shrpx: Color severity level in terminal

Color severity level if stderr refers to a terminal.

src/shrpx.cc

@@ -369,6 +369,7 @@ void fill_default_config()
   mod_config()->gid = 0;
   mod_config()->backend_ipv4 = false;
   mod_config()->backend_ipv6 = false;
+  mod_config()->tty = isatty(fileno(stderr));
 }
 } // namespace
 

src/shrpx_config.h

@@ -122,6 +122,8 @@ struct Config {
   char *cacert;
   bool backend_ipv4;
   bool backend_ipv6;
+  // true if stderr refers to a terminal.
+  bool tty;
 };
 
 const Config* get_config();

src/shrpx_log.cc

@@ -33,9 +33,20 @@
 
 namespace shrpx {
 
+namespace {
 const char *SEVERITY_STR[] = {
   "INFO", "WARN", "ERROR", "FATAL"
 };
+} // namespace
+
+namespace {
+const char *SEVERITY_COLOR[] = {
+  "\033[1;32m", // INFO
+  "\033[1;33m", // WARN
+  "\033[1;31m", // ERROR
+  "\033[1;35m", // FATAL
+};
+} // namespace
 
 int Log::severity_thres_ = WARNING;
 
@@ -80,12 +91,17 @@ Log::Log(int severity, const char *filename, int linenum)
 Log::~Log()
 {
   if(severity_ >= severity_thres_) {
-    fprintf(stderr, "[%s] %s\n       (%s, line %d)\n",
-            SEVERITY_STR[severity_], stream_.str().c_str(),
-            filename_, linenum_);
+    fprintf(stderr, "[%s%s%s] %s\n       %s(%s:%d)%s\n",
+            get_config()->tty ? SEVERITY_COLOR[severity_] : "",
+            SEVERITY_STR[severity_],
+            get_config()->tty ? "\033[0m" : "",
+            stream_.str().c_str(),
+            get_config()->tty ? "\033[1;30m" : "",
+            filename_, linenum_,
+            get_config()->tty ? "\033[0m" : "");
     fflush(stderr);
     if(get_config()->use_syslog) {
-      syslog(severity_to_syslog_level(severity_), "%s (%s, line %d)\n",
+      syslog(severity_to_syslog_level(severity_), "%s (%s:%d)\n",
              stream_.str().c_str(), filename_, linenum_);
     }
   }