01/03: services: Add 'session-environment-service'.

[???]

iyzsong pushed a commit to branch master
in repository guix.

commit e10964efd26fdbc3f8b2b5c3a0d359916df1b914
Author: 宋文武 <address@hidden>
Date:   Wed Dec 2 19:59:29 2015 +0800

    services: Add 'session-environment-service'.
    
    * gnu/services/base.scm (session-environment-service): New procedure.
    (session-environment-service-type): New variable.
    (environment-variables->environment-file): New procedure.
---
 gnu/services/base.scm |   36 ++++++++++++++++++++++++++++++++++++
 1 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index c242c7d..a86e8e0 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -2,6 +2,7 @@
 ;;; Copyright © 2013, 2014, 2015 Ludovic Courtès <address@hidden>
 ;;; Copyright © 2015 Alex Kost <address@hidden>
 ;;; Copyright © 2015 Mark H Weaver <address@hidden>
+;;; Copyright © 2015 Sou Bunnbu <address@hidden>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -48,6 +49,8 @@
             device-mapping-service
             swap-service
             user-processes-service
+            session-environment-service
+            session-environment-service-type
             host-name-service
             console-keymap-service
             console-font-service
@@ -368,6 +371,39 @@ stopped before 'kill' is called."
 
 
 ;;;
+;;; System-wide environment variables.
+;;;
+
+(define (environment-variables->environment-file vars)
+  "Return a file for pam_env(8) that contains environment variables VARS."
+  (apply mixed-text-file "environment"
+         (append-map (match-lambda
+                       ((key . value)
+                        (list key "=" value "\n")))
+                     vars)))
+
+(define session-environment-service-type
+  (service-type
+   (name 'session-environment)
+   (extensions
+    (list (service-extension
+           etc-service-type
+           (lambda (vars)
+             (list `("environment"
+                     ,(environment-variables->environment-file vars)))))))
+   (compose concatenate)
+   (extend append)))
+
+(define (session-environment-service vars)
+  "Return a service that builds the @file{/etc/environment}, which can be read
+by PAM-aware applications to set environment variables for sessions.
+
+VARS should be an association list in which both the keys and the values are
+strings or string-valued gexps."
+  (service session-environment-service-type vars))
+
+
+;;;
 ;;; Console & co.
 ;;;