libft

What is this?

libft is a hands-on C learning project from 42 School. The idea is to re-create some of C standard library functions from scratch in order to understand the foundations of C programming. Every function here is my own implementation, meant to be reused across future C projects in my learning journey.

This isn't designed as bulletproof, production-grade code. Instead, by working through all the tough bits (and making my share of mistakes), I now trust my C fundamentals. Plus, I’ve got a toolbox I understand inside and out.

What’s inside?

• String functions: ft_strlen, ft_strcpy, ft_strdup, ft_strncmp, ft_strcat, ft_strchr, ft_strrchr, ft_strnstr, etc.
• Memory functions: ft_memset, ft_memcpy, ft_memmove, ft_memcmp, ft_calloc, etc.
• Character checks/conversions: ft_isalpha, ft_isdigit, ft_isprint, ft_isalnum, ft_isascii, ft_toupper, ft_tolower, ...
• Numeric/string conversion: ft_atoi (ASCII to int), ft_itoa (int to ASCII), ...
• Split/join functions: ft_split (split a string by delimiter), ft_strjoin (concatenate strings), ...
• List utilities: Simple linked list operations, like ft_lstnew, ft_lstadd_back, ft_lstdelone, etc.
• Output helpers: ft_putchar_fd, ft_putstr_fd, ft_putnbr_fd, ...
• Other handy stuff: Small helper functions to round out the basics.

What did I learn?

• How to track down and fix segmentation faults and pointer mistakes.
• What pointers actually do (and what happens if you get them wrong).
• How memory allocation works in order to manage memory propperly, avoiding both leaks and overflows.
• The value of modularizing code and organizing functions logically.
• How propper organization can make a codebase far more readable, maintainable and debuggable.

How do you use this library?

You'll need any C compiler and make installed. Just run the following inside the libft/ directory:

make

Resulting files

• The static library archive will be located at: libft/lib/libft.a
• The header for all declarations will be found at: libft/include/libft.h

Example with gcc

Suppose you have a file named main.c:

#include "libft.h"

int main(void) {
    char *s = "Hello World!";
    int len = ft_strlen(s);

    ft_putnbr_fd(len, 1);
    ft_putchar_fd('\n', 1);
    return 0;
}

Compile with:

gcc -Ilibft/include main.c -Llibft/lib -lft

Or using Makefile, you might set it up like:

NAME = main
SRCS = main.c
LIBFTDIR = libft
LIB = $(LIBFTDIR)/lib/libft.a
INC = -I$(LIBFTDIR)/include

$(NAME): $(SRCS)
	make -C $(LIBFTDIR)
	gcc $(SRCS) $(INC) -L$(LIBFTDIR)/lib -lft -o $(NAME)

clean:
	make -C $(LIBFTDIR) clean
	rm -f $(NAME)

fclean: clean
	make -C $(LIBFTDIR) fclean

re: fclean $(NAME)

And that's it.