Add '--quiet' comand line option to suppress some output

NEWS

@@ -27,6 +27,7 @@ ncmpcpp-0.8 (????-??-??)
 * Seek immediately after invoking appropriate action once.
 * Added support for locating current song in playlist editor.
 * Disable autocenter mode while searching and filtering.
+* Added '--quiet' comand line argument that supresses messages shown at startup.
 
 ncmpcpp-0.7.7 (2016-10-31)
 * Fixed compilation on 32bit platforms.

doc/ncmpcpp.1

@@ -33,6 +33,9 @@ Specify the startup screen (<name> may be: help, playlist, browser, search_engin
 .B \-S, \-\-slave-screen <name>
 Specify the startup slave screen (<name> may be: help, playlist, browser, search_engine, media_library, playlist_editor, tag_editor, outputs, visualizer, clock)
 .TP
+.B \-q, \-\-quiet
+Suppress logs and excess output
+.TP
 .B \-?, \-\-help
 Display help.
 .TP

src/configuration.cpp

@@ -24,6 +24,7 @@
 #include <boost/program_options.hpp>
 #include <iomanip>
 #include <iostream>
+#include <fstream>
 
 #include "bindings.h"
 #include "configuration.h"
@@ -88,6 +89,7 @@ bool configure(int argc, char **argv)
 		("slave-screen,S", po::value<std::string>()->value_name("SCREEN"), "specify the startup slave screen")
 		("help,?", "show help message")
 		("version,v", "display version information")
+		("quiet,q", "suppress logs and excess output")
 	;
 
 	po::variables_map vm;
@@ -95,6 +97,14 @@ bool configure(int argc, char **argv)
 	{
 		po::store(po::parse_command_line(argc, argv, options), vm);
 
+		// suppress messages from std::clog
+		if (vm.count("quiet"))
+		{
+			std::ofstream null_stream;
+			null_stream.open("/dev/null");
+			std::clog.rdbuf(null_stream.rdbuf());
+		}
+
 		if (vm.count("help"))
 		{
 			cout << "Usage: " << argv[0] << " [options]...\n" << options << "\n";

src/ncmpcpp.cpp

@@ -54,6 +54,7 @@ namespace {
 
 std::ofstream errorlog;
 std::streambuf *cerr_buffer;
+std::streambuf *clog_buffer;
 
 volatile bool run_resize_screen = false;
 	
@@ -69,8 +70,9 @@ void sighandler(int sig)
 
 void do_at_exit()
 {
-	// restore old cerr buffer
+	// restore old cerr & clog buffers
 	std::cerr.rdbuf(cerr_buffer);
+	std::clog.rdbuf(clog_buffer);
 	errorlog.close();
 	Mpd.Disconnect();
 	NC::destroyScreen();
@@ -92,6 +94,9 @@ int main(int argc, char **argv)
 	std::setlocale(LC_ALL, "");
 	std::locale::global(Charset::internalLocale());
 
+	// clog might be overriden in configure, so preserve the original buffer.
+	clog_buffer = std::clog.rdbuf();
+
 	if (!configure(argc, argv))
 		return 0;