Libft

A reusable static C library developed during the 42 curriculum. It implements common character, string, memory, conversion, and file-descriptor helpers, with additional linked-list routines, formatted output, and buffered line reading.

The library is used as a Git submodule by projects including Minitalk, Push Swap, and Wireframe Model.

Build

Requirements: a C compiler, Make, and the ar archive tool. Some functions use POSIX file descriptors and read()/write(), so a Unix-like environment is expected.

git clone https://github.com/civanaban2/libft.git
cd libft
make

The output is libft.a. The default compiler is cc with -Wall -Wextra -Werror.

To add linked-list functions to an archive containing the core functions, run these commands in order:

make
make bonus

make bonus archives only the bonus objects; on a clean checkout it does not first build the core archive. Run both targets as shown if you need both sets.

Link into an application

Create example.c in the library root:

#include "libft.h"

int main(void)
{
    char *message;

    message = ft_strjoin("Hello, ", "libft!");
    if (message == NULL)
        return 1;
    ft_putendl_fd(message, 1);
    free(message);
    return 0;
}

cc -Wall -Wextra -Werror -I. example.c -L. -lft -o example
./example
# Hello, libft!

Place -lft after the application object/source files when linking. Public function declarations and the t_list structure are in libft.h.

Function groups

Group	Functions
Character classification	ft_isalpha, ft_isdigit, ft_isalnum, ft_isascii, ft_isprint
Case conversion	ft_toupper, ft_tolower
Memory	ft_memset, ft_bzero, ft_memcpy, ft_memmove, ft_memchr, ft_memcmp, ft_calloc
String length/copy	ft_strlen, ft_strlcpy, ft_strlcat, ft_strdup
String search/compare	ft_strchr, ft_strrchr, ft_strncmp, ft_strnstr
Allocated string operations	ft_substr, ft_strjoin, ft_strtrim, ft_split, ft_itoa
String callbacks	ft_strmapi, ft_striteri
Numeric conversion	ft_atoi, ft_atol
File-descriptor output	ft_putchar_fd, ft_putstr_fd, ft_putendl_fd, ft_putnbr_fd
Extensions	ft_printf, get_next_line

Bonus linked-list functions:

ft_lstnew        ft_lstadd_front  ft_lstadd_back
ft_lstsize       ft_lstlast       ft_lstdelone
ft_lstclear      ft_lstiter       ft_lstmap

ft_printf supports characters, strings, pointers, signed decimal, unsigned decimal, lowercase/uppercase hexadecimal, and literal percent conversions: %c, %s, %p, %d, %i, %u, %x, %X, and %%. It is a limited implementation, without general field width, precision, or length modifiers.

get_next_line(int fd) returns one allocated line per call, including its newline when present. BUFFER_SIZE defaults to 1024. This bundled version uses a single persistent buffer; it is not the separate multi-descriptor bonus implementation from the Get Next Line repository.

Memory ownership and behavior

• Free allocated string results when they are no longer needed.
• For ft_split, free every returned token and then the pointer array.
• get_next_line results belong to the caller; NULL represents EOF or failure.
• Linked-list content cleanup is controlled by the caller's del callback.
• In the current implementation, ft_lstmap clears its input list after mapping. Do not assume a non-destructive mapping contract or reuse pointers into that input list afterward.

These are educational implementations. Do not assume complete ISO C/POSIX conformance or identical error behavior to the standard library. Allocation failure paths, allocation-size overflow, conversion overflow, and callback ownership need review before use with untrusted inputs. Not every function accepts null pointers, even though a few explicitly handle them.

Make targets

Target	Action
make	Build the core static archive
make bonus	Archive the linked-list objects
make clean	Remove core and bonus object files
make fclean	Also remove libft.a
make re	Clean and rebuild core functions
make rebonus	Clean and rebuild core and bonus functions

Run cleanup/rebuild targets without parallel -j execution. The existing Makefile does not track header dependencies; after changing libft.h, perform a clean rebuild.

Submodule consumers

A parent project records an exact libft commit, rather than automatically using the newest main. Use the parent's submodule initialization instructions and retain its recorded revision unless intentionally updating the dependency.

After a history rewrite, parent repositories must update their recorded submodule commit to a revision available on the current libft branch. This repository uses a single main branch.