A custom implementation of the printf function that supports various format specifiers, flags, and modifiers. This project demonstrates low-level string manipulation, memory management, and variadic functions in C.

printf/
├── include/          # Header files
│   └── main.h       # Main header with function prototypes and structures
├── src/             # Source files
│   ├── _printf.c    # Main printf implementation
│   ├── functions.c  # Basic format specifier handlers
│   ├── functions1.c # Additional format specifier handlers
│   ├── functions2.c # More format specifier handlers
│   └── ...         # Other implementation files
├── lib/             # Compiled library files
├── obj/             # Object files
├── tests/           # Test files
│   └── test_printf.c # Test suite
├── Makefile         # Build system
├── main.c           # Example usage
└── README.md        # This file

• Basic format specifiers: %c, %s, %d, %i, %u, %o, %x, %X, %p, %%
• Support for field width and precision
• Support for flags: -, +, 0, #, space
• Length modifiers: l, h
• Custom specifiers:
  • %b - Binary
  • %S - String with non-printable characters
  • %r - Reverse string
  • %R - ROT13 encoded string
• Buffer optimization for reduced system calls

%[flags][width][.precision][length]specifier

• %c - Character
• %s - String
• %d or %i - Signed decimal integer
• %u - Unsigned decimal integer
• %o - Unsigned octal
• %x or %X - Unsigned hexadecimal
• %p - Pointer address
• %b - Binary
• %S - String with non-printable characters
• %r - Reverse string
• %R - ROT13 encoded string
• %% - Literal %

• - - Left-justify within the given field width
• + - Forces to precede the result with a plus or minus sign
• 0 - Left-pads the number with zeroes instead of spaces
• # - Used with o, x or X specifiers adds 0, 0x or 0X respectively
• (space) - If no sign is going to be written, a blank space is inserted before the value

• GCC compiler
• GNU Make

# Build the library
make

# Build the main program
make main

# Run tests
make test

# Clean object files
make clean

# Full cleanup (objects and binaries)
make fclean

# Rebuild everything
make re

#include "include/main.h"

int main(void)
{
    int num = 42;
    _printf("Hello, %s!\n", "World");
    _printf("Number: %d\n", num);
    _printf("Binary: %b\n", num);
    _printf("Unsigned hex: %x\n", num);
    _printf("Address of num: %p\n", (void *)&num);
    return (0);
}

The project includes a comprehensive test suite in tests/test_printf.c. Run the tests using:

make test

The test suite compares the output of _printf with the standard printf function for various format specifiers and edge cases.

• On success: Returns the number of characters printed (excluding the null byte)
• On error: Returns -1

• Returns -1 if format string is NULL
• Handles memory allocation failures
• Validates format specifiers
• Checks for buffer overflow

1. Fork the repository
2. Create your feature branch
3. Commit your changes
4. Push to the branch
5. Create a new Pull Request

This project is open source and available under the MIT License.