Linking multiple files in C - Mini Project: Build & Apply

Linking Multiple Files in C

📖 Scenario: You are creating a simple C program split into two files: one file will contain a function to greet a user, and the other will call this function and print the greeting.

🎯 Goal: Build a C program with two files: greet.c containing a function greet that returns a greeting string, and main.c that calls greet and prints the greeting.

📋 What You'll Learn

Create a function greet in greet.c that returns a greeting string.

Declare the function greet in a header file greet.h.

Include greet.h in main.c and call greet.

Print the greeting returned by greet in main.c.

Compile and link both files to produce the final executable.

💡 Why This Matters

🌍 Real World

Large C programs are split into multiple files to organize code better and allow multiple programmers to work together.

💼 Career

Understanding how to link multiple files is essential for software development in C, especially in systems programming and embedded development.

1

Create the greeting function in greet.c

Create a file called greet.c and write a function called greet that returns the string "Hello from greet.c!". Use const char* as the return type.

C

# Write the function greet in greet.c
// Your code here

Need a hint?

Define a function named greet that returns a constant string.

2

Create the header file greet.h

Create a header file called greet.h that declares the function greet with the signature const char* greet();. Add include guards to prevent multiple inclusion.

C

// Write the header file greet.h with include guards and declare greet
// Your code here

Need a hint?

Use #ifndef, #define, and #endif to create include guards.

3

Write main.c to call greet

Create a file called main.c. Include stdio.h and greet.h. In main, call greet and store the result in a variable called message. Then, print message using printf.

C

#include 
#include "greet.h"

int main() {
    // Call greet and print the message
    // Your code here
}

Need a hint?

Include the header greet.h and use printf to display the greeting.

4

Compile and run the program

Compile greet.c and main.c together using a command like gcc main.c greet.c -o greet_program. Then run the program with ./greet_program and print the output.

C

// Compile and run the program, then print the output below
// Your code here

Need a hint?

Use the terminal to compile and run. The output should be exactly Hello from greet.c!