Simple Hello world c programm and Makefile to start with Shared library in linux

Goal : To create a Make file to generate an executable using makefile in Ubuntu.
Requirements : Ubuntu, Knowledge of c programming.

First we will create a simple hello world c program.

Creating the source code for Hello World Program:

Contents of main.c

    #include
    int main()
    {
        printf("Hello world!");
    }

Compiling the source file using gcc

gcc main.c

This will generate a executable file as a.out.

1.b Generating a executable file with a given name

gcc main.c -o hello

1.c Modularising the print function

Modularising is good as they can be reused, archived as library, and for many more reasons

#include
void print_hello();

void print_hello()
{
printf("Hello world!");
}
int main()
{
print_hello();
}

1.d Creating seperate files for modules:
Its good to have releatives modules in a sepearate files

Content of main.c

int main()
{
print_hello();
}

Content of hello_func.c

#include
void print_hello()
{
printf("Hello world!");
}

Compiling the files

gcc hello_func.c main.c -o hello.out

1.d Creating header files

Every c file will have some header files included.

Content of main.c

#include "hello.h"
int main()
{
print_hello();
}

Content of hello_func.c

#include "hello.h"
void print_hello()
{
printf("Hello world!");
}

Content of hello.h

#include
void print_hello(void);

1.e Organizing the files

Its good to put up files in a organized manner.
So we put our modules, main and header files into source, test and include dirctory respectively as bellow.
And build directory to do the building.
.
├── build
├── include
│ └── hello.h
├── src
│ └── hello_func.c
└── test
└── hello.c

Compiling

cd build
gcc -I ../include/ ../src/hello_func.c ../test/hello.c -o hello.out

This will generate a hello.out in build directory

Now, we have very few files and its easy to manually use gcc to compile the code. But when the code grows,
Its difficult to handle build manually. So, now, we can create a makefile to build the code

2 Creating Makefile

we will put the same command used to build previously, but with little modifications.
I will say little enhancements, like bellow

Contents of Makefile

hello : ../include/hello.h ../src/hello_func.c ../test/hello.c
gcc -I ../include/ ../src/hello_func.c ../test/hello.c -o hello.out

hello : This is the Rule name
What ever following after the ‘:’ are the dependencies to be checked for.
Means, presence of these files will be checked before running the rule

Next line, starts with TAB. This defines actually what has to be run

Now, we can build the code using makefile by running the command ‘make’

3 Enhancing the Makefile

Now, we can take our makefile to the next step. Enhancements.
Still our code is very simple. We just have evry few files, so we can write the names manually.
What if the number of files is getting increased? We should make the Makefile easy to manage.

Contents of Makefile

PROJECT_NAME = hello
COMPILER = gcc

INCLUDE_DIR = ../include
TEST_DIR = ../test
SRC_DIR = ../src
EXECUTABLE_NAME = hello.out

SRC_FILES = ${SRC_DIR}/hello_func.c
TEST_FILES = ${TEST_DIR}/hello.c
INCLUDE_FILES = ${INCLUDE_DIR}/hello.h

${EXECUTABLE_NAME} : ${INCLUDE_FILES} ${SRC_FILES} ${TEST_FILES}
${COMPILER} -I ${INCLUDE_DIR} ${SRC_FILES} ${TEST_FILES} -o ${EXECUTABLE_NAME}

We are aliasing the names in more readable forms by assigning it to some variables or defines.

Now we can build using make command

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