Add handling of environment variables to control terminal/logging colors (#12641)

src/main.cpp

@@ -77,12 +77,17 @@ extern "C" {
 #define DEBUGFILE "debug.txt"
 #define DEFAULT_SERVER_PORT 30000
 
+#define ENV_NO_COLOR "NO_COLOR"
+#define ENV_CLICOLOR "CLICOLOR"
+#define ENV_CLICOLOR_FORCE "CLICOLOR_FORCE"
+
 typedef std::map<std::string, ValueSpec> OptionList;
 
 /**********************************************************************
  * Private functions
  **********************************************************************/
 
+static void get_env_opts(Settings &args);
 static bool get_cmdline_opts(int argc, char *argv[], Settings *cmd_args);
 static void set_allowed_options(OptionList *allowed_options);
 
@@ -136,6 +141,7 @@ int main(int argc, char *argv[])
 	g_logger.addOutputMaxLevel(&stderr_output, LL_ACTION);
 
 	Settings cmd_args;
+	get_env_opts(cmd_args);
 	bool cmd_args_ok = get_cmdline_opts(argc, argv, &cmd_args);
 	if (!cmd_args_ok
 			|| cmd_args.getFlag("help")
@@ -269,6 +275,29 @@ int main(int argc, char *argv[])
  *****************************************************************************/
 
 
+static void get_env_opts(Settings &args)
+{
+	// CLICOLOR is a de-facto standard option for colors <https://bixense.com/clicolors/>
+	// CLICOLOR != 0: ANSI colors are supported (auto-detection, this is the default)
+	// CLICOLOR == 0: ANSI colors are NOT supported
+	const char *clicolor = std::getenv(ENV_CLICOLOR);
+	if (clicolor && std::string(clicolor) == "0") {
+		args.set("color", "never");
+	}
+	// NO_COLOR only specifies that no color is allowed.
+	// Implemented according to <http://no-color.org/>
+	const char *no_color = std::getenv(ENV_NO_COLOR);
+	if (no_color && no_color[0]) {
+		args.set("color", "never");
+	}
+	// CLICOLOR_FORCE is another option, which should turn on colors "no matter what".
+	const char *clicolor_force = std::getenv(ENV_CLICOLOR_FORCE);
+	if (clicolor_force && std::string(clicolor_force) != "0") {
+		// should ALWAYS have colors, so we ignore tty (no "auto")
+		args.set("color", "always");
+	}
+}
+
 static bool get_cmdline_opts(int argc, char *argv[], Settings *cmd_args)
 {
 	set_allowed_options(&allowed_options);