From f1504c0c26835d89ec4f7176ec1536d467bbf6b0 Mon Sep 17 00:00:00 2001
From: Edward Tomasz Napierala <trasz@FreeBSD.org>
Date: Mon, 8 May 2017 08:58:51 +0000
Subject: [PATCH] Add resizewin -z. It makes resizewin not do anything if the
 terminal size is already set to something other than zero. It's supposed to
 be called from eg /etc/profile - it's not neccessary to query terminal size
 when logging in over the network, because the protocol used already takes
 care of this, but it's neccessary when logging over a serial line.

Reviewed by:	cem, Daniel O'Connor <darius@dons.net.au>
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D10637
---
 usr.bin/resizewin/resizewin.1 | 12 +++++++++++-
 usr.bin/resizewin/resizewin.c | 34 ++++++++++++++++++++++++++++++++--
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/usr.bin/resizewin/resizewin.1 b/usr.bin/resizewin/resizewin.1
index b7376c79026..ce15ce70283 100644
--- a/usr.bin/resizewin/resizewin.1
+++ b/usr.bin/resizewin/resizewin.1
@@ -27,17 +27,27 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 9, 2016
+.Dd May 8, 2017
 .Dt RESIZEWIN 1
 .Os
 .Sh NAME
 .Nm resizewin
 .Nd update the kernel window size for the current TTY
+.Sh SYNOPSIS
+.Nm
+.Op Fl z
 .Sh DESCRIPTION
 Query the terminal emulator window size with the
 .Dv TIOCSWINSZ
 ioctl and set the window size known by the kernel to the new values.
 The terminal is assumed to be VT100/ANSI compatible.
+.Pp
+The following options are available:
+.Bl -tag -width ".Fl z"
+.It Fl z
+Do nothing unless the current kernel terminal size is zero.
+.El
+.Pp
 .Nm
 is functionally similar to
 .Xr resize 1 ,
diff --git a/usr.bin/resizewin/resizewin.c b/usr.bin/resizewin/resizewin.c
index 566577be4d7..20116b61508 100644
--- a/usr.bin/resizewin/resizewin.c
+++ b/usr.bin/resizewin/resizewin.c
@@ -47,20 +47,50 @@ static const char query[] =
     "\033[999;999H"	/* Move cursor */
     "\033[6n"		/* Get cursor position */
     "\0338";		/* Restore cursor position */
+
+static void
+usage(void)
+{
+
+	fprintf(stderr, "usage: resizewin [-z]\n");
+	exit(1);
+}
+
 int
-main(__unused int argc, __unused char **argv)
+main(int argc, char **argv)
 {
 	struct termios old, new;
 	struct winsize w;
-	int ret, fd, cnt, error;
+	int ret, fd, ch, cnt, error, zflag;
 	char data[20];
 	struct timeval then, now;
 
 	error = 0;
+	zflag = 0;
+	while ((ch = getopt(argc, argv, "z")) != -1) {
+		switch (ch) {
+		case 'z':
+			zflag = 1;
+			break;
+		case '?':
+		default:
+			usage();
+		}
+	}
+	argc -= optind;
+	if (argc != 0)
+		usage();
 
 	if ((fd = open("/dev/tty", O_RDWR | O_NONBLOCK)) == -1)
 		exit(1);
 
+	if (zflag) {
+		if (ioctl(fd, TIOCGWINSZ, &w) == -1)
+			exit(1);
+		if (w.ws_row != 0 && w.ws_col != 0)
+			exit(0);
+	}
+
 	/* Disable echo */
 	if (tcgetattr(fd, &old) == -1)
 		exit(1);