outlab9

Problem1/Makefile

+.PHONY: all peer server
+all: peer server
+peer: peer.cpp
+	g++ peer.cpp -o peer
+server: server.o
+	g++ server.o -o server
+server.o: server.cpp peerinfo.hpp
+	g++ -c server.cpp
+	
+clean:
+	rm -rf *.o peer server

Problem1/README.txt

+
+peer.cpp: -	It is a menu driven program for peers which can publish the files to central server which
+	 	it wants to share to other peers & and it can search for files through central server get
+	 	that file from respective peer.
+	 	
+	 	IMP FUNCTIONS
+	 	startPServer() - It will start the server for peer in background to serve incoming request
+	 	of fellow peers
+	 	connToServer() - It will establish a connection with central server
+	 	displayMenu()  - It is used to display Menu for intraction
+	 	
+server.cpp: -	It is a program for central server which will establish a server for all the peers to connect
+		and fetch iformation about others.
+		
+		IMP FUNCTIONS
+		startServer() - It is used to start and initialise the server
+		acceptPeer()  - Accepts incoming peers request & stores its information 		 
+		
+peerinfo.hpp: -	It conatins a user defined class which stores all the necessary detials of peer who has 
+		established connectiom with server  
+	

Problem1/peer.cpp

+#include <stdio.h>
+#include <iostream>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <string.h>
+#include <string>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <fcntl.h>
+
+#define S_PORT 4500 											// Fixed port no. for SERVER
+#define BUFFER_SIZE 1024
+
+using namespace std;
+
+int startPServer(int pport, int &psoc);							// To start peers background server
+int connToServer(int &psocket, string serIP, int port);			// Establish connection with diffferent server
+int checkNdie(int status);										// Check for return values of varous function
+int displayMenu();
+int mySend(int sSoc, string &input);
+char buffer[BUFFER_SIZE];										// Buffer to store sent & recieved data
+
+int main(int argc, char const *argv[])
+{
+	int stat;													// Temp variable used to store return value of functions
+	int peersocket;												// Socket in which peers server is listening
+	int p2sSocket;												// Socket for communication with central server
+	int fileDes;												//	Descriptor for file
+	string file_name;
+	string op;
+
+	if( argc != 4)
+	{
+		cout<<"Run as: ./peer <Server Port> <Server IP> <Peer Port>\n";
+		return 1;
+	}
+	
+	startPServer(atoi(argv[3]), peersocket);
+
+	cout<<"Connecting to Central server...\n";
+	connToServer(p2sSocket, argv[2], atoi(argv[1]));					// Connects to central server
+	snprintf(buffer, BUFFER_SIZE, "%s", argv[3]);					// Sends peer's server port no. to central server  
+	send(p2sSocket, buffer, BUFFER_SIZE, 0);
+
+	int process = fork();
+		if( process > 0)
+		{	
+			do
+			{
+				displayMenu();
+				mySend(p2sSocket, op);
+
+					if( !strncmp(op.c_str(), "1", 1) )
+					{	
+						cout<<"Publish File : ";
+						mySend(p2sSocket, file_name);						// Publishes the file names to server
+						perror("Publish");
+					}	
+					else if( !strncmp(op.c_str(), "2", 1) )
+					{	
+						cout<<"Search File : ";
+						mySend(p2sSocket, file_name);
+
+						recv(p2sSocket, buffer, BUFFER_SIZE, 0);
+							if( strncmp(buffer, "NF", 2) )
+							{
+								string p2pIP = string(buffer);
+								cout<<"File is at: "<<p2pIP;
+								recv(p2sSocket, buffer, BUFFER_SIZE, 0);
+								string p2pPORT = string(buffer);
+								cout<<"::"<<p2pPORT<<"\n";
+
+								int p2pSocket;
+								cout<<"Connecting to peer : "<<p2pIP<<":"<<p2pPORT<<"\n";
+								connToServer(p2pSocket, p2pIP, atoi(p2pPORT.c_str()));		// Connects to other peer for download
+								cout<<"Connection Established...\n";
+
+								snprintf(buffer, BUFFER_SIZE, "%s", file_name.c_str());
+								send(p2pSocket, buffer, BUFFER_SIZE, 0);
+
+								snprintf(buffer, BUFFER_SIZE, "p2p-files/%s", file_name.c_str());
+								fileDes = open(buffer, O_RDWR | O_CREAT | O_APPEND );		// Open the file to write
+								perror("File open");
+
+								int Bsize;
+								int fsize=0;
+
+								cout<<"Downloading "<<file_name<<" ...\n";
+									while( (Bsize = read(p2pSocket, buffer, BUFFER_SIZE)) > 0 )			// Read from peer & write in file
+									{
+										fsize += Bsize;
+										//perror("Read");
+										write(fileDes, buffer, Bsize);
+									}
+
+								cout<<"Size = "<<fsize;
+								close(fileDes);
+								cout<<" Downloaded successfully "<<"\n";
+								close(p2pSocket);
+							}
+							else
+								cout<<"File not Found\n";
+					}	
+			}while( strncmp(op.c_str(), "3", 1) );
+		}
+		else
+		{
+			while(1)
+			{
+				struct sockaddr_in in_peer;								// For storing incoming peers address
+				socklen_t addrlen;
+				int in_peerFD;
+				char data[BUFFER_SIZE];
+
+				addrlen 	= 	sizeof(in_peer);
+				in_peerFD 	= 	accept(peersocket, (struct sockaddr *)&in_peer, &addrlen);
+
+				recv(in_peerFD, buffer, BUFFER_SIZE, 0);
+				snprintf(data, BUFFER_SIZE, "p2p-files/%s", buffer);
+				fileDes = open(data, O_RDONLY);							// Open File From Where to read
+				// perror("File open");
+				int Bsize;
+
+					while( (Bsize = read(fileDes, buffer, BUFFER_SIZE)) > 0 )
+					{
+						write(in_peerFD, buffer, Bsize);
+					}
+				close(fileDes);
+				close(in_peerFD);
+			}
+		}
+
+	close(peersocket);
+	close(p2sSocket);
+	return 0;
+}
+
+int startPServer(int pport, int &psoc)
+{
+	cout<<"Starting peer's server...\n";
+	struct sockaddr_in peer_server;
+	int stat	=	-1;			// Temp variable used to store return value of functions
+	
+	psoc = socket(AF_INET, SOCK_STREAM, 0);
+		/* Checks for succesfull creation of socket */ 
+	perror("Peer's Socket");
+	checkNdie(psoc);
+	
+	bzero(&peer_server, sizeof(peer_server));
+	peer_server.sin_family			=	AF_INET;
+	peer_server.sin_addr.s_addr 	=	htonl(INADDR_ANY);
+	peer_server.sin_port			=	htons(pport);
+
+	int optval = 1;
+    setsockopt(psoc, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));
+	stat	=	bind(psoc, (struct sockaddr *)&peer_server, sizeof(peer_server));	
+			/* Checks for binding of port & address */
+	perror("Bind");
+	checkNdie(stat);
+
+	stat	=	listen(psoc, 5);
+		/* Checks for listen error */
+	perror("Listen");
+	checkNdie(stat);
+	return 0;
+}
+
+int mySend(int sSoc, string &input)
+{
+	getline(cin, input);
+	snprintf(buffer, BUFFER_SIZE, "%s", input.c_str());
+	send(sSoc, buffer, BUFFER_SIZE, 0);
+	return 0;
+}
+
+int connToServer(int &psocket, string serIP, int port)
+{
+	int stat;
+	struct sockaddr_in cen_server;
+	char serip[50];
+	strcpy(serip, serIP.c_str());
+
+	psocket = socket(AF_INET, SOCK_STREAM, 0);
+	/* Checks for succesfull creation of socket */ 
+	perror("Socket");
+	checkNdie(psocket);
+
+	cen_server.sin_family		=	AF_INET;
+	cen_server.sin_addr.s_addr 	=	inet_addr(serip);
+	cen_server.sin_port			=	htons(port);
+
+	stat	=	connect(psocket, (struct sockaddr *)&cen_server, sizeof(cen_server));
+	/* Checks For successfull connection */
+	perror("Connect");
+	checkNdie(stat);
+}
+
+int displayMenu()
+{
+	cout<<"\n******Peer Main Menu******";
+	cout<<"\n\t1. Publish";
+	cout<<"\n\t2. Search & Fetch";
+	cout<<"\n\t3. Exit";
+	cout<<"\nSelect an option : ";
+	return 0;
+}
+
+int checkNdie(int status)
+{
+	if( status < 0 )
+		exit(1);
+
+	return 0;
+}
\ No newline at end of file

Problem1/peerinfo.hpp

+#include <stdio.h>
+#include <iostream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+class peerInfo
+{
+	private:
+		int socID;										// Socket in which peer is communicating with server
+		int port;										// Port in which peer's server is running
+		string IP;										// IP address of Peer
+		vector<string> files;							// List of File peers have
+
+	public:
+		peerInfo(int socketFD, string ip, int p)
+		{
+			socID	=	socketFD;
+			IP 		=	ip;
+			port 	=	p;
+		}
+
+		string getIP(){return IP;}
+
+		int getPort(){return port;}
+
+		int getsocID(){return socID;}
+
+		string getFile(int index){return files[index];}
+
+		void addFile(string file)									// Add new file to the list
+		{
+			files.push_back(file);
+		}
+
+		int searchFile(string sFile)								// Search for particular file in peers list of files
+		{
+			for (int i = 0; i < files.size(); ++i)
+				if ( files[i] == sFile )
+					return 1;
+
+			return 0;
+		}
+};
\ No newline at end of file

Problem1/server.cpp

+#include <stdio.h>
+#include <iostream>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <string.h>
+#include <string>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include "peerinfo.hpp"
+
+#define S_PORT 4500 						// Fixed port no. for SERVER
+#define BUFFER_SIZE 1024
+
+using namespace std;
+
+int startServer(int &serverSocket, int sPort);			// Function used to Initialise and start the server
+int acceptPeer(int soc);					// Accept new connection and returns FD for that client
+int checkNdie(int status);					// Check for return values of varous function 
+vector<peerInfo> peers;						// Saves the Informations of all peers which are connected
+char buffer[BUFFER_SIZE];
+char data[BUFFER_SIZE];
+
+int main(int argc, char const *argv[])
+{
+	fd_set masterFDS;
+	fd_set readFDS;
+
+	int serverSocket=0;
+	int maxFD;
+	int stat;								// Temp variable used to store return value of functions
+
+	if( argc != 2)
+	{
+		cout<<"Run as: ./server <Server Port>\n";
+		return 1;
+	}
+
+	startServer(serverSocket, atoi(argv[1]));
+	cout<<"Server Socket : "<<serverSocket<<"\n";
+
+	FD_ZERO(&masterFDS);
+	FD_ZERO(&readFDS);
+	FD_SET(serverSocket,&masterFDS);
+	maxFD	=	serverSocket;
+
+		while(1)
+		{
+			fflush(stdout);
+			readFDS	=	masterFDS;
+			stat 	=	select(maxFD+1, &readFDS, NULL, NULL, NULL);
+			checkNdie(stat);
+
+				for (int i = 0; i <= maxFD; ++i)				// Itterate through every fd to check activity
+				{
+					if ( FD_ISSET(i, &readFDS) )
+					{
+						if ( i == serverSocket)					// For new connection if activity is in server's socket
+						{
+							int peerFD	=	acceptPeer(serverSocket);		// Accept new Peer connection  
+							if( peerFD > 0)											// only if valid FD is returned
+							{
+								FD_SET(peerFD, &masterFDS);
+									if ( peerFD > maxFD )
+									{
+										maxFD	=	peerFD;
+									}
+							}
+						}
+						else									// Handles incoming data from peers
+						{
+							recv(i, data, BUFFER_SIZE, 0);
+
+							if( !strncmp(data, "1", 1) )				// IF peer want to publish, add file in peer's info
+							{
+								recv(i, buffer, BUFFER_SIZE, 0);
+									for (int j = 0; j < peers.size(); j++)
+									{
+										if ( peers[j].getsocID() == i)
+										{
+											peers[j].addFile(buffer);
+										}
+									}
+							}
+							else if( !strncmp(data, "2", 1) )				// IF peer wants to search for a file
+							{
+								recv(i, buffer, BUFFER_SIZE, 0);
+								int found = 0;
+									for (int j = 0; j < peers.size(); j++)
+									{
+										if( peers[j].searchFile( string(buffer) ))
+										{
+											found = 1;
+											snprintf(buffer, BUFFER_SIZE, "%s", peers[j].getIP().c_str());
+											send(i, buffer, BUFFER_SIZE, 0);
+											snprintf(buffer, BUFFER_SIZE, "%d", peers[j].getPort());
+											send(i, buffer, BUFFER_SIZE, 0);
+											break;
+										}
+									}	
+									if ( !found )
+									{
+										snprintf(buffer, BUFFER_SIZE, "NF");
+										send(i, buffer, BUFFER_SIZE, 0);
+									}
+							}
+							else if( !strncmp(data, "3", 1) )				// Show all files of that user
+							{
+									for (int j = 0; j < peers.size(); j++)
+									{
+										if ( peers[j].getsocID() == i)
+										{
+											cout<<"Peer Disconnected : "<<peers[j].getIP()<<"::"<<peers[j].getPort();
+											cout<<" socket : "<<peers[j].getsocID()<<"\n";
+											peers.erase( peers.begin()+j );
+											close(i);
+											FD_CLR(i, &masterFDS);
+										}
+									}	
+							}							
+							// else if( !strncmp(data, "0", 1) )				// Show all files of that user
+							// {
+							// 		for (int j = 0; j < peers.size(); j++)
+							// 		{
+							// 			if ( peers[j].getsocID() == i)
+							// 			{
+							// 				cout<<"Files of "<<peers[j].getIP()<<"::"<<peers[j].getPort()<<"\n";
+							// 				peers[j].showFiles();
+							// 			}
+							// 		}	
+							// }
+						}
+					}
+				}
+		}
+
+	close(serverSocket);
+
+	return 0;
+}
+
+int startServer(int &serverSocket, int sPort)
+{
+	int stat			=	-1;			// Temp variable used to store return value of functions
+	int serverPort		=	sPort;
+	struct sockaddr_in cen_server;
+	int i 	=	0;
+
+	serverSocket = socket(AF_INET, SOCK_STREAM, 0);
+		/* Checks for succesfull creation of socket */ 
+	perror("Socket");
+	checkNdie(serverSocket);
+	
+	bzero(&cen_server, sizeof(cen_server));
+	cen_server.sin_family		=	AF_INET;
+	cen_server.sin_addr.s_addr 	=	htonl(INADDR_ANY);
+	cen_server.sin_port			=	htons(serverPort);
+
+	int optval = 1;
+    setsockopt(serverSocket, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));
+	stat	=	bind(serverSocket, (struct sockaddr *)&cen_server, sizeof(cen_server));	
+			/* Checks for binding of port & address */
+	perror("Bind");
+	checkNdie(stat);
+
+	stat	=	listen(serverSocket, 5);
+		/* Checks for listen error */
+	perror("Listen");
+	checkNdie(stat);
+	return 0;
+}
+
+int acceptPeer(int soc)
+{
+	struct sockaddr_in peer;
+	socklen_t addrlen;
+	int peerFD;
+
+	addrlen	=	sizeof(peer);
+	peerFD	=	accept(soc, (struct sockaddr *)&peer, &addrlen);
+		if( peerFD == -1 )
+			perror("Accept");
+		else
+		{
+			recv(peerFD, buffer, BUFFER_SIZE, 0);				// Recieves port no. from peer in which it is working
+								
+			/* Add peer's info in vector of all peers */
+			peers.push_back(peerInfo(peerFD, inet_ntoa(peer.sin_addr), atoi(buffer)));
+			cout<<"New peer connected : "<<inet_ntoa(peer.sin_addr)<<"::"<<buffer<<" socket : "<<peerFD<<"\n";
+		}
+
+	return peerFD;
+}
+
+int checkNdie(int status)
+{
+	if( status < 0 )
+		exit(1);
+
+	return 0;
+}
\ No newline at end of file

Problem2/Makefile

+CC=g++
+
+CFLAGS=-c -Wall
+
+all: hello
+
+hello: main.o factorial.o hello.o
+	$(CC) main.o factorial.o hello.o -o hello
+
+main.o: main.cpp
+	$(CC) $(CFLAGS) main.cpp
+
+factorial.o: factorial.cpp
+	$(CC) $(CFLAGS) factorial.cpp
+
+hello.o: hello.cpp
+	$(CC) $(CFLAGS) hello.cpp
+
+clean:
+	rm -rf *.o hello

Problem2/factorial.cpp

+#include "functions.h"
+
+int factorial(int n){
+    if(n!=1){
+	return(n * factorial(n-1));
+    }
+    else return 1;
+}

Problem2/functions.h

+void print_hello();
+int factorial(int n);

Problem2/hello.cpp

+#include <iostream>
+using namespace std;
+#include "functions.h"
+
+void print_hello(){
+   cout << "Hello World!";
+}

Problem2/main.cpp

+#include <iostream>
+using namespace std;
+#include "functions.h"
+
+int main(){
+    print_hello();
+    cout << endl;
+    cout << "The factorial of 5 is " << factorial(5) << endl;
+    return 0;
+}

Problem3a/Makefile

+OBJECTS=main.o hello.o factorial.o
+
+hello: $(OBJECTS)
+	$(CXX) $(OBJECTS) -o hello
+main.o: main.cpp functions.h
+	$(CXX) -c main.cpp
+hello.o: hello.cpp functions.h
+	$(CXX) -c hello.cpp
+factorial.o: $(FACTM)
+	$(CXX) -c factorial.cpp
+	
+clean:
+	rm -rf *.o hello

Problem3a/factorial.cpp

+#include "functions.h"
+
+int factorial(int n){
+    if(n!=1){
+	return(n * factorial(n-1));
+    }
+    else return 1;
+}

Problem3a/functions.h

+void print_hello();
+int factorial(int n);

Problem3a/hello.cpp

+#include <iostream>
+#include "functions.h"
+
+using namespace std;
+
+void print_hello(){
+   cout << "Hello World!";
+}

Problem3a/main.cpp

+#include <iostream>
+#include "functions.h"
+
+using namespace std;
+
+int main(){
+    print_hello();
+    cout << endl;
+    cout << "The factorial of 5 is " << factorial(5) << endl;
+    return 0;
+}

Problem3b/Makefile

+hellomake: hellomake.o hellofunc.o
+	gcc $^ -o $@
+hellomake.o: hellomake.c hellomake.h
+	gcc -c $<
+hellofunc.o: hellofunc.c hellomake.h
+	gcc -c $<
+	
+clean:
+	rm -rf *.o hellomake

Problem3b/hellofunc.c

+#include <stdio.h>
+#include "hellomake.h"
+
+void myPrintHelloMake(void) {
+
+  printf("Hello makefiles!\n");
+
+  return;
+}

Problem3b/hellomake.c

+#include "hellomake.h"
+
+int main() {
+  // call a function in another file
+  myPrintHelloMake();
+
+  return(0);
+}

Problem3b/hellomake.h

+/*
+example include file
+*/
+
+void myPrintHelloMake(void);
\ No newline at end of file

Problem4/Makefile

+SUBDIRS = mt_client mt_server
+SERVER= ./mt_server
+CLIENT= ./mt_client
+path = $(shell pwd)
+port = 8080 
+export path port 
+.PHONY: all clean run_server run_client
+
+all clean:
+	for dir in $(SUBDIRS); do\
+		$(MAKE) -C $$dir -f Makefile $@; \
+	done
+run_server:
+	
+	$(MAKE) -C $(SERVER) run
+run_client:
+	
+	$(MAKE) -C $(CLIENT) run
+# server:
+# 	$(MAKE) -C $(SERVER)
+# client:
+# 	$(MAKE) -C $(CLIENT)
+# clean: $(CLEAN_SERV) $(CLEAN_CL)
+# $(CLEAN_SERV):
+# 	$(MAKE) -C $(SERVER) clean
+# $(CLEAN_CL):
+# 	$(MAKE) -C $(CLIENT) clean
\ No newline at end of file

Problem4/Makefile.c

+CLPATH= ./mt_client/
+TLPATH= $(path)
+HDEP=cl_task.h cl_utils.h
+CFLAGS=-c -g -pthread -Wall
+OBJECT = build
+
+NUM_THREADS = 10
+HOST_NAME = localhost
+PATH_TO_EXEC = $(path)/client.out
+
+all: $(OBJECT) client
+$(OBJECT):
+	if [ ! -d ./$(OBJECT) ];then \
+		mkdir -p $(OBJECT);   \
+	fi
+client: $(TLPATH)/client.out
+
+$(TLPATH)/client.out: $(OBJECT)/mt_client.o $(OBJECT)/cl_task.o $(OBJECT)/cl_utils.o
+	$(CC) -pthread $^ -o $@
+$(OBJECT)/mt_client.o: mt_client.c $(HDEP)
+	$(CC) $(CFLAGS) $< -o $@
+$(OBJECT)/cl_task.o: cl_task.c $(HDEP)
+	$(CC) $(CFLAGS) $< -o $@
+$(OBJECT)/cl_utils.o: cl_utils.c cl_utils.h
+	$(CC) $(CFLAGS) $< -o $@
+	
+run:
+	$(PATH_TO_EXEC) $(HOST_NAME) $(port) $(NUM_THREADS)
+
+
+
+	
+clean:
+	@rm -r $(PATH_TO_EXEC) $(OBJECT)/*.o $(OBJECT)

Problem4/Makefile.s

+SERVPATH=./mt_server/
+TLPATH= $(path)
+HDEP=sv_task.h sv_utils.h
+CFLAGS=-c -g -pthread -Wextra
+OBJECT = build
+PATH_TO_EXEC = $(path)/server.out
+
+all: $(OBJECT) server
+$(OBJECT):
+	if [ ! -d ./$(OBJECT) ];then \
+		mkdir -p $(OBJECT);   \
+	fi
+
+server: $(TLPATH)/server.out
+$(TLPATH)/server.out: $(OBJECT)/mt_server.o $(OBJECT)/sv_task.o $(OBJECT)/sv_utils.o
+	$(CC) -pthread $^ -o $@
+$(OBJECT)/mt_server.o: mt_server.c $(HDEP)
+	$(CC) $(CFLAGS) $< -o $@
+$(OBJECT)/sv_task.o: sv_task.c $(HDEP)
+	$(CC) $(CFLAGS) $< -o $@
+$(OBJECT)/sv_utils.o: sv_utils.c sv_utils.h
+	$(CC) $(CFLAGS) $< -o $@
+	
+run:
+	$(PATH_TO_EXEC) $(port)
+clean:
+	@rm -rf $(OBJECT)/*.o $(PATH_TO_EXEC) $(OBJECT)

readme.txt

+CSE GitLab username: sanjnamohan
+Link to  GitLab repository: https://git.cse.iitb.ac.in/sanjnamohan/outLab9
+
+
+Contributions:
+Sanjna Mohan (20305R006): Problem4
+Manjusree M P (203059007): Problem3,Problem4
+Pooja Gayakwad (203050076): Problem1
+Snehlata Yadav (203050075): Problem2
+
+
+References:
+https://www.gnu.org/software/make/manual/make.pdf
+https://www.oreilly.com/library/view/managing-projects-with/0596006101/ch06.html
+https://www.tutorialspoint.com/makefile/makefile_features.htm
+https://www.cmcrossroads.com/article/making-directories-gnu-make
+https://www.gnu.org/software/make/manual/html_node/MAKE-Variable.html#MAKE-Variable
+https://www.linuxquestions.org/questions/programming-9/makefiles-and-subdirectories-794088/
+https://stackoverflow.com/questions/5178125/how-to-place-object-files-in-separate-subdirectory/27794283
+https://ftp.gnu.org/old-gnu/Manuals/gdb/html_node/gdb_16.html#:~:text=Compiling%20for%20debugging&text=This%20debugging%20information%20is%20stored,when%20you%20run%20the%20compiler.
+https://stackoverflow.com/questions/12697012/passing-variables-from-include-directive-to-sub-make
+https://stackoverflow.com/questions/28890634/how-to-get-a-shell-environment-variable-in-a-makefile
+https://tack.ch/gnu/make-3.82/make_43.html
+https://gist.github.com/linse/87f3b44d59a9d298309c
+http://lackof.org/taggart/hacking/make-example/
+https://www.cs.bu.edu/teaching/cpp/writing-makefiles/
+https://www.tutorialspoint.com/makefile/makefile_macros.htm
+https://stackoverflow.com/questions/3220277/what-do-the-makefile-symbols-and-mean
+https://stackoverflow.com/questions/5191436/creating-two-separate-executables-from-a-makefile-g
+https://www.tutorialspoint.com/makefile/index.htm
+
+