This project has been created as part of the 42 curriculum by ebin-ahm.

ft_printf

---

Description

---

Purpose

To recode printf function from scratch, stylised as ft_printf in accordance to 42 standard without using the internal buffering system of the original printf, while supporting all mandatory format specifiers.

Brief Overview

printf is a key function in C that takes in a format string, prints and output a formatted string . printf reads a string, character by character, while interpreting % as format specifiers.

Each format specifier tells printf what type of argument to retrieve from the variadic argument list (using va_list, va_start, va_arg, and va_end) and how to convert that value into text.

Specifier	Description
%c	Print a single character
%s	Print a string
%p	Print a pointer address (0x + hex)
%d / %i	Print a signed integer
%u	Print an unsigned integer
%x	Print a lowercase hexadecimal number
%X	Print an uppercase hexadecimal number
%%	Print a literal % character

The final output is written to standard output, and printf returns the total number of characters printed.

Structure of ft_printf

Makefile – builds the libftprintf.a library

ft_printf.h – contains function prototypes and required headers

ft_printf.c – parses the format string and handles variadic arguments

print_*.c files – handle printing for each format specifierr

---

Instructions

Compilation

To compile the library, run:

make

To remove object files:

make clean

To remove object files AND the library:

make fclean

To rebuild everything:

make re

How to Compile Your Program (main.c) With ft_printf()

cc -Wall -Wextra -Werror main.c libftprintf.a -o program
./program

---

printf structure & algorithm

Structure

ft_printf/ ├── Makefile ├── README.md ├── ft_printf.h ├── ft_printf.c ├── print_char.c ├── print_string.c ├── print_int.c ├── print_unsigned.c ├── print_hex.c ├── print_pointer.c └── print_percent.c

Each print_.c file implements the logic for a specific format specifier, keeping the design modular and easy to maintain.*

Algorithm

1. ft_printf iterates through the format string character by character while managing a va_list.

2. Regular characters are written directly to standard output using write() and counted.

3. When a % is encountered, the next character is treated as a format specifier and dispatched to the appropriate handler using va_arg.

4. Each handler prints its value (handling special cases such as NULL) and returns the number of characters printed, which is added to the total count.

5. After processing the entire format string, va_end is called and ft_printf returns the total number of characters written.

Resources

Classic References

• man pages for standard library functions
• 42 Norminette rules
• 42 ft_printf PDF version 12.0

AI-Assisted Learning

AI (ChatGPT) was used for:

1. Clarifying concepts such as pointers, memory operations, and linked list operations
2. Explaining algorithms, edge cases, and debugging

All code was manually written and verified by ebin-ahm.