overrideable shell environment variables macro implemented

bolt.rkt

@@ -56,8 +56,9 @@
 (define (as-user cmd)
   (if
    (user)
-     (format "sudo -u ~a sh -c \"~a\""
+     (format "sudo -u ~a ~a sh -c \"~a\""
              (user)
+             (format-vars)
              cmd)
    cmd))
 
@@ -102,4 +103,4 @@
 (define pwd (make-cmd "pwd"))
 
 (provide
-  (all-defined-out) remote compress shell-env set-vars format-vars)
+  (all-defined-out) remote compress shell-env set-vars format-vars with-shell-vars)

shell_env.rkt

@@ -1,12 +1,29 @@
 #lang racket
 
+(define default-shell-vars
+  #hash(
+        ("LANG" . "en_US.UTF-8")))
+
 (define shell-env
-  (make-parameter #hash()))
+  (make-parameter default-shell-vars))
+
+(define (remove-dups xs ys)
+  (define dups
+    (set-intersect (map car xs)
+                   (map car ys)))
+  (define new-xs
+    (filter-not
+      (compose1
+        (lambda (x) (member x dups))
+        car)
+      xs))
+    new-xs)
 
 (define (merge-hash h1 h2)
   (define h1-vs (hash->list h1))
   (define h2-vs  (hash->list h2))
-  (make-hash (append h1-vs h2-vs)))
+  (define new-h2-vs (remove-dups h2-vs h1-vs))
+  (make-hash (append new-h2-vs h1-vs)))
 
 (define (merge-hashes . hs)
   (foldl merge-hash #hash() hs))
@@ -25,8 +42,29 @@
       (lambda (k v)
         (format "~a=~a" k v)))))
 
+(define-syntax join-shell-vars
+  (syntax-rules ()
+    [(join-shell-vars (k v))
+     (merge-hash
+       (make-hash
+         (list (cons k v)))
+       (shell-env))]
+
+    [(join-shell-vars (k v) rest ...)
+     (merge-hash
+       (make-hash (list (cons k v)))
+       (join-shell-vars rest ...))]))
+
+(define-syntax with-shell-vars
+  (syntax-rules ()
+    [(with-shell-vars (vars ...) expr ...)
+      (parameterize
+        [(shell-env (join-shell-vars vars ...))]
+        (begin expr ...))]))
+
 (provide
   shell-env
   merge-hashes
   set-vars
-  format-vars)
+  format-vars
+  with-shell-vars)