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

FT_PRINTF

Project ft_printf / Milestone 1 / 42 Porto

Description

The goal of this project is to recreate the printf() function from the <stdio.h> library. This exercise teaches how to handle Variadic Arguments in C.

Supported conversions:

• %c: Prints a single character.
• %s: Prints a string (as defined by the common C convention).
• %p: The void * pointer argument is 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.

Logic & Algorithm

The main function ft_printf iterates through the format string.

1. It parses the string character by character.
2. If the character is not %, it writes it to the output and increments the count.
3. If it encounters a %, it checks the conversion type (e.g., s, d, x) using a dispatcher function.
4. It retrieves the corresponding argument using va_arg and formats it accordingly.
5. Finally, it returns the total number of characters printed.

Instructions

1. Compiling the library To compile the library libftprintf.a, run:

make

2. Using it in your code To use the function in your project, include the header and link the library: C

#include "ft_printf.h"
// ...
ft_printf("Hello 42 Porto %s", "World");

3. Testing If you don't have a test file, you can use the main.c example below. Compile it with your library: Bash

cc main.c libftprintf.a -o test_printf
./test_printf

Example main.c

You can save this code as main.c in your repository to test your function: C

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

int main(void)
{
    int     numero = 42;
    char    *string = "Teste"; 
    void    *ponteiro_nulo = NULL;
    int     resultado;
    int     resultad_0;

    // Testing ft_printf
    resultado = ft_printf("\n%%s:\t%s\n%%c:\t%c\n%%:\t%%\n%%d:\t%d\n%%i:\t%i\n%%x:\t%x\n%%X:\t%X\n%%u:\t%u\n-%%u:\t%u\n", "Laura", 'L', 27, -27, 45212, 45212, 289, -289);
    resultado += ft_printf("%%p:\t%p\n%%p:\t%p\n%%p:\t%p", &numero, string, ponteiro_nulo);
    resultado += ft_printf("\n-%%x:\t%x\n-%%X:\t%X\n", -42, -1289);

    // Testing original printf for comparison
    resultad_0 = printf("\n%%s:\t%s\n%%c:\t%c\n%%:\t%%\n%%d:\t%d\n%%i:\t%i\n%%x:\t%x\n%%X:\t%X\n%%u:\t%u\n-%%u:\t%u\n", "Laura", 'L', 27, -27, 45212, 45212, 289, -289);
    resultad_0 += printf("%%p:\t%p\n%%p:\t%p\n%%p:\t%p", &numero, string, ponteiro_nulo);
    resultad_0 += printf("\n-%%x:\t%x\n-%%X:\t%X\n", -42, -1289);

    printf("\n\nResultado ft_printf:\t%d\nResultado printf:\t%d\n\n", resultado, resultad_0);
    return (0);
}

Resources & AI Usage

References used:

Variadic Functions - 42 Guide

Microsoft Docs - va_arg

Book: "The C Programming Language" (K&R)

AI Usage: I utilized AI assistants (like Gemini) to understand the concept of Variadic Functions in C (va_list, va_start, va_end) and to debug syntax errors in my Makefile. The core logic of the printing functions was developed manually. I also discussed the code with peers and used the 42 Guide Gitbook, which was a very helpful resource.