![Cache
Takeaways
# Arithmetic
local sum=$(($a + 5))
if (($age > $max_age)); then
# Conditionals
if [[ -f $file ]]; then
// elif/else/fi
# -d (dir)
# Pipes
trace=$(cat $file | grep Akamai)](https://image.slidesharecdn.com/bashfordevops-221110114543-dfb578d1/85/Bash-the-1-skill-for-Devops-Engineers-15-320.jpg)
![tag.sh
Takeaways
# Print line
before executing
[[ "$TRACE" ]] && set -x
# Trim all 'v' from left
new_version=${1##v}
# '%' from right
# Echo to stderr
echoerr() { echo "$@" 1>&2; }
# Command with if
if ! grep $version ./r.md; then
# AWK
awk "/^#.*$new_version/{flag=1;next}/^#/{flag=0}flag" $file](https://image.slidesharecdn.com/bashfordevops-221110114543-dfb578d1/85/Bash-the-1-skill-for-Devops-Engineers-19-320.jpg)
![tag.sh
Takeaways
# Git multiple -m
git commit -am "Release $new_version" -m "$description"
# Git return values
if ! git diff --quiet HEAD; then
# sed
sed -i.bak -E "s/[0-9]+.[0-9]+.[0-9]+/$new_version/g" $file](https://image.slidesharecdn.com/bashfordevops-221110114543-dfb578d1/85/Bash-the-1-skill-for-Devops-Engineers-21-320.jpg)
Bash: the #1 skill for Devops Engineers
- 1. Bash: The #1 Skill for DevOps Engineers anders.janmyr@ingka.ikea.com
- 2. Bash: The #1 Skill for DevOps Engineers
- 4. Bash: Ugly... Propositions It's a script. It's not a server. Make it work! Clean it up! Move on! Byte-sized :) Google Copy-Paste Learn! Make it work locally! Then on CI server.
- 5. BAD! Don't code in YAML! GOOD! Code in script.
- 6. first.sh
- 8. first.sh Takeaways # First command that reads STDIN will wait for input. # Every script has STDIN, STDOUT, STDERR Exit status # Exit status can be used in conditionals # STDOUT can be captured
- 9. args.sh
- 10. args.sh
- 11. simple.sh Takeaways set -o errexit # Exits if a command fails "$1", "$2",... "$@" # Always quote args # Every line executes a command '$1' # No var expansion
- 12. Here docs <<-
- 13. Here docs Takeaways "$a_var", "$(ls)" # variable expansion # cmd execution $(cat <<-whatever "Quote": "without escaping" set -o pipefail # Exits if a command fails in pipe # Great for generating JSON
- 14. Caching
- 15. Cache Takeaways # Arithmetic local sum=$(($a + 5)) if (($age > $max_age)); then # Conditionals if [[ -f $file ]]; then // elif/else/fi # -d (dir) # Pipes trace=$(cat $file | grep Akamai)
- 16. Functions
- 17. Functions Takeaways # Call ret=my_function abc out=$(my_function abc) # Vars "${file?is required}" "${1?file is required}" "${1:-default}" my_function() { local v="$1" echo "out $v" }
- 18. tag.sh
- 19. tag.sh Takeaways # Print line before executing [[ "$TRACE" ]] && set -x # Trim all 'v' from left new_version=${1##v} # '%' from right # Echo to stderr echoerr() { echo "$@" 1>&2; } # Command with if if ! grep $version ./r.md; then # AWK awk "/^#.*$new_version/{flag=1;next}/^#/{flag=0}flag" $file
- 20. tag.sh cont.
- 21. tag.sh Takeaways # Git multiple -m git commit -am "Release $new_version" -m "$description" # Git return values if ! git diff --quiet HEAD; then # sed sed -i.bak -E "s/[0-9]+.[0-9]+.[0-9]+/$new_version/g" $file
- 22. Trap Signals
- 23. Trap Signals cleanup() { rm -rf $tmp_template } trap cleanup EXIT # Signals EXIT - Program Exit SIGINT - Ctrl-C from the keyboard SIGQUIT - Ctrl- from the keyboard
- 24. Useful Commands
- 27. When should I not use Bash? Large Programs > 100 Lines Complex structures Maps/Dicts/Structs