Re: Adding wc to Bournish

[Efraim Flashner <efraim@flashner.co.il>]

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I've been working more on this and I think it's much better now.
Currently it checks for `-l' or `-c' flags in the first position and
with some borrowing of code from the ls-command I've worked out
returning an error (out of order) when a file doesn't exist. And if
there's no flag then it attempts to read the first argument as a file
also.

bournish@(guile-user)> wc -l gpl-3.0.txt foo guix_cve
foo: No such file or directory
674 gpl-3.0.txt
25 guix_cve


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Efraim Flashner   <efraim@flashner.co.il>   אפרים פלשנר
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From 0c37b8106ca8cf65e86029bdf89dfe50b7df8f87 Mon Sep 17 00:00:00 2001
From: Efraim Flashner <efraim@flashner.co.il>
Date: Sun, 22 May 2016 14:56:06 +0300
Subject: [PATCH] Bournish: Add `wc' command.

* guix/build/bournish.scm (%commands): Add wc command.
---
 guix/build/bournish.scm | 63 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 62 insertions(+), 1 deletion(-)

diff --git a/guix/build/bournish.scm b/guix/build/bournish.scm
index 4022796..480ce5f 100644
--- a/guix/build/bournish.scm
+++ b/guix/build/bournish.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2016 Efraim Flashner <efraim@flashner.co.il>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -25,7 +26,9 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 ftw)
   #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-26)
+  #:use-module (srfi srfi-41)
   #:export (%bournish-language))
 
 ;;; Commentary:
@@ -103,6 +106,63 @@ characters."
        ((@ (guix build utils) dump-port) port (current-output-port))
        *unspecified*)))
 
+(define (file-size file)
+    (stat:size (stat file)))
+
+(define (wc-c-command file)
+  ;; Faster when only `wc -c' is called
+  (file-size file))
+
+(define (wc-l-command file)
+  ;; Faster when only `wc -l' is called
+  (stream-length
+    (stream-filter
+      (lambda (chr)
+        (char=? chr #\newline))
+      (port->stream (open-file file "r")))))
+
+(define (lines+chars port)
+  ;; Return the number of lines and number of chars read from PORT.
+  ;; TODO: Also return the number of words.
+  (let loop ((lines 0) (chars 0))
+    (match (read-char port) ; get the next char ready
+      ((? eof-object?)              ;done!
+       (values lines chars))
+      (#\newline                    ;recurse
+       (loop (1+ lines) (1+ chars)))
+      (_                            ;recurse
+       (loop lines (1+ chars))))))
+
+(define* (wc-command-implementation file #:optional args)
+  (let-values (((lines chars)
+                (call-with-input-file file lines+chars)))
+    (match args
+      (#\l
+       (format #t "~a ~a~%" lines file))
+      (#\c
+       (format #t "~a ~a~%" chars file))
+      (_
+       (format #t "~a ~a ~a~%" lines chars file)))))
+
+(define (wc-command args . rest)
+  (let* ((flags (cond ((string=? args "-l") #\l)
+                      ((string=? args "-c") #\c)
+                      (else #\nul)))    ; no flags, "args" is a file
+         (files (filter (lambda (file)
+                          (catch 'system-error
+                            (lambda ()
+                              (lstat file))
+                            (lambda args
+                               (let ((errno (system-error-errno args)))
+                                (format (current-error-port) "~a: ~a~%"
+                                        file (strerror errno))
+                                #f))))
+                        (if (char=? flags #\nul) (cons args rest) rest))))
+    (for-each
+      (lambda (file)
+        ((@@ (guix build bournish) wc-command-implementation) file flags))
+    files)))
+
 (define (help-command . _)
   (display "\
 Hello, this is Bournish, a minimal Bourne-like shell in Guile!
@@ -129,7 +189,8 @@ commands such as 'ls' and 'cd'; it lacks globbing, pipes---everything.\n"))
     ("help"   ,help-command)
     ("ls"     ,ls-command)
     ("which"  ,which-command)
-    ("cat"    ,cat-command)))
+    ("cat"    ,cat-command)
+    ("wc"     ,wc-command)))
 
 (define (read-bournish port env)
   "Read a Bournish expression from PORT, and return the corresponding Scheme
-- 
2.8.3


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