====================================
While statements
====================================

while something happens; do
  echo a
  echo b
done

---

(program
  (while_statement
    (command (command_name) (argument))
    (do_group
      (command (command_name) (argument))
      (command (command_name) (argument)))))

====================================
If statements
====================================

if cat some_file | grep -v ok; then
  echo one
elif cat other_file | grep -v ok; then
  echo two
else
  exit
fi

---

(program
  (if_statement
    (pipeline
      (command (command_name) (argument))
      (command (command_name) (argument) (argument)))
    (command (command_name) (argument))
    (elif_clause
      (pipeline
        (command (command_name) (argument))
        (command (command_name) (argument) (argument)))
      (command (command_name) (argument)))
    (else_clause
      (command (command_name)))))

====================================
If statements with conditional expressions
====================================

if [ "$(uname)" == 'Darwin' ]; then
  echo one
fi

---

(program
  (if_statement
    (bracket_command
      (quoted_argument (command_substitution (command (command_name))))
      (argument)
      (single_quoted_argument))
    (command (command_name) (argument))))

====================================
Case statements
====================================

case "opt" in
  a)
    echo a
    ;;

  b)
    echo b
    ;;
esac

---

(program
  (case_statement (quoted_argument)
    (case_item (argument)
      (command (command_name) (argument)))
    (case_item (argument)
      (command (command_name) (argument)))))

===============================
Subshells
===============================

(
  ./start-server --port=80
) &

---

(program
  (subshell (command (command_name) (argument))))