diff --git a/guix/scripts/build.scm b/guix/scripts/build.scm
index 35b10a0..8937d76 100644
--- a/guix/scripts/build.scm
+++ b/guix/scripts/build.scm
@@ -37,6 +37,7 @@
#:export (%standard-build-options
set-build-options-from-command-line
show-build-options-help
+ specification->package
guix-build))
diff --git a/guix/scripts/prefetch.scm b/guix/scripts/prefetch.scm
new file mode 100644
index 0000000..dbcef0f
--- /dev/null
+++ b/guix/scripts/prefetch.scm
@@ -0,0 +1,141 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 Nikita Karetnikov
+;;; Copyright © 2014 Ludovic Courtès
+;;;
+;;; 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 .
+
+(define-module (guix scripts prefetch)
+ #:use-module (guix derivations)
+ #:use-module (guix packages)
+ #:use-module (guix store)
+ #:use-module (guix ui)
+ #:use-module (guix utils)
+ #:use-module (guix scripts build)
+ #:use-module (ice-9 match)
+ #:use-module (srfi srfi-1)
+ #:use-module (srfi srfi-11)
+ #:use-module (srfi srfi-26)
+ #:use-module (srfi srfi-37)
+ #:export (guix-prefetch))
+
+;;; Commentary:
+;;;
+;;; This program is used to download and add to the store all inputs that are
+;;; needed to build the specified packages.
+;;;
+;;; Code.
+
+(define (derivation-input->derivation input)
+ (call-with-input-file (derivation-input-path input)
+ read-derivation))
+
+(define* (derivations-to-prefetch store package #:key (use-substitutes? #t))
+ "Return the list of fixed-output derivations for PACKAGE."
+ (filter fixed-output-derivation?
+ (map derivation-input->derivation
+ (derivation-prerequisites-to-build
+ store
+ (package-derivation store package)
+ #:use-substitutes? use-substitutes?))))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+ '((substitutes? . #t)))
+
+(define (show-help)
+ (display (_ "Usage: guix prefetch [OPTION]... PACKAGES...
+Download and add to the store all inputs that are needed to build
+PACKAGES.\n"))
+ (display (_ "
+ -n, --dry-run do not build the derivations"))
+ (display (_ "
+ --no-substitutes build instead of resorting to pre-built substitutes"))
+ (display (_ "
+ -h, --help display this help and exit"))
+ (display (_ "
+ -V, --version display version information and exit"))
+ (newline)
+ (show-bug-report-information))
+
+(define %options
+ ;; Specification of the command-line options.
+ (list (option '("no-substitutes") #f #f
+ (lambda (opt name arg result . rest)
+ (apply values
+ (alist-cons 'substitutes? #f
+ (alist-delete 'substitutes? result))
+ rest)))
+ (option '(#\n "dry-run") #f #f
+ (lambda (opt name arg result)
+ (alist-cons 'dry-run? #t result)))
+
+ (option '(#\h "help") #f #f
+ (lambda args
+ (show-help)
+ (exit 0)))
+ (option '(#\V "version") #f #f
+ (lambda args
+ (show-version-and-exit "guix prefetch")))))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-prefetch . args)
+ (define (parse-options)
+ ;; Return the alist of option values.
+ (args-fold* args %options
+ (lambda (opt name arg result)
+ (leave (_ "~A: unrecognized option~%") name))
+ (lambda (arg result)
+ (alist-cons 'argument arg result))
+ %default-options))
+
+ (let* ((opts (parse-options))
+ (dry-run? (assoc-ref opts 'dry-run?))
+ (substitutes? (assoc-ref opts 'substitutes?))
+ (store (open-connection))
+ (drvs
+ (append-map (lambda (package)
+ (derivations-to-prefetch
+ store
+ package
+ #:use-substitutes? substitutes?))
+
+ (delete-duplicates
+ (filter-map (match-lambda
+ (('argument . value)
+ (identity ; discard the second value
+ ;; Check that all VALUEs in the list are
+ ;; valid packages before calling
+ ;; 'derivations-to-prefetch'. If VALUE
+ ;; is not a valid package,
+ ;; 'specification->package' will raise
+ ;; an error.
+ (specification->package value)))
+ (_ #f))
+ (reverse opts))))))
+ (show-what-to-build store
+ drvs
+ #:dry-run? dry-run?
+ #:use-substitutes? substitutes?)
+ (unless dry-run?
+ (build-derivations store drvs))))