1812205cf5
* guix/build/bournish.scm (display-tabulated): Remove #:columns and #:column-width parameters. Add #:terminal-width and #:column-gap. Compute COLUMN-WIDTH and COLUMNS.
291 lines
11 KiB
Scheme
291 lines
11 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
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;;; Copyright © 2016 Efraim Flashner <efraim@flashner.co.il>
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;;; Copyright © 2017 Ricardo Wurmus <rekado@elephly.net>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; 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 (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; 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 GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (guix build bournish)
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#:use-module (system base language)
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#:use-module (system base compile)
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#:use-module (system repl command)
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#:use-module (system repl common)
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#:use-module (ice-9 rdelim)
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#:use-module (ice-9 match)
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#:use-module (ice-9 ftw)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-11)
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#:use-module (srfi srfi-26)
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#:export (%bournish-language))
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;;; Commentary:
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;;;
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;;; This is a super minimal Bourne-like shell language for Guile. It is meant
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;;; to be used at the REPL as a rescue shell. In a way, this is to Guile what
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;;; eshell is to Emacs.
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;;;
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;;; Code:
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(define (expand-variable str)
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"Return STR or code to obtain the value of the environment variable STR
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refers to."
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;; XXX: No support for "${VAR}".
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(if (string-prefix? "$" str)
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`(or (getenv ,(string-drop str 1)) "")
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str))
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(define* (display-tabulated lst
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#:key
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(terminal-width 80)
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(column-gap 2))
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"Display the list of string LST in as many columns as needed given
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TERMINAL-WIDTH. Use COLUMN-GAP spaces between two subsequent columns."
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(define len (length lst))
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(define column-width
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;; The width of a column. Assume all the columns have the same width
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;; (GNU ls is smarter than that.)
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(+ column-gap (reduce max 0 (map string-length lst))))
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(define columns
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(max 1
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(quotient terminal-width column-width)))
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(define pad
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(if (zero? (modulo len columns))
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0
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columns))
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(define items-per-column
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(quotient (+ len pad) columns))
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(define items (list->vector lst))
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(let loop ((indexes (unfold (cut >= <> columns)
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(cut * <> items-per-column)
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1+
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0)))
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(unless (>= (first indexes) items-per-column)
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(for-each (lambda (index)
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(let ((item (if (< index len)
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(vector-ref items index)
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"")))
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(display (string-pad-right item column-width))))
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indexes)
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(newline)
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(loop (map 1+ indexes)))))
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(define ls-command-implementation
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;; Run-time support procedure.
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(case-lambda
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(()
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(display-tabulated (scandir ".")))
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(files
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(let ((files (append-map (lambda (file)
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(catch 'system-error
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(lambda ()
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(match (stat:type (lstat file))
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('directory
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;; Like GNU ls, list the contents of
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;; FILE rather than FILE itself.
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(match (scandir file
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(match-lambda
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((or "." "..") #f)
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(_ #t)))
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(#f
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(list file))
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((files ...)
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(map (cut string-append file "/" <>)
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files))))
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(_
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(list file))))
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(lambda args
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(let ((errno (system-error-errno args)))
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(format (current-error-port) "~a: ~a~%"
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file (strerror errno))
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'()))))
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files)))
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(display-tabulated files)))))
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(define (ls-command . files)
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`((@@ (guix build bournish) ls-command-implementation) ,@files))
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(define (which-command program)
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`(search-path ((@@ (guix build bournish) executable-path))
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,program))
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(define (cat-command file)
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`(call-with-input-file ,file
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(lambda (port)
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((@ (guix build utils) dump-port) port (current-output-port))
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*unspecified*)))
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(define (rm-command . args)
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"Emit code for the 'rm' command."
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(cond ((member "-r" args)
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`(for-each (@ (guix build utils) delete-file-recursively)
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(list ,@(delete "-r" args))))
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(else
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`(for-each delete-file (list ,@args)))))
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(define (lines+chars port)
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"Return the number of lines and number of chars read from PORT."
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(let loop ((lines 0) (chars 0))
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(match (read-char port)
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((? eof-object?) ;done!
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(values lines chars))
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(#\newline ;recurse
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(loop (1+ lines) (1+ chars)))
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(_ ;recurse
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(loop lines (1+ chars))))))
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(define (file-exists?* file)
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"Like 'file-exists?' but emits a warning if FILE is not accessible."
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(catch 'system-error
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(lambda ()
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(stat file))
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(lambda args
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(let ((errno (system-error-errno args)))
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(format (current-error-port) "~a: ~a~%"
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file (strerror errno))
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#f))))
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(define (wc-print file)
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(let-values (((lines chars)
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(call-with-input-file file lines+chars)))
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(format #t "~a ~a ~a~%" lines chars file)))
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(define (wc-l-print file)
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(let-values (((lines chars)
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(call-with-input-file file lines+chars)))
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(format #t "~a ~a~%" lines file)))
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(define (wc-c-print file)
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(let-values (((lines chars)
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(call-with-input-file file lines+chars)))
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(format #t "~a ~a~%" chars file)))
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(define (wc-command-implementation . files)
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(for-each wc-print (filter file-exists?* files)))
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(define (wc-l-command-implementation . files)
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(for-each wc-l-print (filter file-exists?* files)))
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(define (wc-c-command-implementation . files)
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(for-each wc-c-print (filter file-exists?* files)))
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(define (wc-command . args)
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"Emit code for the 'wc' command."
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(cond ((member "-l" args)
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`((@@ (guix build bournish) wc-l-command-implementation)
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,@(delete "-l" args)))
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((member "-c" args)
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`((@@ (guix build bournish) wc-c-command-implementation)
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,@(delete "-c" args)))
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(else
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`((@@ (guix build bournish) wc-command-implementation) ,@args))))
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(define (reboot-command . args)
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"Emit code for 'reboot'."
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;; Normally Bournish is used in the initrd, where 'reboot' is provided
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;; directly by (guile-user). In other cases, just bail out.
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`(if (defined? 'reboot)
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(reboot)
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(begin
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(format (current-error-port)
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"I don't know how to reboot, sorry about that!~%")
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#f)))
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(define (help-command . _)
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(display "\
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Hello, this is Bournish, a minimal Bourne-like shell in Guile!
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The shell is good enough to navigate the file system and run commands but not
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much beyond that. It is meant to be used as a rescue shell in the initial RAM
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disk and is probably not very useful apart from that. It has a few built-in
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commands such as 'ls' and 'cd'; it lacks globbing, pipes---everything.\n"))
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(define %not-colon (char-set-complement (char-set #\:)))
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(define (executable-path)
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"Return the search path for programs as a list."
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(match (getenv "PATH")
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(#f '())
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(str (string-tokenize str %not-colon))))
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(define %commands
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;; Built-in commands.
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`(("echo" ,(lambda strings `(list ,@strings)))
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("cd" ,(lambda (dir) `(chdir ,dir)))
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("pwd" ,(lambda () `(getcwd)))
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("rm" ,rm-command)
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("cp" ,(lambda (source dest) `(copy-file ,source ,dest)))
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("help" ,help-command)
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("ls" ,ls-command)
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("which" ,which-command)
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("cat" ,cat-command)
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("wc" ,wc-command)
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("reboot" ,reboot-command)))
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(define (read-bournish port env)
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"Read a Bournish expression from PORT, and return the corresponding Scheme
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code as an sexp."
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(match (read-line port)
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((? eof-object? eof)
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eof)
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((= string-tokenize (command args ...))
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(match (assoc command %commands)
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((command proc) ;built-in command
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(apply proc (map expand-variable args)))
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(#f
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(let ((command (if (string-prefix? "\\" command)
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(string-drop command 1)
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command)))
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`(system* ,command ,@(map expand-variable args))))))))
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(define %bournish-language
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(let ((scheme (lookup-language 'scheme)))
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;; XXX: The 'scheme' language lacks a "joiner", so we add one here. This
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;; allows us to have 'read-bournish' read one shell statement at a time
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;; instead of having to read until EOF.
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(set! (language-joiner scheme)
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(lambda (exps env)
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(match exps
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(() '(begin))
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((exp) exp)
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(_ `(begin ,@exps)))))
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(make-language #:name 'bournish
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#:title "Bournish"
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;; The reader does all the heavy lifting.
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#:reader read-bournish
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#:compilers `((scheme . ,(lambda (exp env options)
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(values exp env env))))
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#:decompilers '()
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#:evaluator (language-evaluator scheme)
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#:printer (language-printer scheme)
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#:make-default-environment
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(language-make-default-environment scheme))))
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;; XXX: ",L bournish" won't work unless we call our module (language bournish
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;; spec), which is kinda annoying, so provide another meta-command.
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(define-meta-command ((bournish guix) repl)
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"bournish
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Switch to the Bournish language."
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(let ((current (repl-language repl)))
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(format #t "Welcome to ~a, a minimal Bourne-like shell!~%To switch back, type `,L ~a'.\n"
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(language-title %bournish-language)
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(language-name current))
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(current-language %bournish-language)
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(set! (repl-language repl) %bournish-language)))
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;;; bournish.scm ends here
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