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From c8df315c742fc470e766244ce8efe305a98d720a Mon Sep 17 00:00:00 2001
From: Mark Nudelman <markn@greenwoodsoftware.com>
Date: Sun, 28 May 2023 15:28:42 -0700
Subject: [PATCH] Avoid stealing data from an input program that uses the tty
 at startup, like sudo.

---
 os.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/os.c b/os.c
index af95834..7206277 100644
--- a/os.c
+++ b/os.c
@@ -114,6 +114,8 @@ 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)
+		return (0);
 	poll(poller, 2, timeout);
 #if LESSTEST
 	if (ttyin_name == NULL) /* Check for ^X only on a real tty. */
@@ -136,7 +138,7 @@ static int check_poll(int fd, int tty)
 	 * to allow a program piping data into less to have temporary
 	 * access to the tty (like sudo asking for a password).
 	 */
-	if (any_data && (poller[0].revents & (POLLIN|POLLHUP|POLLERR)) == 0)
+	if ((poller[0].revents & (POLLIN|POLLHUP|POLLERR)) == 0)
 		/* No data available; let caller take action, then try again. */
 		return (READ_AGAIN);
 	/* There is data (or HUP/ERR) available. Safe to call read() without blocking. */
-- 
2.33.0