lineedit: add support for M-b, M-f, M-d, M-Backspace

function                                             old     new   delta
ctrl_left                                              -      96     +96
ctrl_right                                             -      76     +76
static.esccmds                                        81      93     +12
read_line_input                                     3876    3885      +9
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 2/0 up/down: 193/0)             Total: 193 bytes

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

1 files changed, 40 insertions, 0 deletions

diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 603bbfcae..0d232889b 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -2504,6 +2504,44 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
                                 vi_cmdmode = 1;
                                 input_backward(1);
                         }
+                        /* Handle a few ESC-<key> combinations the same way
+                         * standard readline bindings (IOW: bash) do.
+                         * Often, Alt-<key> generates ESC-<key>.
+                         */
+                        ic = lineedit_read_key(read_key_buffer, timeout);
+                        switch (ic) {
+                                //case KEYCODE_LEFT: - bash doesn't do this
+                                case 'b':
+                                        ctrl_left();
+                                        break;
+                                //case KEYCODE_RIGHT: - bash doesn't do this
+                                case 'f':
+                                        ctrl_right();
+                                        break;
+                                //case KEYCODE_DELETE: - bash doesn't do this
+                                case 'd':  /* Alt-D */
+                                {
+                                        /* Delete word forward */
+                                        int nc, sc = cursor;
+                                        ctrl_right();
+                                        nc = cursor;
+                                        input_backward(cursor - sc);
+                                        while (--nc >= cursor)
+                                                input_delete(1);
+                                        break;
+                                }
+                                case '\b':   /* Alt-Backspace(?) */
+                                case '\x7f': /* Alt-Backspace(?) */
+                                //case 'w': - bash doesn't do this
+                                {
+                                        /* Delete word backward */
+                                        int sc = cursor;
+                                        ctrl_left();
+                                        while (sc-- > cursor)
+                                                input_delete(1);
+                                        break;
+                                }
+                        }
                         break;
 #endif /* FEATURE_COMMAND_EDITING_VI */
 
@@ -2532,9 +2570,11 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
                         input_backward(1);
                         break;
                 case KEYCODE_CTRL_LEFT:
+                case KEYCODE_ALT_LEFT: /* bash doesn't do it */
                         ctrl_left();
                         break;
                 case KEYCODE_CTRL_RIGHT:
+                case KEYCODE_ALT_RIGHT: /* bash doesn't do it */
                         ctrl_right();
                         break;
                 case KEYCODE_HOME: