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

ft_printf: Because ft_putnbr() and ft_putstr() Aren't Enough 🖨️

Welcome to ft_printf, a custom structural implementation of the standard printf function found in libc. This project marks the transition from using static output utilities to engineering dynamic formatting pipelines using C's native variadic argument interfaces.

🚀 Project Overview

The core objective of this project is to replicate the format-parsing string mechanics of printf without relying on standard buffer-pooling frameworks. The function evaluates characters sequentially, routes specifiers through an internal parsing core, dynamically handles base conversions via custom memory allocation subroutines, tracks the total printed-byte length via an internal counter, and interfaces safely with low-level kernel write streams.

💡 Scope Limitation: This implementation satisfies the mandatory criteria. It does not process field minimum widths or complex attribute formatting flags (-, 0, ., #, +, or spaces).

🛠️ Tech Stack & Standards

• Language: C (Strictly compliant with The Norm standard)
• Compilation Tooling: cc utilizing diagnostic flags -Wall -Wextra -Werror
• Native Context Requirements: Integrated tracking types and system resources:
  • <stdarg.h> — For variadic argument management (va_list, va_start, va_arg, va_end)
  • <unistd.h> — For system stream access (write)
  • <stdlib.h> — For isolated byte allocations (malloc, free)
  • <stdint.h> — For macro evaluation limits (SIZE_MAX)

📂 Project Structure

📂 ft_printf/
├── 📄 ft_printf.h          # Central Header (Macros, Types, System Inclusions)
├── 📄 ft_printf.c          # Primary Entry Point & Character Iteration Loop
├── 📄 ft_putchar_pf.c      # Safe Single Character Output Subroutine
├── 📄 ft_putstr_pf.c       # String Output Handler with Native Edge Safety
├── 📄 ft_putnbr_pf.c       # Base-10 Signed Integer Translation Core
├── 📄 ft_putuint_pf.c      # Base-10 Unsigned Integer Format Handler
├── 📄 ft_puthex_pf.c       # Low-Level Base-16 Hexadecimal Engine
├── 📄 ft_putptr_pf.c       # Unsigned Address Conversion & Pointer Printer
├── 📄 ft_aux_pf.c          # Explicit Memory Allocations & Parsing Utils
├── 📄 Makefile             # Multi-File Archiver Lifecycle Controller
└── 📄 README.md            # Structural Overview & Documentation Matrix

The function handles the following conversions

Format	Behaviour
%c	Prints a single character
%s	Prints a string (as defined by the common C convention)
%p	The void * pointer argument has to be printed in hexadecimal format
%d	Prints a decimal (base 10) number
%i	Prints an integer in base 10
%u	Prints an unsigned decimal (base 10) number
%x	Prints a number in hexadecimal (base 16) lowercase format
%X	Prints a number in hexadecimal (base 16) uppercase format
%%	Prints a percent sign

Variadic functions

Printf handles variable number of arguments. It is necessary because we don't know in advance how many arguments is the user going to ask to print. The ... stands for the variable arguments in the function prototype. Then you need to initiate it as if it was a normal variable va_list va;. Before starting to use it in the function you need to start it with va_start(va, str); and end it at the end it of the function with va_end(va);.

Resources

• Gitbook ft_printf guide
• Makefile tutorial
• C notes, debugging
• man printf
• man va_list
• man va_arg

Description of AI used for this project

For this project I used AI for the compilation, because I was unsure how am I supposed to compile a complex project with multiple files, and create one executable file. I learned it with the help of my peers and asking AI to explain too.

Justification of use of libraries

In my ft_printf.h file I am including the following libraries:

• stdarg.h
  • It is necessary for the use of the variadic functions.
• unistd.h
  • It is necessary to use the function write.
• stdlib.h
  • It is necessary, because I am using malloc.
• stdint.h
  • It is necessary, because I am using SIZE_MAX.

Instructions

Action	Command
You can compile it with	make
Delete object files	make clean
Delete all objects	make fclean
Delete and recompile from scratch	make re

You can use this main to test

• First create the main.c file.

• Now run make to create the object files.

• Then create the executable file with cc -Wall -Wextra -Werror main.c libftprintf.a.

• Finally you can simply execute the program with ./a.out.

#include "ft_printf.h"
#include <stdio.h>

int	main(void)
{
	ft_printf("Hello %s! Number: %d\n", "42", 42);
	ft_printf("Hex: %x | Ptr: %p\n", 255, &main);
	return (0);
}