ft_printf

A lightweight, 42-style reimplementation of the C standard library's printf, written in C and built as a static library.

This project provides a drop-in function ft_printf with a subset of standard printf features commonly required in the 42 curriculum.

• Language: C
• Build system: Makefile

Features

• Function signature:

  int ft_printf(const char *format, ...);

• Returns the number of characters printed.
• Writes to standard output (file descriptor 1).
• Supported conversion specifiers:
  • %c — character
  • %s — string
  • %p — pointer (hexadecimal with 0x prefix)
  • %d, %i — signed decimal integer
  • %u — unsigned decimal integer
  • %x — unsigned hexadecimal (lowercase)
  • %X — unsigned hexadecimal (uppercase)
  • %% — literal percent sign

Getting Started

Prerequisites

• A C toolchain (e.g., gcc or clang)
• make

Build

From the project root:

make

Common Makefile targets:

• make — build the library
• make clean — remove object files
• make fclean — remove objects and the library
• make re — rebuild from scratch

Using ft_printf in your project

1. Include the header in your source:

   #include "ft_printf.h"

2. Compile and link against the static library. Example:

   gcc -Wall -Wextra -Werror -I./include -c main.c
   gcc -o app main.o -L. -lftprintf
   # or simply
   gcc -Wall -Wextra -Werror main.c ./libftprintf.a -I./include

Minimal example

#include "ft_printf.h"

int main(void)
{
    int printed = ft_printf("Hello, %s! Number: %d Hex: %x %%\n", "world", 42, 0x2A);
    ft_printf("Characters printed above: %d\n", printed);
    return 0;
}

Build:

gcc -Wall -Wextra -Werror main.c ./libftprintf.a -I./include -o demo
./demo

Behavior Notes

• The return value accumulates the count of characters successfully written.
• Pointer values are printed with a 0x prefix followed by lowercase hexadecimal digits.

Testing

Quick comparison test:

int a = ft_printf("Mine => %d %x %p %%\n", 42, 42, &a);
int b = printf   ("Sys  => %d %x %p %%\n", 42, 42, &a);
printf("ft_printf count: %d | printf count: %d\n", a, b);

Compile:

gcc -Wall -Wextra -Werror test.c ./libftprintf.a -I./include -o test
./test

Development Guidelines

• Compile with -Wall -Wextra -Werror.
• Keep functions small and focused on a single conversion responsibility.
• Consider adding internal helper functions for hexadecimal and pointer formatting.