Bash Cheatsheet

Last updated January 14, 2022 by Jacob Paris

Run a then b

a; b

Run a, and if it succeeds run b

a && b

Run a if a directory exists

[[ -d node_modules ]] && a

Run npm i if a node_modules doesn't exist

[[ ! -d node_modules ]] && npm i

Run npm start in a directory src

(cd src; npm start)

Output text

echo "Text"

Output text to a file

echo "Text" > file.txt

Append text to a file

echo "Text" >> file.txt

Run a function

hello () {
echo "Hello!"
}
hello

Run a function with arguments

hello () {
echo "Hello, $1"
}
hello "world"

Print Variable VAR not set if VAR doesn't exist

: ${VAR:?"Variable VAR not set"}

Exit if docker is not installed

if [ ! "$(command -v docker)" ]; then
echo "🐳 Docker daemon not installed"
exit 1
fi

Suppress error output

docker run server 2>/dev/null