Don't use color escape codes if terminal doesn't support them in ansicolor_sink

include/spdlog/details/os.h

@@ -12,6 +12,7 @@
 #include <string>
 #include <chrono>
 #include <thread>
+#include <algorithm>
 #include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
@@ -401,6 +402,32 @@ inline int pid()
 
 }
 
+
+// Detrmine if the terminal supports colors
+// Source: https://github.com/agauniyal/rang/
+bool is_color_terminal()
+{
+#ifdef _WIN32
+	return true;
+#else		
+	static constexpr const char* Terms[] = {
+		"ansi", "color", "console", "cygwin", "gnome", "konsole", "kterm",
+		"linux", "msys", "putty", "rxvt", "screen", "vt100", "xterm"
+	};
+
+	const char *env_p = std::getenv("TERM");
+	if (env_p == nullptr) {
+		return false;
+	}
+
+	static const bool result = std::any_of(
+		std::begin(Terms), std::end(Terms), [&](const char* term) {
+		return std::strstr(env_p, term) != nullptr;
+	});
+#endif 
+}
+
+
 } //os
 } //details
 } //spdlog

include/spdlog/sinks/ansicolor_sink.h

@@ -7,6 +7,7 @@
 
 #include <spdlog/sinks/base_sink.h>
 #include <spdlog/common.h>
+#include <spdlog/details/os.h>
 
 #include <string>
 #include <map>
@@ -66,12 +67,14 @@ public:
 
 
 		protected:
+			bool is_color_terminal_;
 			sink_ptr sink_;
 			std::map<level::level_enum, std::string> colors_;
 		};
 
 		inline ansicolor_sink::ansicolor_sink(sink_ptr wrapped_sink): sink_(wrapped_sink)
 		{
+			is_color_terminal_ = details::os::is_color_terminal();
 			colors_[level::trace] = cyan;
 			colors_[level::debug] = cyan;
 			colors_[level::info] = bold;
@@ -83,7 +86,9 @@ inline ansicolor_sink::ansicolor_sink(sink_ptr wrapped_sink) : sink_(wrapped_sin
 
 		inline void ansicolor_sink::log(const details::log_msg& msg)
 		{
-    // Wrap the originally formatted message in color codes
+			// Wrap the originally formatted message in color codes.
+			// If color is not supported in the terminal, log as is instead.
+			if (is_color_terminal_) {
 				const std::string& prefix = colors_[msg.level];
 				const std::string& s = msg.formatted.str();
 				const std::string& suffix = reset;
@@ -95,6 +100,10 @@ inline void ansicolor_sink::log(const details::log_msg& msg)
 				m.formatted << prefix << s << suffix;
 				sink_->log(m);
 			}
+			else {
+				sink_->log(msg);
+			}
+		}
 
 		inline void ansicolor_sink::flush()
 		{