From ab52d02963fcb0aecd8089ddc5cdc4d783092a4b Mon Sep 17 00:00:00 2001
From: Jonathan Clairembault <jonathan@clairembault.fr>
Date: Fri, 23 Nov 2012 09:24:53 +0100
Subject: expand: handle backspace.

---
 scripts/test/expand.test | 1 +
 toys/posix/expand.c      | 7 ++++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/scripts/test/expand.test b/scripts/test/expand.test
index 73374562..bb0ca083 100644
--- a/scripts/test/expand.test
+++ b/scripts/test/expand.test
@@ -11,6 +11,7 @@ testing "expand default" "expand input" "        foo     bar\n" "\tfoo\tbar\n" "
 testing "expand default stdin" "expand"  "        foo     bar\n" "" "\tfoo\tbar\n"
 testing "expand single" "expand -t 2 input" "  foo bar\n" "\tfoo\tbar\n" ""
 testing "expand tablist" "expand -t 5,10,12 input" "     foo  bar foo\n" "\tfoo\tbar\tfoo\n" ""
+testing "expand backspace" "expand input" "foobarf bar\n" "foobarfoo\b\b\tbar\n" ""
 
 # advanced tests
 
diff --git a/toys/posix/expand.c b/toys/posix/expand.c
index 739c326d..bbe6fdf1 100644
--- a/toys/posix/expand.c
+++ b/toys/posix/expand.c
@@ -1,6 +1,4 @@
 /* expand.c - expands tabs to space
- *
- * FIXME: handle backspace.
  *
  * Copyright 2012 Jonathan Clairembault <jonathan at clairembault dot fr>
  *
@@ -116,7 +114,10 @@ static void expand_file(int fd, char *name)
         wrlinei += count;
       } else { /* copy input to output */
         wrbuf[wrbufi++] = rdbuf[rdbufi];
-        wrlinei += 1;
+        if (rdbuf[rdbufi] == '\b') /* go back one column on backspace */
+          wrlinei -= !!wrlinei; /* do not go below zero */
+        else
+          wrlinei += 1;
         /* flush expand buffer and reset tablist at newline */
         if (rdbuf[rdbufi] == '\n') {
           writeall(STDOUT_FILENO, wrbuf, wrbufi);
-- 
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