🧵 ft_printf

ft_printf is a 42 project that recreates part of the behavior of the standard printf() function from libc.
It strengthens your skills in:

• handling variadic arguments (va_list)
• manual data formatting
• modular and clean C programming
• implementing flags and reproducing standard printf behavior

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🧠 Objective

Implement the function:

int ft_printf(const char *format, ...);

This function:

• Prints formatted output to stdout
• Supports several conversion specifiers
• Returns the number of characters printed
• Reproduces the behavior of the original printf for mandatory conversions

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🎨 Mandatory Part

✔ Implemented conversions

Specifier	Meaning	Example
%c	Character	'A'
%s	String	"Hello"
%p	Pointer (0x...) or (nil)	(nil)
%d	Signed integer	-42
%i	Signed integer	24
%u	Unsigned integer	42
%x	Hexadecimal (lowercase)	2a
%X	Hexadecimal (uppercase)	2A
%%	Prints %	%

✔ General rules

• Only write() may be used for printing
• Return value = total printed characters
• %p prints (nil) when the pointer is NULL
• Code must follow the 42 Norm

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⭐ Bonus Part

This project implements the bonus flag set allowed by the subject:

✔ Supported flags

Flag	Description	Example	Output
+	Always show the sign	%+d, 42	+42
(space)	Leading space for positive numbers	% d, 42	42
#	Hexadecimal prefix	%#x, 255	0xff

✔ Flag rules

• If + and are both used → + wins
• # only affects %x and %X
• # does not add prefix when the number is 0

According to the subject:

You only need to implement one bonus set.
This project implements: #, +, and space.

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📁 Project Structure

ft_printf/
├── ft_printf.c
├── ft_printf.h
├── ft_printf_utils.c
├── ft_flags_bonus.c
├── libft/
│   ├── *.c
│   └── libft.a
└── Makefile

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🔍 How It Works

1. ft_printf iterates through the format string
2. When it finds %, it checks:
   • flags
   • conversion type
3. It calls helper functions depending on the type
4. It prints numbers, strings, characters, hex, and pointers manually
5. It returns the number of characters printed

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⚙️ Compilation

Build the library:

make

Use it in your program:

cc -Wall -Wextra -Werror main.c libftprintf.a -I .

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🧪 Example Usage

int main(void)
{
    ft_printf("Char: %c\n", 'A');
    ft_printf("String: %s\n", "Hello");
    ft_printf("Pointer: %p\n", NULL);
    ft_printf("Decimal: %d\n", -42);
    ft_printf("Unsigned: %u\n", 4242);
    ft_printf("Hex: %x / %X\n", 255, 255);
    ft_printf("Percent: %%\n");
    
    // Bonus flags
    ft_printf("Plus flag: %+d\n", 42);
    ft_printf("Space flag: % d\n", 42);
    ft_printf("Hash flag: %#x\n", 255);
    
    return (0);
}

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🧾 Notes

• Fully compliant with the 42 Norm
• No forbidden functions
• Bonus is evaluated only if mandatory part is perfect
• %p must print (nil) for null pointers
• Every printed character must be counted precisely

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📜 License

This project is part of the 42 curriculum.
You may read and study the code — just make sure you truly understand it. ✨