redirection

• Command substitution: $(command) or `command`

• Parameter expansion: $variable, ${variable}, ${#variable}

• Arithmetic expansion: $(( expression ))

• Process substitution: <(command) or >(command)

• Redirections: >, <, >>, |, 2>

• Control flow structures: if, else, for, while, case, until

• Functions: function name() { ... }