[iproute PATCH 4/4] lib: Enable colored output only for TTYs

[Phil Sutter <phil@nwl.cc>]

Add an additional prerequisite to check_enable_color() to make sure
stdout actually points to an open TTY device. Otherwise calls like

| ip -color a s >/tmp/foo

will print color escape sequences into that file.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 lib/color.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/color.c b/lib/color.c
index edf96e5c6ecd7..500ba09682697 100644
--- a/lib/color.c
+++ b/lib/color.c
@@ -3,6 +3,7 @@
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <linux/if.h>
@@ -79,7 +80,7 @@ void enable_color(void)
 
 int check_enable_color(int color, int json)
 {
-	if (color && !json) {
+	if (color && !json && isatty(fileno(stdout))) {
 		enable_color();
 		return 0;
 	}
-- 
2.18.0