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@@ -13,6 +13,9 @@
 
  Major changes between "less" versions 633 and 634
 
+* Fix problem when a program piping into less reads from the tty,
+ like sudo asking for password (github #368).
+
 * Fix search modifier ^E after ^W.
 
 ======================================================================

os.c

@@ -115,7 +115,14 @@ static int check_poll(int fd, int tty)
  struct pollfd poller[2] = { { fd, POLLIN, 0 }, { tty, POLLIN, 0 } };
  int timeout = (waiting_for_data && !(scanning_eof && follow_mode == FOLLOW_NAME)) ? -1 : waiting_for_data_delay;
  if (!any_data)
+ {
+ /*
+ * Don't do polling if no data has yet been received,
+ * to allow a program piping data into less to have temporary
+ * access to the tty (like sudo asking for a password).
+ */
  return (0);
+ }
  poll(poller, 2, timeout);
 #if LESSTEST
  if (ttyin_name == NULL) /* Check for ^X only on a real tty. */
@@ -133,11 +140,6 @@ static int check_poll(int fd, int tty)
  if (ignore_eoi && exit_F_on_close && (poller[0].revents & (POLLHUP|POLLIN)) == POLLHUP)
  /* Break out of F loop on HUP due to --exit-follow-on-close. */
  return (READ_INTR);
- /*
- * Don't return READ_AGAIN if no data has yet been received,
- * to allow a program piping data into less to have temporary
- * access to the tty (like sudo asking for a password).
- */
  if ((poller[0].revents & (POLLIN|POLLHUP|POLLERR)) == 0)
  /* No data available; let caller take action, then try again. */
  return (READ_AGAIN);

version.c

@@ -982,7 +982,8 @@ v630 3/18/23 Add LESS_DATA_DELAY.
 v631 3/26/23 Fix input of dead keys on Windows.
 v632 4/6/23 Make lesstest work on MacOS; minor fixes.
 v633 5/3/23 Fix build on systems with ncurses/termcap.h or ncursesw/termcap.h.
-v634 
+v634 Allow program piping into less to access tty;
+ fix search modifier ^E after ^W.
 */
 
 char version[] = "634x";