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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2018 Mathieu Othacehe <m.othacehe@gmail.com>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu installer utils)
+  #:use-module (guix utils)
+  #:use-module (guix build utils)
+  #:use-module (ice-9 rdelim)
+  #:use-module (ice-9 regex)
+  #:use-module (ice-9 textual-ports)
+  #:export (read-lines
+            read-all
+            nearest-exact-integer
+            read-percentage
+            run-shell-command))
+
+(define* (read-lines #:optional (port (current-input-port)))
+  "Read lines from PORT and return them as a list."
+  (let loop ((line (read-line port))
+             (lines '()))
+    (if (eof-object? line)
+        (reverse lines)
+        (loop (read-line port)
+              (cons line lines)))))
+
+(define (read-all file)
+  "Return the content of the given FILE as a string."
+  (call-with-input-file file
+    get-string-all))
+
+(define (nearest-exact-integer x)
+  "Given a real number X, return the nearest exact integer, with ties going to
+the nearest exact even integer."
+  (inexact->exact (round x)))
+
+(define (read-percentage percentage)
+  "Read PERCENTAGE string and return the corresponding percentage as a
+number. If no percentage is found, return #f"
+  (let ((result (string-match "^([0-9]+)%$" percentage)))
+    (and result
+         (string->number (match:substring result 1)))))
+
+(define (run-shell-command command)
+  (call-with-temporary-output-file
+   (lambda (file port)
+     (format port "~a~%" command)
+     ;; (format port "exit~%")
+     (close port)
+     (invoke "bash" "--init-file" file))))