Can someone please help me understand ,in simple language, What is a makefile ? what are its uses?
I tied various sources from the net but the have been unable to cope with the rich technical grammar .
Hello @piyukr,
A makefile is just an easy way to compile several source files at once, simply using the command-line command make.
I will try to provide you with an example:
Suppose you decided to write a program to calculate factorials of a number, and, furthermore, assume you wrote two distinct versions:
An iterative one, which you placed on the file iter.c and a recursive one, you placed on the file recurs.c;
Also, due to modularity and portability restrictions assume that you had to declare the prototype of the factorial function on a separate header file, called, fact.h;
To end, assume that you have a fourth file, called main.c, that attempts to use one of the factorial functions defined on one of the files, recurs.c or iter.c;
So, we have:
- fact.h -> Header file that contains the factorial function declaration,
int factorial(int n); - iter.c -> C source code file that contains the code for the iterative definition of factorial function;
- recurs.c -> C source code file that contains the code for the recursive definition of factorial function;
- main.c -> C source code file that contains a simple usage of one of the above functions (that are defined on a separate file, this is usually how projects are deployed);
Now, to compile with command line the code for the iterative version, you could do:
gcc -o iterative iter.c main.c
which will produce you object files and an executable file called iterative (the .exe file goes with the name you pass to the -o flag), so, to run your program you can now do ./iterative and you’re done.
and the same for the recursive version…
This work because on this simple example, our function main.c is only “dependent” on one function definition and as a consequence on one header file…
However, assume you are working on a huge large scale project with say, some dozens of dependencies… Then, compiling everything by hand would be very time consuming… For such situations we can have a Makefile.
For the example I provided you, if I wanted to compile the iterative and recursive functions all at once, I could create a plain text file, name it Makefile, put it on the directory where all source folders/files are located and write something like this:
CFLAGS= -g -O2 -Wall -pedantic -ansi
OBJECTS1= main.o recurs.o
OBJECTS2= main.o iter.o
all:
make factorial-recurs
make factorial-iter
factorial-recurs : $(OBJECTS1)
gcc $(CFLAGS) -o factorial-recurs $(OBJECTS1)
factorial-iter : $(OBJECTS2)
gcc $(CFLAGS) -o factorial-iter $(OBJECTS2)
main.o: main.c fact.h
iter.o: iter.c fact.h
recurs.o: recurs.c fact.h
clean :
rm factorial-recurs
rm factorial-iter
rm *.o
run : make all
./factorial-iter
Like this, on a terminal you can simple type the command make all and all files would be compiled 
If you attempt to read the above “code” carefully you will see that the vast majority of its content is simply flag definitions to make the compilation command cleaner and shorter
I hope I could help,
Best regards,
Bruno
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Thanks a lot @kuruma .One question - Does the concept of makefiles apply for all languages or just C ?
A Makefile applies to basically every compiled language, and I guess you could do the same to a language like C,C++, Java or other…
A major exception to this “Makefile standard” is Google’s programming language Go, that has some features which allow for a compilation of several files at once without any conflicts and without the need for a Makefile…
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thank you