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. Allow to override this
check by specifying '-color' flag more than once.
Signed-off-by: Phil Sutter <p...@nwl.cc>
---
Changes since v1:
- Allow to override isatty() check by specifying '-color' flag more than
once.
- Document new behaviour in man pages.
---
lib/color.c | 6 +++++-
man/man8/bridge.8 | 5 ++++-
man/man8/ip.8 | 5 ++++-
man/man8/tc.8 | 5 ++++-
4 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/lib/color.c b/lib/color.c
index edf96e5c6ecd7..3a66d8ccb4b00 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 +80,10 @@ void enable_color(void)
int check_enable_color(int color, int json)
{
- if (color && !json) {
+ if (json || !color)
+ return 1;
+
+ if (color > 1 || isatty(fileno(stdout))) {
enable_color();
return 0;
}
diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
index e7f7148315e19..b865e8b6cd771 100644
--- a/man/man8/bridge.8
+++ b/man/man8/bridge.8
@@ -171,7 +171,10 @@ return code will be non zero.
.TP
.BR "\-c" , " -color"
-Use color output.
+Use color output if stdout is a terminal. Specify twice to enable color output
+irrespective of stdout state. This flag is ignored if
+.B \-json
+is also given.
.TP
.BR "\-j", " \-json"
diff --git a/man/man8/ip.8 b/man/man8/ip.8
index 0087d18b74706..c5484bbc11483 100644
--- a/man/man8/ip.8
+++ b/man/man8/ip.8
@@ -188,7 +188,10 @@ executes specified command over all objects, it depends if
command supports this
.TP
.BR "\-c" , " -color"
-Use color output.
+Use color output if stdout is a terminal. Specify twice to enable color output
+irrespective of stdout state. This flag is ignored if
+.B \-json
+is also given.
.TP
.BR "\-t" , " \-timestamp"
diff --git a/man/man8/tc.8 b/man/man8/tc.8
index 840880fbdba63..cbe7ac1847bbb 100644
--- a/man/man8/tc.8
+++ b/man/man8/tc.8
@@ -730,7 +730,10 @@ option.
.TP
.BR "\ -color"
-Use color output.
+Use color output if stdout is a terminal. Specify twice to enable color output
+irrespective of stdout state. This flag is ignored if
+.B \-json
+is also given.
.TP
.BR "\-j", " \-json"
--
2.18.0
