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;; Copyright (C) 2003 Dale Mellor
;;
;; This file is part of GNU mcron.
;;
;; GNU mcron 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 mcron 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 mcron. If not, see <http://www.gnu.org/licenses/>.
;; 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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