This project has been created as part of the 42 curriculum by fcamasa.

Libft — 42 C Library

I could say that this project is like our own tool box that helps us to make all future projects possible by using all the tools that we have created inside this project, our own tools kit.

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Table of Contents

• Description
• Functions
  • Libc Functions
  • Additional Functions
  • Linked List — Bonus
• Getting Started
• Resources
• Author

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Description

Libft is a from-scratch reimplementation of key functions from the C standard library (libc), extended with additional utilities for string manipulation, memory management, and linked lists.

The primary goal is to understand how memory management (malloc, free), pointers, and data structures work at a low level in C — without relying on native functions. This forces manual handling of buffer overflows, memory leaks, and undefined behaviors. The library serves as the code foundation for all subsequent 42 cursus projects such as get_next_line, ft_printf, and minishell.

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Functions

1. Libc Functions

Reimplementations of standard tools from the C library.

Character checks — <ctype.h>

Function	Description
ft_isalpha	Returns true if the character is alphabetic
ft_isdigit	Returns true if the character is a digit
ft_isalnum	Returns true if the character is alphanumeric
ft_isascii	Returns true if the character is in the ASCII table
ft_isprint	Returns true if the character is printable
ft_toupper	Converts a lowercase letter to uppercase
ft_tolower	Converts an uppercase letter to lowercase

Memory management — <string.h> / <stdlib.h>

Function	Description
ft_memset	Fills a memory block with a specific byte
ft_bzero	Sets a memory block to zero
ft_memcpy	Copies a memory region from source to destination
ft_memmove	Same as memcpy but handles overlapping regions safely
ft_memchr	Searches for a byte within a memory block
ft_memcmp	Compares two memory blocks byte by byte
ft_calloc	Allocates zero-initialized memory dynamically

String manipulation — <string.h>

Function	Description
ft_strlen	Returns the length of a string
ft_strlcpy	Copies a string with guaranteed null-termination
ft_strlcat	Concatenates two strings with guaranteed null-termination
ft_strchr	Finds the first occurrence of a character in a string
ft_strrchr	Finds the last occurrence of a character in a string
ft_strncmp	Compares two strings up to n characters
ft_strnstr	Locates a substring within a string, up to n characters
ft_strdup	Duplicates a string into a newly allocated memory region
ft_atoi	Converts a numeric string to a signed integer

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2. Additional Functions

Custom utilities not found in the standard library.

Function	Description
ft_substr	Extracts a substring from a string at a given index and length
ft_strjoin	Concatenates two strings into a new allocated string
ft_strtrim	Removes a set of characters from both ends of a string
ft_split	Splits a string into an array of strings using a delimiter
ft_itoa	Converts an integer to its string representation
ft_strmapi	Applies a function to each character of a string (returns new string)
ft_striteri	Applies a function to each character of a string (in place)
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 a newline to a file descriptor
ft_putnbr_fd	Writes an integer to a file descriptor

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3. Linked List — Bonus

Functions for managing the t_list dynamic data structure.

Function	Description
ft_lstnew	Creates a new list node
ft_lstadd_front	Inserts a node at the beginning of the list
ft_lstadd_back	Inserts a node at the end of the list
ft_lstsize	Returns the number of nodes in the list
ft_lstlast	Returns the last node of the list
ft_lstdelone	Frees a single node using a custom delete function
ft_lstclear	Frees the entire list using a custom delete function
ft_lstiter	Applies a function to the content of each node
ft_lstmap	Applies a function to each node and returns a new list

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Getting Started

1. Clone and compile

git clone https://github.com/fcamasa/libft.git
cd libft
make

This produces libft.a, the static library archive.

2. Use in your project

Copy libft.a and libft.h into your project, then include the header and link at compile time:

#include "libft.h"

gcc main.c -L. -lft -I. -o my_program

3. Makefile rules

Rule	Description
make / make all	Compiles source files and builds libft.a
make clean	Removes intermediate .o files
make fclean	Removes .o files and libft.a
make re	Full rebuild from scratch

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Resources

Resource	Description
Linux Man Pages	Official reference for standard libc function behavior
GNU C Library Docs	Deep technical reference for core library design
GeeksforGeeks — C	Guides on pointers, strings, and dynamic memory
Francinette	Popular 42 tester for Libft — catches edge cases before evaluation

AI Usage

AI tools were used in two specific areas of this project:

• Understanding functions — Used to clarify the expected behavior of certain standard libc functions, cross-referencing man pages with practical explanations to ensure correct reimplementation.
• Debugging — Used to help identify the root cause of unexpected behaviors, memory errors, and edge cases during development.
• Visual edtiting - Used for visual editing of my Makefile content ,

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Author

fcamasa — 42 student