42-Libft

Your very first own C library.

A foundational project at 42 School, aimed at re-coding essential C standard library functions and learning how to build your own reusable library.

📘 Introduction

The Libft project is about creating your own C library that re-implements many of the functions you will use throughout your future projects. It helps you understand the inner workings of common C functions, memory handling, and linked lists — building a strong foundation for low-level programming.

Someone lost in C pointers 😵‍💫

libft/
├── .github/workflows
│           └── run-test.yaml
├── Makefile
├── includes/
│   └── libft.h
├── src/
│   ├── Mandatory/
│   │   ├── *.c
│   └── Bonus/
│       ├── *.c
└── README.md

🧾 Common Instructions

• Your project must follow 42’s Norm (norminette).

• Your functions must not crash (no segfaults, double frees, or memory leaks).

• All dynamically allocated memory must be properly freed.

• You must include a Makefile with at least the rules:

  NAME, all, clean, fclean, re

• The bonus part should be compiled with:

  make bonus

• You are encouraged to create and use test programs for your own validation.

When the norminette says OK ✅ 😂

🧱 Mandatory Part

Requirement	Details
Library Name	libft.a
Files to turn in	*.c, libft.h, Makefile
Compiler	cc
Flags	-Wall -Wextra -Werror
No global variables	✅ Required
Create archive with	ar (not libtool)

🧩 Part 1 – Libc Functions

Re-code the following C standard library functions (without using restrict):

  isalpha   isdigit   isalnum   isascii   isprint
  strlen    memset    bzero     memcpy    memmove
  strlcpy   strlcat   toupper   tolower   strchr
  strrchr   strncmp   memchr    memcmp    strnstr
  atoi

And using malloc:

  calloc    strdup

malloc never returns NULL… right? 😅

🧰 Part 2 – Additional Functions

Functions that are not in libc or have modified behavior:

Function	Description
ft_substr	Returns a substring from a string.
ft_strjoin	Concatenates two strings.
ft_strtrim	Trims characters from the beginning and end of a string.
ft_split	Splits a string using a delimiter.
ft_itoa	Converts an integer to a string.
ft_strmapi	Applies a function to each character of a string (creates a new string).
ft_striteri	Applies a function to each character of a string (in-place).
ft_putchar_fd	Outputs a character to a file descriptor.
ft_putstr_fd	Outputs a string to a file descriptor.
ft_putendl_fd	Outputs a string followed by a newline.
ft_putnbr_fd	Outputs an integer to a file descriptor.

🧩 Bonus Part

Once you’ve completed the mandatory part, you can implement linked list functions.

🧱 Struct Definition

typedef struct s_list
{
    void            *content;
    struct s_list   *next;
} t_list;

🔗 Bonus Functions

Function	Description
ft_lstnew	Creates a new list node.
ft_lstadd_front	Adds a node at the beginning.
ft_lstsize	Returns the number of nodes.
ft_lstlast	Returns the last node.
ft_lstadd_back	Adds a node at the end.
ft_lstdelone	Frees a single node.
ft_lstclear	Frees an entire list.
ft_lstiter	Iterates over a list and applies a function.
ft_lstmap	Creates a new list by applying a function to each node.

To compile with the bonus part:

make bonus

Linked list chaos 🪢😂

🧪 Compilation Examples

# Compile the library
make

# Compile the bonus functions
make bonus

# Clean object files
make clean

# Remove binaries and library
make fclean

# Recompile from scratch
make re

# Build and run test program
make test

Makefile says Done compiling 😁👍

🧰 Test the Norminette or Build via GitHub Actions

If you want to check your code’s Norminette or Build automatically through GitHub:

1. Go to your repository on GitHub.
2. Click on the "Actions" tab.
3. Find the workflow named “Check the Norminette or Build of the code”.
4. Click “Run workflow”.
5. In the dropdown, select the type → Choose the type of test?.
6. Click “Run workflow” again.

GitHub Actions will automatically test your code against the Norminette or Build rules and display the result in the Actions panel ✅.

Waiting for CI to pass ⏳🤞

🧠 Tips

• Test your functions one by one before adding them to the library.
• Keep helper (static) functions internal — don’t expose them in libft.h.
• Check memory leaks.
• Expand your Libft as you progress — it’s your foundation for future 42 projects.

🏁 Final Goal

By the end of this project, you will:

• Understand how the C standard library works internally
• Have a custom reusable C library for all future projects
• Master memory management, string manipulation, and linked list operations

💬 Author

Made with ❤️ as part of the 42 School Curriculum

“Understanding the foundation of C is the first step toward mastering programming.”

Thanks for reading 🙌