Libft

A comprehensive C standard library reimplementation

Overview • Features • Getting Started • API Reference • Usage • License

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Overview

Libft is a portable, lightweight C library that reimplements essential standard library functions from scratch. Originally developed as a foundational project at 42, it has evolved into a fully-featured utility library suitable for any C project.

The library provides:

• String manipulation — safe, null-checked string operations
• Memory management — allocation, copying, and comparison utilities
• Linked lists — generic singly-linked list implementation
• Formatted output — feature-complete printf family with extensions
• File I/O — file reading and line-by-line parsing (get_next_line)
• Debug utilities — binary and hex memory inspection

Features

• Zero external dependencies (only libc)
• Strict compilation with -Wall -Wextra -Werror
• Incremental builds with automatic dependency tracking
• Modular architecture — include only what you need
• Extensively tested against edge cases

Strings

Function	Description
ft_strlen	String length
ft_strchr	Find char in string
ft_strrchr	Find char from end
ft_strncmp	Compare n bytes
ft_strlcpy	Safe string copy
ft_strlcat	Safe string concatenate
ft_strdup	Duplicate string
ft_substr	Extract substring
ft_strjoin	Concatenate two strings
ft_strtrim	Trim characters from ends
ft_strnstr	Find substring
ft_split	Split string by delimiter
ft_strmapi	Map function over string
ft_striteri	Iterate with function

Number Conversion

Function	Description
ft_atoi	String to integer
ft_itoa	Integer to string

Getting Started

Prerequisites

• A C compiler (gcc or clang)
• GNU Make

Installation

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

This produces libft.a, a static library ready to link.

Quick Start

#include "libft.h"

int main(void)
{
    char *str = ft_strdup("Hello, Libft!");
    ft_printf("%s\n", str);
    free(str);
    return 0;
}

Compile with:

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

Using as a Git Submodule

git submodule add https://github.com/darrenkuro/libft.git libft
git submodule update --init --recursive

Then in your Makefile:

LIBFT_DIR = libft
LIBFT = $(LIBFT_DIR)/libft.a

$(LIBFT):
	$(MAKE) -C $(LIBFT_DIR)

$(NAME): $(OBJS) $(LIBFT)
	$(CC) $(OBJS) -L$(LIBFT_DIR) -lft -o $@

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API Reference

Character Functions

Function	Description
ft_isalpha(c)	Check if character is alphabetic
ft_isdigit(c)	Check if character is a digit
ft_isalnum(c)	Check if character is alphanumeric
ft_isascii(c)	Check if character is ASCII
ft_isprint(c)	Check if character is printable
ft_toupper(c)	Convert to uppercase
ft_tolower(c)	Convert to lowercase

String Functions

Function	Description
ft_strlen(s)	Get string length
ft_strchr(s, c)	Find first occurrence of character
ft_strrchr(s, c)	Find last occurrence of character
ft_strncmp(s1, s2, n)	Compare strings up to n bytes
ft_strnstr(big, lit, n)	Find substring within length limit
ft_strlcpy(dst, src, n)	Safe string copy
ft_strlcat(dst, src, n)	Safe string concatenation
ft_strdup(s)	Duplicate string
ft_substr(s, start, len)	Extract substring
ft_strjoin(s1, s2)	Concatenate two strings
ft_strtrim(s, set)	Trim characters from both ends
ft_split(s, c)	Split string by delimiter
ft_strmapi(s, f)	Apply function to each character (new string)
ft_striteri(s, f)	Apply function to each character (in place)

Memory Functions

Function	Description
ft_memset(b, c, n)	Fill memory with byte
ft_bzero(s, n)	Zero-fill memory
ft_memcpy(dst, src, n)	Copy memory (non-overlapping)
ft_memmove(dst, src, n)	Copy memory (overlap-safe)
ft_memchr(s, c, n)	Find byte in memory
ft_memcmp(s1, s2, n)	Compare memory blocks
ft_calloc(count, size)	Allocate and zero-initialize

Conversion Functions

Function	Description
ft_atoi(s)	String to integer
ft_itoa(n)	Integer to string

Output Functions

Function	Description
ft_putchar_fd(c, fd)	Write character to file descriptor
ft_putstr_fd(s, fd)	Write string to file descriptor
ft_putendl_fd(s, fd)	Write string with newline
ft_putnbr_fd(n, fd)	Write number to file descriptor

Printf Family

Function	Description
ft_printf(fmt, ...)	Formatted output to stdout
ft_dprintf(fd, fmt, ...)	Formatted output to file descriptor
ft_snprintf(buf, n, fmt, ...)	Formatted output to sized buffer
ft_vsnprintf(buf, n, fmt, args)	snprintf with va_list
ft_asprintf(out, fmt, ...)	Formatted output to allocated string
ft_vasprintf(out, fmt, args)	asprintf with va_list

Supported specifiers: c s p d i u x X %

Extensions: %m (memory hex dump), %b (binary)

Supported flags: - 0 + (space) # . *

Linked List Functions

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

Function	Description
ft_lstnew(content)	Create new node
ft_lstsize(lst)	Count nodes
ft_lstlast(lst)	Get last node
ft_lstadd_front(lst, node)	Add node at beginning
ft_lstadd_back(lst, node)	Add node at end
ft_lstdelone(node, del)	Delete single node
ft_lstclear(lst, del)	Delete all nodes
ft_lstiter(lst, f)	Apply function to each node
ft_lstmap(lst, f, del)	Create new list by mapping

File I/O Functions

Function	Description
get_next_line(fd)	Read next line from file descriptor
ft_read_file(path)	Read entire file into string

String Array Functions

Function	Description
ft_strarrlen(arr)	Get length of NULL-terminated string array
ft_strarrcpy(arr)	Deep copy string array

Debug Functions

Function	Description
ft_printb(ptr, len)	Print memory as binary
ft_printh(ptr, len)	Print memory as hexadecimal
ft_printc(ptr, len)	Print memory as characters

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Usage

Example: String Processing

#include "libft.h"
#include <stdlib.h>

int main(void)
{
    char **words = ft_split("hello,world,libft", ',');

    for (int i = 0; words[i]; i++)
    {
        ft_printf("Word %d: %s\n", i, words[i]);
        free(words[i]);
    }
    free(words);
    return 0;
}

Example: Linked List

#include "libft.h"
#include <stdlib.h>

void print_content(void *content)
{
    ft_printf("%s\n", (char *)content);
}

int main(void)
{
    t_list *head = ft_lstnew(ft_strdup("first"));
    ft_lstadd_back(&head, ft_lstnew(ft_strdup("second")));
    ft_lstadd_back(&head, ft_lstnew(ft_strdup("third")));

    ft_lstiter(head, print_content);
    ft_lstclear(&head, free);
    return 0;
}

Example: Reading Files

#include "libft.h"
#include <stdlib.h>

int main(void)
{
    char *line;
    int fd = open("file.txt", O_RDONLY);

    while ((line = get_next_line(fd)) != NULL)
    {
        ft_printf("%s", line);
        free(line);
    }
    close(fd);
    return 0;
}

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Project Structure

libft/
├── include/
│   ├── libft.h          # Main header
│   ├── ft_printf.h      # Printf declarations
│   └── ft_list.h        # Linked list types
├── src/
│   ├── ft_char.c        # Character functions
│   ├── ft_str.c         # String functions
│   ├── ft_mem.c         # Memory functions
│   ├── ft_num.c         # Number conversions
│   ├── ft_io.c          # I/O and get_next_line
│   ├── ft_lst.c         # Linked list
│   ├── ft_strarr.c      # String arrays
│   ├── ft_printf.c      # Printf implementation
│   └── ft_debug.c       # Debug utilities
├── Makefile
├── LICENSE
└── README.md

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Build Options

make          # Build libft.a
make clean    # Remove object files
make fclean   # Remove all build artifacts
make re       # Full rebuild
make DEBUG=1  # Build with debug symbols (-g)

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License

This project is licensed under the MIT License. See LICENSE for details.

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_{Built with care at 42}