fix(sysdig): address review comments

Signed-off-by: Roberto Scolaro <roberto.scolaro21@gmail.com>

userspace/sysdig/sysdig.cpp

@@ -72,6 +72,12 @@ static std::atomic<bool> g_plugin_input = false;
 std::vector<sinsp_chisel*> g_chisels;
 #endif
 
+enum color_term_out {
+  COLOR = 0,
+  NO_COLOR,
+  FORCE_COLOR
+};
+
 static void usage();
 
 //
@@ -290,7 +296,8 @@ static void usage()
 " -M <num_seconds>   Stop collecting after <num_seconds> reached.\n"
 " -n <num>, --numevents=<num>\n"
 "                    Stop capturing after <num> events\n"
-" --no-color         Avoid using colors on terminal output.\n"
+" --color <true|force|false> \n"
+"                    Set colors settings on terminal output.\n"
 " --page-faults      Capture user/kernel major/minor page faults\n"
 " --plugin-config-file\n"
 "                    Load the plugin configuration from a Falco-compatible yaml file.\n"
@@ -962,6 +969,15 @@ void disable_tty_echo() {
 }
 #endif
 
+static inline bool stdout_supports_color()
+{
+#ifdef _WIN32
+    return false;
+#else
+    return isatty(fileno(stdout));
+#endif
+}
+
 std::string escape_output_format(const std::string& s)
 {
     std::stringstream  ss{""};
@@ -1038,7 +1054,7 @@ sysdig_init_res sysdig_init(int argc, char **argv)
 	sinsp_opener opener;
 	std::unique_ptr<filter_check_list> filter_list;
 	std::shared_ptr<sinsp_filter_factory> filter_factory;
-	bool no_color_flag = false;
+	color_term_out color_flag = COLOR;
 
 	// These variables are for the cycle_writer engine
 	int duration_seconds = 0;
@@ -1112,7 +1128,7 @@ sysdig_init_res sysdig_init(int argc, char **argv)
 		{"print-hex", no_argument, 0, 'x'},
 		{"print-hex-ascii", no_argument, 0, 'X'},
 		{"compress", no_argument, 0, 'z' },
-		{"no-color", no_argument, 0, 0 },
+		{"color", required_argument, 0, 0 },
 		{0, 0, 0, 0}
 	};
 
@@ -1631,9 +1647,26 @@ sysdig_init_res sysdig_init(int argc, char **argv)
 						return sysdig_init_res(EXIT_SUCCESS);
 					}
 
-					else if (optname == "no-color")
+					else if (optname == "color")
 					{
-						no_color_flag = true;
+						auto color_state = std::string(optarg);
+						if (color_state == "true")
+						{
+							color_flag = COLOR;
+						}
+						else if (color_state == "force")
+						{
+							color_flag = FORCE_COLOR;
+						}
+						else if (color_state == "false")
+						{
+							color_flag = NO_COLOR;
+						}
+						else
+						{
+							fprintf(stderr, "invalid color mode for flag --color\n");
+							return sysdig_init_res(EXIT_FAILURE);
+						}
 					}
 				}
 				break;
@@ -1646,16 +1679,14 @@ sysdig_init_res sysdig_init(int argc, char **argv)
 			}
 		}
 
-#ifndef _WIN32
-	char* no_color = getenv("NO_COLOR");
-	if (isatty(fileno(stdout)) &&
-		(no_color != nullptr && strcmp(no_color, "1") != 0) && !no_color_flag)
+	char* no_color_env = getenv("NO_COLOR");
+        if ((color_flag == FORCE_COLOR) ||
+            (stdout_supports_color() && (no_color_env != nullptr && no_color_env[0] != '\0') && color_flag == COLOR))
 	{
 		output_format = R"(*%evt.num %evt.outputtime %evt.cpu \e[01;32m%proc.name\e[00m (\e[01;36m%proc.pid\e[00m.%thread.tid) %evt.dir \e[01;34m%evt.type\e[00m %evt.info)";
 		output_format_plugin = R"(*%evt.num %evt.datetime.s [\e[01;32m%evt.pluginname\e[00m] %evt.plugininfo)";
 	}
 	else
-#endif
 	{
 		output_format = "*%evt.num %evt.outputtime %evt.cpu %proc.name (%thread.tid) %evt.dir %evt.type %evt.info";
 		output_format_plugin = "*%evt.num %evt.datetime.s [%evt.pluginname] %evt.plugininfo";