ambrevar/shell: Extend `env'.

.local/share/common-lisp/source/ambrevar/shell.lisp

@@ -15,11 +15,20 @@
   (local-time:format-rfc1123-timestring nil (local-time:now)))
 
 (export-always 'env)
-(defun env ()
-  "Return the environment variables as an alist."
-  (mapcar (lambda (line)
-            (str:split "=" line :limit 2))
-          (str:split (string #\newline) (cmd:$cmd "env"))))
+(defun env (&optional key)
+  "Return the environment variables as a proper alist.
+With KEY, return the corresponding environment variable value, and the whole
+list as a second value."
+  (let ((result
+          (mapcar (lambda (line)
+                    (let ((key-value (str:split "=" line :limit 2)))
+                      (cons (first key-value)
+                            (str:split (uiop:inter-directory-separator)
+                                       (second key-value)))))
+                  (str:split (string #\newline) (cmd:$cmd "env")))))
+    (if key
+        (alex:assoc-value result key :test #'string=)
+        result)))
 
 (export-always 'file->string)
 (defun file->string (path)