=============================
Literal words
=============================

echo a
echo a b

---

(program
  (command (command_name) (word))
  (command (command_name) (word) (word)))

=============================
Simple variable expansions
=============================

echo $abc

---

(program
  (command (command_name) (simple_expansion (variable_name))))

=============================
Variable expansions
=============================

echo ${abc}
echo ${abc:-def}

---

(program
  (command (command_name) (expansion (variable_name)))
  (command (command_name) (expansion (variable_name) (word))))

===================================
Other variable expansion operators
===================================

cat ${BAR} ${ABC=def} ${GHI:?jkl}

---

(program
  (command
    (command_name)
    (expansion (variable_name))
    (expansion (variable_name) (word))
    (expansion (variable_name) (word))))

=============================
Command substitutions
=============================

echo `echo hi`
echo $(echo $(echo hi))

---

(program
  (command
    (command_name)
    (command_substitution (command (command_name) (word))))
  (command
    (command_name)
    (command_substitution (command
      (command_name)
      (command_substitution (command
        (command_name)
        (word)))))))

=============================
Process substitutions
=============================

wc -c <(echo abc && echo def)
echo abc > >(wc -c)

---

(program
  (command
    (command_name)
    (word)
    (process_substitution (list
      (command (command_name) (word))
      (command (command_name) (word)))))
  (command
    (command_name)
    (word)
    (file_redirect (process_substitution
      (command (command_name) (word))))))

=============================
Single quoted strings
=============================

echo 'a b' 'c d'

---

(program
  (command (command_name) (raw_string) (raw_string)))

=============================
Double quoted strings
=============================

echo "a" "b"
echo "a ${b} c" "d $e"

---

(program
  (command (command_name)
    (string)
    (string))
  (command (command_name)
    (string (expansion (variable_name)))
    (string (simple_expansion (variable_name)))))