Execute shell script: ./script.sh, bash script.sh, source script.sh

Read user input: read

Echo text to screen: echo

Arithmetic operations: let, expr

Conditional statements: if, case

Loops: for, while

Array operations: declare, read -a

Check file/directory existence: -e, -d, -f

Check file permissions: -r, -w, -x

Check file type: -b, -c, -L, -S