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

libft

Description

libft is a C library that reimplements essential standard library functions from libc, along with additional utility functions. The library is designed to deepen understanding of fundamental C programming concepts including memory management, string manipulation, and data structures.

The project is divided into two parts:

• Mandatory: Core libc function reimplementations plus common helpers not found in the standard library
• Bonus: Singly linked-list manipulation functions

The compiled library is a static archive (libft.a) that can be linked into other projects together with its header libft.h.

Instructions

Compilation

Compile the mandatory part:

make

Compile both mandatory and bonus parts:

make bonus

Clean object files:

make clean

Remove object files and the library:

make fclean

Rebuild from scratch:

make re

Usage

Include the header in your C files:

#include "libft.h"

Compile your project and link against libft:

gcc -o your_program your_program.c -L. -lft

Library Overview

Character checks (<ctype.h> reimplementations)

Function	Purpose
ft_isalpha	Test for an alphabetic character
ft_isdigit	Test for a decimal digit
ft_isalnum	Test for an alphanumeric character
ft_isascii	Test whether a value fits in the 7-bit ASCII range
ft_isprint	Test for a printable character, including space
ft_toupper	Convert a lowercase letter to uppercase
ft_tolower	Convert an uppercase letter to lowercase

Memory

Function	Purpose
ft_memset	Fill a memory block with a constant byte
ft_bzero	Zero out a memory block
ft_memcpy	Copy bytes between non-overlapping blocks
ft_memmove	Copy bytes between blocks that may overlap
ft_memchr	Locate the first occurrence of a byte in a block
ft_memcmp	Compare two memory blocks byte by byte
ft_calloc	Allocate and zero an array

Strings (<string.h> reimplementations)

Function	Purpose
ft_strlen	Return the length of a string
ft_strlcpy	Size-bounded string copy
ft_strlcat	Size-bounded string concatenation
ft_strchr	Locate the first occurrence of a character
ft_strrchr	Locate the last occurrence of a character
ft_strncmp	Compare up to n bytes of two strings
ft_strnstr	Locate a substring within the first n bytes
ft_strdup	Allocate a copy of a string

String helpers (allocating)

Function	Purpose
ft_substr	Allocate a substring of a string
ft_strjoin	Allocate the concatenation of two strings
ft_strtrim	Allocate a copy with leading/trailing characters removed
ft_split	Split a string on a delimiter into a NULL-terminated array
ft_strmapi	Allocate a string built by applying a function to each index/character
ft_striteri	Apply a function in place to each index/character

Conversions

Function	Purpose
ft_atoi	Convert the initial portion of a string to an int
ft_itoa	Allocate the string representation of an int

File-descriptor output

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

Bonus — linked lists

Operates on t_list nodes (void *content + struct s_list *next).

Function	Purpose
ft_lstnew	Allocate a new node holding the given content
ft_lstadd_front	Insert a node at the head of the list
ft_lstadd_back	Append a node at the tail of the list
ft_lstsize	Count the nodes in a list
ft_lstlast	Return the last node of a list
ft_lstdelone	Free one node's content and the node
ft_lstclear	Free and delete every node of a list
ft_lstiter	Apply a function to each node's content
ft_lstmap	Build a new list by applying a function to each node's content

Resources

References

• C standard library documentation (Linux/BSD man pages)
• 42 curriculum materials
• POSIX.1 specifications for the corresponding libc functions

AI usage

AI was not used for any of the function implementations, the header, or the Makefile — those were written independently from the function specifications and standard library behavior. It was used only to review and tighten the wording and structure of this README.