shell scripts have a lot of brackets

here’s a cheat sheet to help you identify them all! we’ll cover the details later.

(cd ~/music; pwd)

(...) runs commands in a subshell.

VAR=$(cat file.txt)

$(COMMAND) is equal to COMMAND’S stdout

{ cd ~/music; pwd; }

(...) groups commands. runs in the same process.

x=(1 2 3)

x=(...) creates an array

x=$((2+2))

$(()) does arithmetic

if […]

/usr/bin/[ is a program that evaluates statements

<(COMMAND)

“process substitution”: an alternative to pipes

a{.png, .svg}

this expands to a.png a.svg it’s called “brace expansion”

if [[ … ]]

[[ is bash syntax. it’s more powerful than [

${var//search/replace}

see page 21 for more about ${...}!