105 lines
3.7 KiB
Scheme
105 lines
3.7 KiB
Scheme
;; Copyright (C) 2003 Dale Mellor
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;;
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;; This file is part of GNU mcron.
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;;
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;; GNU mcron is free software: you can redistribute it and/or modify it under
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;; the terms of the GNU General Public License as published by the Free
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;; Software Foundation, either version 3 of the License, or (at your option)
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;; any later version.
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;;
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;; GNU mcron is distributed in the hope that it will be useful, but WITHOUT
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;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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;; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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;; more details.
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;;
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;; You should have received a copy of the GNU General Public License along
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;; with GNU mcron. If not, see <http://www.gnu.org/licenses/>.
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;; This file defines the variable current-environment-mods, and the procedures
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;; append-environment-mods (which is available to user configuration files),
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;; clear-environment-mods and modify-environment. The idea is that the
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;; current-environment-mods is a list of pairs of environment names and values,
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;; and represents the cumulated environment settings in a configuration
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;; file. When a job definition is seen in a configuration file, the
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;; current-environment-mods are copied into the internal job description, and
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;; when the job actually runs these environment modifications are applied to
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;; the UNIX environment in which the job runs.
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(define-module (mcron environment)
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#:export (modify-environment
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clear-environment-mods
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append-environment-mods
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get-current-environment-mods-copy))
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;; The env-alist is an association list of variable names and values. Variables
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;; later in the list will take precedence over variables before. We return a
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;; fixed-up version in which some variables are given specific default values
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;; (which the user can override), and two variables which the user is not
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;; allowed to control are added at the end of the list.
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(define (impose-default-environment env-alist passwd-entry)
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(append `(("HOME" . ,(passwd:dir passwd-entry))
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("CWD" . ,(passwd:dir passwd-entry))
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("SHELL" . ,(passwd:shell passwd-entry))
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("TERM" . #f)
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("TERMCAP" . #f))
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env-alist
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`(("LOGNAME" . ,(passwd:name passwd-entry))
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("USER" . ,(passwd:name passwd-entry)))))
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;; Modify the UNIX environment for the current process according to the given
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;; association list of variables, with the default variable values imposed.
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(define (modify-environment env-alist passwd-entry)
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(for-each (lambda (variable)
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(setenv (car variable) (cdr variable)))
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(impose-default-environment env-alist passwd-entry)))
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;; As we parse configuration files, we build up an alist of environment
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;; variables here.
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(define current-environment-mods '())
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;; Each time a job is added to the system, we take a snapshot of the current
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;; set of environment modifiers.
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(define (get-current-environment-mods-copy)
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(list-copy current-environment-mods))
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;; When we start to parse a new configuration file, we want to start with a
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;; fresh environment (actually an umodified version of the pervading mcron
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;; environment).
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(define (clear-environment-mods)
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(set! current-environment-mods '()))
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;; Procedure to add another environment setting to the alist above. This is
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;; used both implicitly by the Vixie parser, and can be used directly by users
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;; in scheme configuration files. The return value is purely for the
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;; convenience of the parse-vixie-environment in the vixie-specification module
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;; (yuk).
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(define (append-environment-mods name value)
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(set! current-environment-mods (append current-environment-mods
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(list (cons name value))))
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#t)
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