libft

Custom implementation of the C standard library, built from scratch as part of the 42 Madrid curriculum.

This library serves as the foundation for all future C projects at 42 — no external functions allowed, everything reimplemented by hand.

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Project Structure

libft/
├── src/        # Mandatory functions
├── bonus/      # Linked list functions
├── includes/   # libft.h header
├── Makefile
└── README.md

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Functions

Character Checks & Conversions

Function	Description
ft_isalpha	Checks if character is alphabetic
ft_isdigit	Checks if character is a digit
ft_isalnum	Checks if character is alphanumeric
ft_isascii	Checks if character is ASCII
ft_isprint	Checks if character is printable
ft_toupper	Converts character to uppercase
ft_tolower	Converts character to lowercase

String Manipulation

Function	Description
ft_strlen	Returns the length of a string
ft_strchr	Locates a character in a string
ft_strrchr	Locates last occurrence of a character
ft_strncmp	Compares two strings up to n characters
ft_strnstr	Finds a substring in a string
ft_strdup	Duplicates a string
ft_substr	Extracts a substring
ft_strjoin	Concatenates two strings
ft_strtrim	Trims characters from both ends of a string
ft_split	Splits a string by a delimiter
ft_strmapi	Applies a function to each character
ft_striteri	Applies a function to each character with index
ft_strlcpy	Copies a string with size limit
ft_strlcat	Concatenates strings with size limit

Memory Management

Function	Description
ft_memset	Fills memory with a constant byte
ft_bzero	Zeroes out memory
ft_memcpy	Copies memory area
ft_memmove	Moves memory area safely
ft_memchr	Scans memory for a character
ft_memcmp	Compares two memory areas
ft_calloc	Allocates and zeroes memory

Conversions

Function	Description
ft_atoi	Converts a string to integer
ft_itoa	Converts an integer to string

File Descriptor Output

Function	Description
ft_putchar_fd	Writes a character to a file descriptor
ft_putstr_fd	Writes a string to a file descriptor
ft_putendl_fd	Writes a string followed by newline
ft_putnbr_fd	Writes an integer to a file descriptor

Linked List (Bonus)

Function	Description
ft_lstnew	Creates a new list node
ft_lstadd_front	Adds a node at the beginning
ft_lstadd_back	Adds a node at the end
ft_lstsize	Returns the number of nodes
ft_lstlast	Returns the last node
ft_lstdelone	Deletes a single node
ft_lstclear	Deletes all nodes
ft_lstiter	Applies a function to each node
ft_lstmap	Creates a new list from applying a function

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Usage

Compilation

make        # compile mandatory part
make bonus  # compile with linked list functions
make clean  # remove object files
make fclean # remove object files and libft.a
make re     # full rebuild

Using in your project

#include "libft.h"

gcc main.c -L. -lft -o program

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Author

Aitor Alonso Jusdado — 42 Madrid — LinkedIn