Add some shell utilities

shell.rkt

@@ -0,0 +1,60 @@
+#lang racket
+
+(provide with-cwd
+         with-env
+         with-temporary-dir
+         chomp
+         run
+         run/strings)
+
+(define-syntax with-cwd
+  (syntax-rules ()
+    ((_ cwd body ...)
+     (parameterize ((current-directory cwd))
+       body ...))))
+
+(define-syntax with-env
+  (syntax-rules ()
+    ((_ env body ...)
+     (parameterize ((current-environment-variables (environment-variables-copy (current-environment-variables))))
+       (for-each (lambda (v) (putenv (car v) (cdr v))) env)
+       body ...))))
+
+(define-syntax with-temporary-dir
+  (syntax-rules ()
+    ((_ body ...)     
+     (let ((tmp (chomp (run "mktemp" "-d"))))
+       (with-handlers (((lambda (v) #t)
+                        (lambda (v)
+                          (system* "/bin/rm" "-rf" tmp)
+                          (raise v))))
+         (let ((res (with-cwd tmp body ...)))
+           (system* "/bin/rm" "-rf" tmp)
+           res))))))
+
+(define (chomp s)
+  (string-trim s "\n" #:right? #t))
+
+(define (read-lines port)
+  (let read-lines ((next-line (read-line port)) (accum '()))
+    (if (eof-object? next-line)
+        (reverse accum)
+        (read-lines (read-line port) (cons next-line accum)))))
+    
+
+(define (split-lines s)
+  (string-split s #px"(\r\n|\n|\r)"))
+
+(define (run cmd . args)
+  (define-values (sp out in err) (apply subprocess #f #f #f (find-executable-path cmd) args))
+  (define stdout (port->string out))
+  (define stderr (port->string err))
+  (close-output-port in)
+  (close-input-port out)
+  (close-input-port err)
+  (subprocess-wait sp)
+  (if (not (zero? (subprocess-status sp)))
+      (raise-user-error 'run (format "error running ~a: ~a" cmd stderr))
+      stdout))
+
+(define run/strings (compose split-lines run))