ash,hush: properly handle ${v//pattern/repl} if pattern starts with /

Closes 2695

function                                             old     new   delta
parse_dollar                                         762     790     +28
subevalvar                                          1258    1267      +9
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 37/0)               Total: 37 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/shell/hush.c b/shell/hush.c
index 6852b5f79..3407711cd 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -4930,6 +4930,15 @@ static int parse_dollar(o_string *as_string,
                                         end_ch = '}' * 0x100 + '/';
                                 }
                                 o_addchr(dest, ch);
+                                /* The pattern can't be empty.
+                                 * IOW: if the first char after "${v//" is a slash,
+                                 * it does not terminate the pattern - it's the first char of the pattern:
+                                 *  v=/dev/ram; echo ${v////-}  prints -dev-ram (pattern is "/")
+                                 *  v=/dev/ram; echo ${v///r/-} prints /dev-am  (pattern is "/r")
+                                 */
+                                if (i_peek(input) == '/') {
+                                        o_addchr(dest, i_getch(input));
+                                }
  again:
                                 if (!BB_MMU)
                                         pos = dest->length;