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(define-module (hnh util env)
:export (let-env with-working-directory))
(define-syntax let-env
(syntax-rules ()
[(_ ((name value) ...)
body ...)
(let ((env-pairs #f))
(dynamic-wind
(lambda ()
(set! env-pairs
(map (lambda (n new-value)
(list n new-value (getenv n)))
(list (symbol->string (quote name)) ...)
(list value ...)))
(for-each (lambda (pair) (setenv (car pair) (cadr pair)))
env-pairs))
(lambda () body ...)
(lambda ()
(for-each (lambda (pair) (setenv (car pair) (caddr pair)))
env-pairs))))]))
;; TODO this probably isn't threadsafe... pthreads(7) notes
;; that chdir is shared between all threads.
(define-syntax-rule (with-working-directory directory thunk)
(let ((old-cwd #f))
(dynamic-wind
(lambda ()
(set! old-cwd (getcwd))
(chdir directory))
thunk
(lambda () (chdir old-cwd)))))
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