Add directory stack to cd

src/common/closh/zero/builtin.cljc

@@ -33,12 +33,46 @@
           (fn [[k v]] (process/setenv k v))
           (partition 2 args))))
 
+(def ^:private dir-stack (atom (list (getenv "PWD"))))
+
+;;; Push and entry on the directory stack
+(defn- push-dir
+  [dir]
+  (swap! dir-stack (comp distinct conj) dir))
+
+(defn dh
+  "Show the current directory stack"
+  []
+  (println
+   (clojure.string/join "\n" (map-indexed #(str %1 " " %2) @dir-stack))))
+
 (defn cd
-  "Changes current working directory to a path of a first given argument."
+  "Changes current working directory to a path of a first given argument.
+  If the first arg is like -<N> it will use the Nth entry on the directory
+  stack. A '-' changes directory to the previous directory."
   [& args]
   ;; flatten is used because we can get arguments from expand which are collections
-  (let [dir (or (first args)
-                (getenv "HOME"))]
-    (process/chdir dir)
-    (setenv "PWD" (process/cwd))
-    env/success))
+  (let [arg (first args)]
+    (if-let [dir (cond (nil? arg)       ;go home if no arg
+                       (getenv "HOME")
+
+                       ;; a lone '-' will change to the last directory
+                       (= arg "-")
+                       (nth @dir-stack 1)
+
+                       ;; a -<N> shows up in the arg list as a negative number
+                       (and (integer? arg)
+                            (< arg 1))
+                       (nth @dir-stack (- arg))
+
+                       ;; just use the arg
+                       :else arg)]
+      (do (process/chdir dir)
+          (let [cwd (process/cwd)]
+            ;; save the directory on the directory stack
+            (push-dir cwd)
+            (setenv "PWD" cwd))
+          env/success)
+      ;; if we don't have a directory then fail (shouldn't really get
+      ;; here).
+      env/failure)))

src/common/closh/zero/compiler.cljc

@@ -5,7 +5,7 @@
 
 (def ^:no-doc builtins
   "Set of symbols of builtin functions"
-  #{'cd 'exit 'quit 'getenv 'setenv})
+  #{'cd 'exit 'quit 'getenv 'setenv 'dh})
 
 (def ^:no-doc pipes
   "Maps shorthand symbols of pipe functions to full name"

src/common/closh/zero/env.cljc

@@ -13,7 +13,7 @@
             '[closh.zero.compiler]
             '[closh.zero.parser]
             '[closh.zero.core :refer [shx expand]]
-            '[closh.zero.builtin :refer [cd exit quit getenv setenv]]
+            '[closh.zero.builtin :refer [cd exit quit getenv setenv dh]]
             '[closh.zero.platform.process]
             '[closh.zero.pipeline]
             '[clojure.string :as str]