From 216c4b811a5a19157ce9843527ec2f96517c6699 Mon Sep 17 00:00:00 2001
From: David Adam <zanchey@ucc.gu.uwa.edu.au>
Date: Mon, 16 Oct 2017 12:13:30 +0800
Subject: [PATCH] only call ioctl to export new termsize if process is in the
 foreground

Closes #4477.
---
 src/common.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/common.cpp b/src/common.cpp
index d212e200b..9d78b5f59 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -1592,7 +1592,10 @@ static void export_new_termsize(struct winsize *new_termsize) {
     env_set_one(L"LINES", ENV_GLOBAL | (lines.missing_or_empty() ? ENV_DEFAULT : ENV_EXPORT), buf);
 
 #ifdef HAVE_WINSIZE
-    ioctl(STDOUT_FILENO, TIOCSWINSZ, new_termsize);
+    // Only write the new terminal size if we are in the foreground (#4477)
+    if (tcgetpgrp(STDOUT_FILENO) == getpgrp()) {
+        ioctl(STDOUT_FILENO, TIOCSWINSZ, new_termsize);
+    }
 #endif
 }