2018-07-12 03:05:15 +01:00
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;;; The Geesh Shell Interpreter
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;;; Copyright 2018 Timothy Sample <samplet@ngyro.com>
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;;;
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;;; This file is part of Geesh.
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;;;
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;;; Geesh 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 3 of the License, or
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;;; (at your option) any later version.
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;;;
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;;; Geesh 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 Geesh. If not, see <http://www.gnu.org/licenses/>.
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(define-module (geesh word)
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#:use-module (geesh environment)
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#:use-module (ice-9 match)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-26)
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#:export (eval-cmd-sub
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expand-word))
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;;; Commentary:
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;;;
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;;; This module contains functions for manipulating shell words. This
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;;; includes tilde expansion, parameter expansions, field splitting,
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;;; globbing, etc.
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;;;
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;;; In the code below, the term "qword" is used to refer to words that
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;;; only contain quotations (i.e., no substitutions).
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;;;
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;;; Code:
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(define (normalize-word word)
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"Normalize @var{word} (which may be a word or a qword) so that it is
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guaranteed to be a list."
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(match word
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((? string?) (list word))
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(((? symbol?) _) (list word))
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(_ word)))
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(define (infix x xs)
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"Place @var{x} between each element of the list @var{xs}."
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(if (null? xs)
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xs
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(let loop ((xs (cdr xs)) (acc (list (car xs))))
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(if (null? xs)
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(reverse acc)
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(loop (cdr xs) (cons* (car xs) x acc))))))
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(define (list-split xs sym)
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"Split the list @var{xs} into sublists delimited by the symbol
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@var{sym}."
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(let loop ((xs xs) (small-acc '()) (big-acc '()))
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(cond
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((null? xs)
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(reverse (cons (reverse small-acc) big-acc)))
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((eq? (car xs) sym)
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(loop (cdr xs) '() (cons (reverse small-acc) big-acc)))
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(else
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(loop (cdr xs) (cons (car xs) small-acc) big-acc)))))
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(define (split-fields qword ifs)
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"Split @var{qword} into a list of qwords delimited by the character
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set @var{ifs}."
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(define (wedge-apart qword-part ifs)
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(match qword-part
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(('<sh-quote> _) (list qword-part))
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("" '(""))
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(str (let ((str-parts (string-split str ifs)))
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(if (every string-null? str-parts)
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'(wedge)
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2018-07-18 07:33:08 +01:00
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(filter (lambda (x)
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(or (eq? x 'wedge) (not (string-null? x))))
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(infix 'wedge str-parts)))))))
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2018-07-12 03:05:15 +01:00
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(let ((wedged (append-map (cut wedge-apart <> ifs)
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(normalize-word qword))))
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2018-07-18 07:33:08 +01:00
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(filter pair? (list-split wedged 'wedge))))
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2018-07-12 03:05:15 +01:00
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(define (remove-quotes qword)
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"Remove quote forms from @var{qword} and concatenate the result into a
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single field (string)."
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(let loop ((qword (normalize-word qword)) (acc '()))
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(match qword
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(() (string-concatenate-reverse acc))
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((('<sh-quote> qword*) . t) (loop t (cons (remove-quotes qword*) acc)))
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(((? string? h) . t) (loop t (cons h acc))))))
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(define eval-cmd-sub
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;; A procedure for evaluating (expanding) a command substitution.
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;; This is parameterized to avoid a circular dependency.
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(make-parameter (lambda (exps) (throw 'eval-cmd-sub-unset))))
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(define (string-not-null? str)
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"Check if @var{str} is a non-null string."
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(and (string? str) (not (string-null? str))))
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(define (word->qword env word)
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"Convert @var{word} into a qword by resolving all parameter, command,
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and arithmetic substitions using the environment @var{env}."
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(match word
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((? string?)
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word)
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(('<sh-quote> quoted-word)
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`(<sh-quote> ,(word->qword env quoted-word)))
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(('<sh-cmd-sub> . exps)
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((eval-cmd-sub) exps))
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(('<sh-ref> name)
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2018-07-17 03:48:47 +01:00
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(var-ref* env name))
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2018-07-12 03:05:15 +01:00
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(('<sh-ref-or> name default)
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(or (var-ref env name)
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(word->qword env (or default ""))))
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(('<sh-ref-or*> name default)
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(let ((value (var-ref env name)))
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(if (string-not-null? value)
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value
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(word->qword env (or default "")))))
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(('<sh-ref-or!> name default)
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(or (var-ref env name)
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(let ((new-value (expand-word env (or default "")
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#:split? #f #:rhs-tildes? #t)))
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(set-var! env name new-value)
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new-value)))
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(('<sh-ref-or!*> name default)
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(let ((value (var-ref env name)))
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(if (string-not-null? value)
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value
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(let ((new-value (expand-word env (or default "")
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#:split? #f #:rhs-tildes? #t)))
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(set-var! env name new-value)
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new-value))))
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(('<sh-ref-assert> name message) (error "Not implemented"))
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(('<sh-ref-assert*> name message) (error "Not implemented"))
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(('<sh-ref-and> name value)
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(if (string-not-null? (var-ref env name))
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(word->qword env (or value ""))
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""))
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(('<sh-ref-and*> name value)
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(or (and (var-ref env name)
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(word->qword env (or value "")))
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""))
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(('<sh-ref-except-min> name pattern) (error "Not implemented"))
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(('<sh-ref-except-max> name pattern) (error "Not implemented"))
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(('<sh-ref-skip-min> name pattern) (error "Not implemented"))
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(('<sh-ref-skip-max> name pattern) (error "Not implemented"))
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(('<sh-ref-length> name)
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2018-07-17 03:48:47 +01:00
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(number->string (string-length (var-ref* env name))))
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2018-07-12 03:05:15 +01:00
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(_ (map (cut word->qword env <>) word))))
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(define* (expand-word env word #:key (split? #t) (rhs-tildes? #f))
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"Expand @var{word} into a list of fields using the environment
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@var{env}."
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(let ((qword (word->qword env word)))
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(if split?
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(map remove-quotes
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(split-fields qword (char-set #\newline #\tab #\space)))
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(remove-quotes qword))))
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