shell 支持退格

lab5/user/lab5/apps/init.c

@@ -54,15 +54,25 @@ char *readline(const char *prompt)
 		c = getch();
 		if (c < 0)
 			return NULL;
-        buf[complement_time++] = c;
-        printf("%c", c);
         if (c == '\r') {
+            // 回车
             usys_putc('\n');
             break;
+        } else if (c == '\b' || c == 127) {
+            // 退格
+            if (i > 0) {
+                i--;
+                usys_putc('\b');
+                usys_putc(' ');
+                usys_putc('\b');
+            }
+            continue;
+        } else {
+            usys_putc(c);
         }
+        buf[i++] = c;
 	}
-
-    buf[complement_time - 1] = '\0';
+    buf[i] = '\0';
 	return buf;
 }