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diff --git a/README.md b/README.md new file mode 100644 index 0000000..b1befc1 --- /dev/null +++ b/README.md @@ -0,0 +1,6 @@ +# Bash Scripting: It's not so bad + +This is all the material for my presention on bash scripting for the DevOps +meetup (2019-05-27). The slides were presented with [mdp][1] + +[1]: https://github.com/visit1985/mdp diff --git a/slides.md b/slides.md new file mode 100644 index 0000000..9a3913f --- /dev/null +++ b/slides.md @@ -0,0 +1,318 @@ +%title: Bash Scripting: It's not so bad +%author: Cody Hiar +%date: 2019-05-27 + +-> Bash Scripting: It's not so bad <- +===================================== + +------------------------------------------------- + +# About Me + +* Graduated Computer Engineering at U of A +* SaltStack Certified +* Now working remotely @ Blendable +* Vim/Tmux Diehard, also cli in general +* Interests: Python, Automation, DevOps, Linux + +# Where I be + +* www.codyhiar.com +* www.github.com/thornycrackers + +# Past Presentations (available on GitHub) + +* Scraping with scrapy (YEGSEC) +* Python Daemons (Edmonton.py) +* Setting Django up on a VPS (Edmonton.py) +* Docker (YEGSEC) + +------------------------------------------------- + +-> Goals <- +=========== + +- What's in the Language +- Some best practices +- Resources to help + +------------------------------------------------- + +-> Why bash scripting? <- +========================= + +- Easy win with tools you already have install. +- Scripts are easy to share between different people. +- I don't like repeating myself + +^ + +-> When to bash script: <- +===================== + +^ + +- Everyday. Automate everything. Invaluable for quick throw away scenarios. + Scripting is a great way to learn how linux/unix systems in general work. + +^ + +-> When not to bash script: <- +========================= + +^ + +- Personal Take: If your script is getting past the 100ish line mark it's + probably a good time to consider moving to a different language + +------------------------------------------------- + +-> Bash has it's own language <- +================================ + +Bash has support for a bunch of the basic programming features you need such as: +Variables, Functions, If/Else, Conditionals, Loops, Arrays, Dictionaries, Case +Switch. + +------------------------------------------------- + +# Variables + +``` +NAME="John" +``` + +# Functions + +``` +get_name() { + echo "John" +} + +echo "You are $(get_name)" +``` + +# If/Else + +``` +if [[ -z "$string" ]]; then + echo "String is empty" +elif [[ -n "$string" ]]; then + echo "String is not empty" +fi +``` + +------------------------------------------------- + +# Conditionals + +``` +git commit && git push +git commit || echo "Commit failed" +``` + +# For Loop + +``` +for i in {1..5}; do + echo "Welcome $i" +done +``` + +# While Loop + +``` +while true; do + ยทยทยท +done +``` + +------------------------------------------------- + +-> The "while" poem <- +====================== + + +While true +do foo +sleep 1 +done + +``` +while true; do clear; curl https://duckduckgo.com; sleep 1; done +``` + +------------------------------------------------- + +# Array + +``` +Fruits=('Apple' 'Banana' 'Orange') + +echo ${Fruits[0]} +``` + +# Dictionaries + +``` +declare -A sounds + +sounds[dog]="bark" + +echo "${sounds[dog]}" +``` + +# Case Switch + +``` +case "$1" in + start | up) + vagrant up + ;; + + *) + echo "Usage: $0 {start|stop|ssh}" + ;; +esac +``` + +------------------------------------------------- + +-> My First Bash Script <- +========================== + +1. Run: `touch myscript.sh` +2. Add the following content + +``` +#!/usr/bin/env bash +echo "Hello World" +``` + +3. Run: `chmod +x myscript.sh` +4. Run: `./myscript.sh` + +------------------------------------------------- + +-> What can I put in a shell script <- +====================================== + +Anything you type into your terminal to run commands can be put into a bash +script. This means that Bash Scripts are essentially a free way to start +automating things that you do on a daily basis without having to install any new +tools. + +------------------------------------------------- + +-> Example: Postgres Backup <- +================================ + +``` +#!/usr/bin/env bash + +TODAY=$(date +%F) +FILENAME="database_backup-${TODAY}.sql" + +if [[ ! -f "$FILENAME" ]]; then + pg_dump -h hostname -U myuser > "$FILENAME" +fi +``` + +------------------------------------------------- + +-> Best Practice: Idempotence <- +================================ + +Plain English: Output or effect is the same if a script is ran multiple times. + +^ + +This isn't limited to Bash Scripting but is a good practice in other DevOps +tools you may be using as well. + +------------------------------------------------- + +-> Best Practice: Unofficial Strict Mode <- +=========================================== + +``` +#!/usr/bin/env bash +# +# Set options: +# e: Stop script if command fails +# u: Stop script if unset variable is referenced +# x: Debug, print commands as they are executed +# o pipefail: If any command in a pipeline fails it all fails +# +# IFS: Internal Field Separator +set -euxo pipefail +IFS=$'\\n\\t' +``` +------------------------------------------------- + +-> Best Practice: Traps <- +========================== + +``` +#!/usr/bin/env bash +function finish { + # Your cleanup code here +} +trap finish EXIT +``` + +Traps are the equivalent of wrapping your script in a giant `try/catch` +statement so that if anything does fail, the script will clean up after itself. + +------------------------------------------------- + +-> Best Practice: Linting with Shellcheck <- +============================================ + + +The goals of ShellCheck are + + To point out and clarify typical beginner's syntax issues that cause a + shell to give cryptic error messages. + + To point out and clarify typical intermediate level semantic problems that + cause a shell to behave strangely and counter-intuitively. + + To point out subtle caveats, corner cases and pitfalls that may cause an + advanced user's otherwise working script to fail under future + circumstances. + +https://github.com/koalaman/shellcheck + +------------------------------------------------- + +-> Best Practice: Automated testing with bats-core <- +===================================================== + +Bats is a TAP-compliant testing framework for Bash. It provides a simple way to +verify that the UNIX programs you write behave as expected. + +https://github.com/bats-core/bats-core + +------------------------------------------------- + +-> Resources <- +=============== + +- https://explainshell.com/ +- https://misc.flogisoft.com/bash/tip_colors_and_formatting +- https://www.bash.academy/ +- http://redsymbol.net/articles/bash-exit-traps/ +- http://redsymbol.net/articles/unofficial-bash-strict-mode/ +- https://devhints.io/bash +- https://github.com/jlevy/the-art-of-command-line +- https://google.github.io/styleguide/shell.xml +- http://www.bashoneliners.com/ +- https://www.commandlinefu.com + +- https://www.codyhiar.com/snippets/awesome-bookmarks-my-collection/ + +------------------------------------------------- + +-> Questions <- +=============== |