ft_printf

A custom implementation of printf developed as part of the 42 curriculum. ft_printf is a small formatted output library that reproduces the core behavior of printf with the conversions required by the subject.

It was a good way to build solid foundations in formatted output, function decomposition and variadic argument handling in C.

Features

• Reimplementation of a simplified printf
• Support for variadic arguments through stdarg.h
• Handling of the mandatory 42 format specifiers
• Static library build with make

Project structure

• ft_printf.h — header file with function prototypes
• ft_printf.c — main formatted output dispatcher
• ft_putchar.c — character output helper
• ft_putstr.c — string output helper
• ft_putnbr.c — signed integer output helper
• ft_puthex.c — hexadecimal output helper
• ft_putptr.c — pointer output helper
• Makefile — builds the libftprintf.a static library

Mandatory part

The mandatory part focuses on the conversions and helper functions needed to reproduce the expected printf behavior.

Main function

• ft_printf — parses the format string, reads variadic arguments, dispatches each conversion and returns the total number of printed characters

Supported conversions

• %c — prints a single character
• %s — prints a string
• %p — prints a pointer address in hexadecimal form
• %d — prints a signed decimal number
• %i — prints an integer in base 10
• %u — prints an unsigned decimal number
• %x — prints a hexadecimal number using lowercase letters
• %X — prints a hexadecimal number using uppercase letters
• %% — prints a literal percent sign

Helper functions

• ft_putchar — writes one character and returns the number of printed characters
• ft_putstr — writes a string and returns the number of printed characters
• ft_putnbr — writes a signed number and returns the printed length
• ft_puthex — writes a number in hexadecimal format and returns the printed length
• ft_putptr — writes a pointer value in hexadecimal format and returns the printed length

Build

Build the library:

make

Clean object files:

make clean

Remove object files and library:

make fclean

Rebuild everything:

make re

Learning outcomes

This project was my first real introduction to variadic functions and formatted output in C. It helped build solid foundations in:

• variadic argument handling with va_start, va_arg and va_end
• output formatting logic
• recursive or decomposed number printing
• hexadecimal conversion
• return value tracking
• modular code organization