - when: always