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;; Copyright (C) 2003 Dale Mellor
;;
;; This program 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 2, or (at your option)
;; any later version.
;;
;; This program 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 this program; if not, write to the Free Software
;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
;; USA.
;; This file defines the variable current-environment-mods, and the procedures
;; append-environment-mods (which is available to user configuration files),
;; clear-environment-mods and modify-environment. The idea is that the
;; current-environment-mods is a list of pairs of environment names and values,
;; and represents the cumulated environment settings in a configuration
;; file. When a job definition is seen in a configuration file, the
;; current-environment-mods are copied into the internal job description, and
;; when the job actually runs these environment modifications are applied to the
;; UNIX environment in which the job runs.
(define-module (mcron environment)
#:export (modify-environment
clear-environment-mods
append-environment-mods
get-current-environment-mods-copy))
;; The env-alist is an association list of variable names and values. Variables
;; later in the list will take precedence over variables before. We return a
;; fixed-up version in which some variables are given specific default values
;; (which the user can override), and two variables which the user is not
;; allowed to control are added at the end of the list.
(define (impose-default-environment env-alist passwd-entry)
(append `(("HOME" . ,(passwd:dir passwd-entry))
("CWD" . ,(passwd:dir passwd-entry))
("SHELL" . ,(passwd:shell passwd-entry))
("TERM" . #f)
("TERMCAP" . #f))
env-alist
`(("LOGNAME" . ,(passwd:name passwd-entry))
("USER" . ,(passwd:name passwd-entry)))))
;; Modify the UNIX environment for the current process according to the given
;; association list of variables, with the default variable values imposed.
(define (modify-environment env-alist passwd-entry)
(for-each (lambda (variable)
(setenv (car variable) (cdr variable)))
(impose-default-environment env-alist passwd-entry)))
;; As we parse configuration files, we build up an alist of environment
;; variables here.
(define current-environment-mods '())
;; Each time a job is added to the system, we take a snapshot of the current set
;; of environment modifiers.
(define (get-current-environment-mods-copy)
(list-copy current-environment-mods))
;; When we start to parse a new configuration file, we want to start with a
;; fresh environment (actually an umodified version of the pervading mcron
;; environment).
(define (clear-environment-mods)
(set! current-environment-mods '()))
;; Procedure to add another environment setting to the alist above. This is used
;; both implicitly by the Vixie parser, and can be used directly by users in
;; scheme configuration files. The return value is purely for the convenience of
;; the parse-vixie-environment in the vixie-specification module (yuk).
(define (append-environment-mods name value)
(set! current-environment-mods (append current-environment-mods
(list (cons name value))))
#t)
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