make 'forceexit' more fprintf-like, better error message when ioctl fails.

nethogs.cpp

@@ -10,6 +10,7 @@
 #include <signal.h>
 #include <string>
 #include <string.h>
+#include <stdarg.h>
 
 #include <netinet/ip.h>
 #include <netinet/ip6.h>
@@ -200,21 +201,16 @@ void quit_cb (int i)
 	exit(0);
 }
 
-void forceExit(const char *msg)
-{
-	forceExit (msg, NULL);
-}
-
-void forceExit(const char *msg, const char* msg2)
+void forceExit(const char *msg, ...)
 {
 	if ((!tracemode)&&(!DEBUG)){
 		exit_ui();
 	}
-	std::cerr << msg;
-	if (msg2 != NULL)
-	{
-		std::cerr << msg2;
-	}
+
+	va_list argp;
+	va_start(argp, msg);
+	vfprintf(stderr, msg, argp);
+	va_end(argp);
 	std::cerr << std::endl;
 
     exit(0);

nethogs.h

@@ -47,8 +47,7 @@
 
 #define PROGNAME_WIDTH 27
 
-void forceExit(const char *msg);
-void forceExit(const char *msg, const char* msg2);
+void forceExit(const char *msg, ...);
 
 class local_addr {
 public:

packet.cpp

@@ -43,7 +43,7 @@ void getLocal (const char *device, bool tracemode)
 	}
 	strcpy(iFreq.ifr_name, device);
 	if(ioctl(sock, SIOCGIFADDR, &iFreq)<0){
-		forceExit("ioctl failed while establishing local IP for selected device ", device);
+		forceExit("ioctl failed while establishing local IP for selected device %s. You may specify the device on the command line.", device);
 	}
 	saddr=(struct sockaddr_in*)&iFreq.ifr_addr;
 	local_addrs = new local_addr (saddr->sin_addr.s_addr, local_addrs);