Make colored output configurable

Allow for -color={never,auto,always} to have colored output disabled,
enabled only if stdout is a terminal or enabled regardless of stdout
state.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

bridge/bridge.c

@@ -173,8 +173,7 @@ main(int argc, char **argv)
 			NEXT_ARG();
 			if (netns_switch(argv[1]))
 				exit(-1);
-		} else if (matches(opt, "-color") == 0) {
-			++color;
+		} else if (matches_color(opt, &color)) {
 		} else if (matches(opt, "-compressvlans") == 0) {
 			++compress_vlans;
 		} else if (matches(opt, "-force") == 0) {

include/color.h

@@ -2,6 +2,8 @@
 #ifndef __COLOR_H__
 #define __COLOR_H__ 1
 
+#include <stdbool.h>
+
 enum color_attr {
 	COLOR_IFNAME,
 	COLOR_MAC,
@@ -12,8 +14,15 @@ enum color_attr {
 	COLOR_NONE
 };
 
+enum color_opt {
+	COLOR_OPT_NEVER = 0,
+	COLOR_OPT_AUTO = 1,
+	COLOR_OPT_ALWAYS = 2
+};
+
 void enable_color(void);
 int check_enable_color(int color, int json);
+bool matches_color(const char *arg, int *val);
 void set_color_palette(void);
 int color_fprintf(FILE *fp, enum color_attr attr, const char *fmt, ...);
 enum color_attr ifa_family_color(__u8 ifa_family);

ip/ip.c

@@ -283,8 +283,7 @@ int main(int argc, char **argv)
 				exit(-1);
 			}
 			rcvbuf = size;
-		} else if (matches(opt, "-color") == 0) {
-			++color;
+		} else if (matches_color(opt, &color)) {
 		} else if (matches(opt, "-help") == 0) {
 			usage();
 		} else if (matches(opt, "-netns") == 0) {

lib/color.c

@@ -3,11 +3,13 @@
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <linux/if.h>
 
 #include "color.h"
+#include "utils.h"
 
 enum color {
 	C_RED,
@@ -79,13 +81,42 @@ void enable_color(void)
 
 int check_enable_color(int color, int json)
 {
-	if (color && !json) {
+	if (json || color == COLOR_OPT_NEVER)
+		return 1;
+
+	if (color == COLOR_OPT_ALWAYS || isatty(fileno(stdout))) {
 		enable_color();
 		return 0;
 	}
 	return 1;
 }
 
+bool matches_color(const char *arg, int *val)
+{
+	char *dup, *p;
+
+	if (!val)
+		return false;
+
+	dup = strdupa(arg);
+	p = strchrnul(dup, '=');
+	if (*p)
+		*(p++) = '\0';
+
+	if (matches(dup, "-color"))
+		return false;
+
+	if (*p == '\0' || !strcmp(p, "always"))
+		*val = COLOR_OPT_ALWAYS;
+	else if (!strcmp(p, "auto"))
+		*val = COLOR_OPT_AUTO;
+	else if (!strcmp(p, "never"))
+		*val = COLOR_OPT_NEVER;
+	else
+		return false;
+	return true;
+}
+
 void set_color_palette(void)
 {
 	char *p = getenv("COLORFGBG");

man/man8/bridge.8

@@ -172,8 +172,17 @@ If there were any errors during execution of the commands, the application
 return code will be non zero.
 
 .TP
-.BR "\-c" , " -color"
-Use color output.
+.BR \-c [ color ][ = { always | auto | never }
+Configure color output. If parameter is omitted or
+.BR always ,
+color output is enabled regardless of stdout state. If parameter is
+.BR auto ,
+stdout is checked to be a terminal before enabling color output. If parameter is
+.BR never ,
+color output is disabled. If specified multiple times, the last one takes
+precedence. This flag is ignored if
+.B \-json
+is also given.
 
 .TP
 .BR "\-j", " \-json"

man/man8/ip.8

@@ -187,8 +187,17 @@ to
 executes specified command over all objects, it depends if command supports this option.
 
 .TP
-.BR "\-c" , " -color"
-Use color output.
+.BR \-c [ color ][ = { always | auto | never }
+Configure color output. If parameter is omitted or
+.BR always ,
+color output is enabled regardless of stdout state. If parameter is
+.BR auto ,
+stdout is checked to be a terminal before enabling color output. If parameter is
+.BR never ,
+color output is disabled. If specified multiple times, the last one takes
+precedence. This flag is ignored if
+.B \-json
+is also given.
 
 .TP
 .BR "\-t" , " \-timestamp"

man/man8/tc.8

@@ -755,8 +755,17 @@ option was specified. Classes can be filtered only by
 option.
 
 .TP
-.BR "\ -color"
-Use color output.
+.BR \-c [ color ][ = { always | auto | never }
+Configure color output. If parameter is omitted or
+.BR always ,
+color output is enabled regardless of stdout state. If parameter is
+.BR auto ,
+stdout is checked to be a terminal before enabling color output. If parameter is
+.BR never ,
+color output is disabled. If specified multiple times, the last one takes
+precedence. This flag is ignored if
+.B \-json
+is also given.
 
 .TP
 .BR "\-j", " \-json"

tc/tc.c

@@ -496,8 +496,7 @@ int main(int argc, char **argv)
 				matches(argv[1], "-conf") == 0) {
 			NEXT_ARG();
 			conf_file = argv[1];
-		} else if (matches(argv[1], "-color") == 0) {
-			++color;
+		} else if (matches_color(argv[1], &color)) {
 		} else if (matches(argv[1], "-timestamp") == 0) {
 			timestamp++;
 		} else if (matches(argv[1], "-tshort") == 0) {