== Title

Description
[[toc:]]
=== {{call-with-environment-variables}}
<procedure>(call-with-environment-variables variables thunk) → unspecified</procedure>
Sets up environment variable via dynamic-wind which are taken down after thunk.
; variables : An alist of the form '(("var" . "value") ...)
; thunk : The thunk to execute with a modified environment
<enscript highlight="scheme">(define (call-with-environment-variables variables thunk)
  (let ((pre-existing-variables
          (map (lambda (var-value)
                 (let ((var (car var-value)))
                   (cons var (get-environment-variable var))))
               variables)))
    (dynamic-wind
      (lambda () (void))
      (lambda ()
        (use posix)
        (for-each
          (lambda (var-value) (setenv (car var-value) (cdr var-value)))
          variables)
        (thunk))
      (lambda ()
        (for-each
          (lambda (var-value)
            (let ((var (car var-value)) (value (cdr var-value)))
              (if value (setenv var value) (unsetenv var))))
          pre-existing-variables)))))
</enscript>
=== About this egg

==== Author

[[/users/anonymous|Anonymous]]
==== Colophon

Documented by [[/egg/cock|cock]].