ft_printf

A custom-built version of the standard printf function in C, developed as part of the 42 school curriculum. The goal was to implement a simplified version that handles a range of format specifiers and argument types, while ensuring robust error handling and proper memory management.

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Variadic Functions in C

What is a Variadic Function?

A variadic function in C is a function that can accept a variable number of arguments. A common example is the standard printf function, which adjusts its behavior based on a format string and accompanying arguments. These functions are declared with an ellipsis (...) to indicate that additional unnamed arguments may be passed:

int	ft_printf(const char *format, ...)
{
	va_list	args;
	int		count;

	va_start(args, format);
	count = check_format(args, format);
	va_end(args);
	return (count);
}

How Do They Work?

Variadic functions use the <stdarg.h> header, which provides macros to handle the variable arguments:

• va_list
  A data type used to declare a variable that can access a function's unnamed (variadic) arguments.
• va_start(args, format)
  Initializes a list of type va_list to start reading arguments, beginning after the string format.
• va_arg(args, type)
  Retrieves the next argument in the list, specifying its type.
• va_end(vargs)
  Cleans up after accessing the arguments.

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🔧 What Was Implemented

A custom version of printf that supports the following format specifiers:

• %c : character
• %s : string
• %p : pointer
• %d / %i : signed integer
• %u : unsigned integer
• %x : hexadecimal (lowercase)
• %X : hexadecimal (uppercase)
• %% : percent sign

Additional features:

• Custom memory handling for dynamic buffers and edge cases
• Error handling (e.g., printing (null) or (nill) for NULL strings)

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🔧 Project Structure

File Overview

• ft_check_flag.c
  Delegates to helper functions based on format specifiers to handle printing and update the character count.

• ft_print_decimal.c
  Prints a signed decimal integer (%d/%i) to standard output and updates the character count.

• ft_print_number_hex.c
  Prints an unsigned integer in lowercase (%x) or uppercase (%X) hexadecimal format and updates the character count.

• ft_print_pointer.c
  Prints the address of a pointer in hexadecimal format, prefixed with 0x, and updates the character count.

• ft_print_udecimal.c
  Prints an unsigned decimal integer (%u) to standard output and updates the character count.

• ft_print_char.c
  Prints a character (%c) to standard output and updates the character count.

• ft_printf.c
  The main entry point of the custom printf implementation. Parses the format string and handles variadic arguments.

• ft_print_percent.c
  Prints the percent sign (%%) and updates the character count.

• ft_print_string.c
  Prints a string (%s) to standard output and updates the character count.

• Makefile
  Builds the static library libftprintf.a, which includes the ft_printf function.

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🛠️ Compilation

To compile the library, run:

make

To delete the files, run:

make fclean

To recompile the files , run:

make re

if you want to use the ft_printf function, then include the header file ft_printf.h in your source file, run:

cc main.c libftprintf.a

💡 Usage Example

#include "ft_printf.h"

int main(void)
{
    ft_printf("Hello %s! You are %d years old.\n", "Alice", 30);
    return 0;
}

Output:

Hello Alice! You are 30 years old. 

Testing

Basic unit tests were created to validate the correctness of the implementation by comparing output with the standard printf. You can find the tests in the test.c file.