ft_printf

Reimplementation of a simplified version of the printf function for the 42 curriculum. This project provides a custom implementation capable of printing formatted output using variadic arguments, hexadecimal conversions, pointers, and basic numeric/string types.

Project developed at 42 Telefónica by Diego Valladares Ortega.

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ft_printf is a static C library that recreates part of the functionality of the standard C printf function. It handles formatted output parsing, type conversions, and printing to the standard output.

Supported format specifiers:

%c — print a character

%s — print a string

%p — print a pointer in hexadecimal format

%d / %i — print a signed decimal integer

%u — print an unsigned decimal integer

%x / %X — print a number in lowercase/uppercase hexadecimal

%% — print a literal percent sign

The goal is to understand formatted output internals, manage va_list, and implement type-safe printing without relying on libc's printf.

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📁 Project Structure

src/        # All ft_*.c files (implementations)
include/    # Public header: ft_printf.h
Makefile    # Builds the static library: libftprintf.a

🔧 Build Instructions

Clone the repository:

git clone https://github.com/<TU_USUARIO>/libftprintf.git
cd libftprintf

Build the library:

make

This will generate:

./libftprintf.a

Clean object files:

make clean

Remove objects + library:

make fclean

Recompile everything:

make re

🧪 Testing (Optional)

42 does not require official tests for this project, but you can create simple tests such as:

#include "ft_printf.h"

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

Compile and run:

cc tests/main.c -L. -lftprintf -Iinclude -o test_printf
./test_printf

Compare results with the original printf to validate correctness.

📚 Implemented Functionalities Core printing functions

• ft_printf

• Parsing of format strings

• Handling of va_list

Conversion handlers

• Character output

• String output

• Signed/unsigned integer printing

• Hexadecimal conversion (lowercase & uppercase)

• Pointer address formatting

Utility functions

• Low-level printing helpers (write)

• Counting printed characters

• Integer-to-hex and integer-to-unsigned conversions

🧠 What I Learned

• How printf processes format strings internally

• Using stdarg.h and va_list for variadic functions

• Converting integers to different bases (decimal, hex)

• Manual implementation of printing logic without libc formatting

• Clean separation of modules in a small C library

• Building static archives with ar

• Writing structured, norm-compliant C code

📄 License

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