121 lines
4.7 KiB
Scheme
121 lines
4.7 KiB
Scheme
;; Copyright (C) 2003 Dale Mellor
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;;
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;; This program is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.
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;;
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;; This program is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;;
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;; You should have received a copy of the GNU General Public License
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;; along with this program; if not, write to the Free Software
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;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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;; USA.
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;; This file defines the global variable current-environment-mods, and the
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;; procedures append-environment-mods (which is available to user configuration
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;; files), clear-environment-mods, modify-environment, and
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;; parse-vixie-environment. The idea is that the current-environment-mods is a
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;; list of pairs of environment names and values, and represents the cumulated
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;; environment settings in a configuration file. When a job definition is seen
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;; in a configuration file, the current-environment-mods are copied into the
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;; internal job description, and when the job actually runs these environment
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;; modifications are applied to the UNIX environment in which the job runs.
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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 one variable which the user is not allowed
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;; to control is 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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;; 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 used
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;; both implicitly by the Vixie parser, and can be used directly by users in
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;; scheme configuration files. The return value is purely for the convenience of
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;; the parse-vixie-environment procedure below.
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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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;; Procedure to act on an environment variable specification in a Vixie-style
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;; configuration file, by adding an entry to the alist above. Returns #t if the
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;; operation was successful, #f if the line could not be interpreted as an
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;; environment specification.
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(define parse-vixie-environment-regexp1
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(make-regexp
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"^[ \t]*([[:alpha:]_][[:alnum:]_]*)[ \t]*=[ \t]*\"(.*)\"[ \t]*$"))
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(define parse-vixie-environment-regexp2
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(make-regexp
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"^[ \t]*([[:alpha:]_][[:alnum:]_]*)[ \t]*=[ \t]*\'(.*)\'[ \t]*$"))
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(define parse-vixie-environment-regexp3
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(make-regexp
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"^[ \t]*([[:alpha:]_][[:alnum:]_]*)[ \t]*=[ \t]*(.*[^ \t])[ \t]*$"))
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(define parse-vixie-environment-regexp4
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(make-regexp
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"^[ \t]*([[:alpha:]_][[:alnum:]_]*)[ \t]*=[ \t]*$"))
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(use-modules (srfi srfi-2))
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(define (parse-vixie-environment string)
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(let ((match (or (regexp-exec parse-vixie-environment-regexp1 string)
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(regexp-exec parse-vixie-environment-regexp2 string)
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(regexp-exec parse-vixie-environment-regexp3 string))))
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(if match
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(append-environment-mods (match:substring match 1)
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(match:substring match 2))
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(and-let* ((match (regexp-exec parse-vixie-environment-regexp4 string)))
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(append-environment-mods (match:substring match 1) #f)))))
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