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ft_printf

A custom implementation of the printf function - 42 School Project

Overview

ft_printf is a 42 School project that involves recoding the standard C library function printf(). This project teaches about variadic functions, parsing, and how one of the most used functions in C actually works under the hood.

Description

The goal is to create a library containing a function ft_printf() that mimics the behavior of the original printf function from the C standard library. The function handles multiple format specifiers and returns the number of characters printed.

Features

Supported Conversions

The ft_printf function handles the following format specifiers:

  • %c - Print a single character
  • %s - Print a string
  • %p - Print a pointer address in hexadecimal format
  • %d - Print a signed decimal integer
  • %i - Print a signed integer
  • %u - Print an unsigned decimal integer
  • %x - Print a number in lowercase hexadecimal format
  • %X - Print a number in uppercase hexadecimal format
  • %% - Print a percent sign

Key Functions

  • ft_printf() - Main function that formats and prints output
  • ft_exec_flag() - Parses and executes format specifiers
  • ft_putchar() - Outputs a single character
  • ft_putstr() - Outputs a string
  • ft_putnbr() - Outputs a signed integer
  • ft_putunbr() - Outputs an unsigned integer
  • ft_print_in_hexa_min() - Outputs lowercase hexadecimal
  • ft_print_in_hexa_max() - Outputs uppercase hexadecimal
  • ft_print_void_p() - Outputs pointer address

Installation & Compilation

Requirements

  • GCC compiler
  • Make

Compilation

To compile the library:

make

This will create the static library libftprintf.a.

Cleaning

Remove object files:

make clean

Remove object files and the library:

make fclean

Recompile everything:

make re

Usage

  1. Compile the library:
make
  1. Include the header in your C file:
#include "ft_printf.h"
  1. Compile your program with the library:
gcc your_program.c libftprintf.a -o your_program

Example Usage

#include "ft_printf.h"

int main(void)
{
    int num = 42;
    char *str = "Hello, World!";
    void *ptr = #

    // Print different types
    ft_printf("Character: %c\n", 'A');
    ft_printf("String: %s\n", str);
    ft_printf("Pointer: %p\n", ptr);
    ft_printf("Decimal: %d\n", num);
    ft_printf("Integer: %i\n", -42);
    ft_printf("Unsigned: %u\n", 42);
    ft_printf("Hex (lower): %x\n", 255);
    ft_printf("Hex (upper): %X\n", 255);
    ft_printf("Percent: %%\n");

    // Returns number of characters printed
    int ret = ft_printf("Test: %d\n", 123);
    ft_printf("Characters printed: %d\n", ret);

    return (0);
}

Output

Character: A
String: Hello, World!
Pointer: 0x7ffd5c4a3b8c
Decimal: 42
Integer: -42
Unsigned: 42
Hex (lower): ff
Hex (upper): FF
Percent: %
Test: 123
Characters printed: 9

Project Structure

ft_printf/
├── Makefile              # Build configuration
├── include/
│   └── ft_printf.h       # Header file with function prototypes
├── src/
│   ├── ft_printf.c       # Main ft_printf implementation
│   ├── prints_one.c      # Helper functions for printing (part 1)
│   └── prints_two.c      # Helper functions for printing (part 2)
└── README.md             # This file

Technical Details

  • Language: C
  • Compiler: GCC
  • Compilation Flags: -Wall -Wextra -Werror
  • Library Type: Static library (.a)
  • Key Concepts:
    • Variadic functions (va_list, va_start, va_arg, va_end)
    • Format string parsing
    • Type conversions
    • Hexadecimal representation
    • Return value management
  • Norm: 42 School coding standard (Norminette)

Implementation Details

Variadic Functions

The project uses the <stdarg.h> library to handle variable argument lists:

  • va_list - Type for argument list
  • va_start() - Initialize argument list
  • va_arg() - Retrieve next argument
  • va_end() - Clean up argument list

Return Value

Like the original printf, ft_printf returns the total number of characters printed to the standard output.

Modular Design

The implementation is split across multiple files for better organization:

  • Core printf logic in ft_printf.c
  • Print helper functions in prints_one.c and prints_two.c
  • Function prototypes in ft_printf.h

About 42 School

This project is part of the 42 School curriculum, focusing on understanding variadic functions and reimplementing standard library functions.

Author

bmetehri - 42 Student

Project completed: January 2023