How to write your printf in C

#include <stdarg.h>  // For handling variadic arguments
#include <stdio.h>   // For standard input/output
 
int print_integer(int value);
 
void print_buffer(char buffer[], int *buff_ind);
 
#define BUFF_SIZE 1024
 
int _printf(const char *format, ...)
{
	va_list args;      // Declare a variable to hold the list of arguments
	int count = 0;     // Initialize a counter for the number of characters printed
	int printed = 0;   // Number of characters printed by each conversion specifier
	int buff_ind = 0;  // Buffer index
	char buffer[BUFF_SIZE];
 
	va_start(args, format); // Initialize the argument list
 
	while (*format) // Iterate over each character in the format string
	{
		if (*format == '%') // Check for the start of a conversion specifier
		{
			format++; // Move to the next character after '%'
 
			if (*format == '%') // Case: '%%' prints a single '%'
			{
				buffer[buff_ind++] = '%';
				if (buff_ind == BUFF_SIZE)
				{
					print_buffer(buffer, &buff_ind);
					count += buff_ind;
				}
			} else if (*format == 'c') // Case: '%c' prints a character
			{
				int ch = va_arg(args, int); // Fetch the next argument as int
				buffer[buff_ind++] = ch;
				if (buff_ind == BUFF_SIZE)
				{
					print_buffer(buffer, &buff_ind);
					count += buff_ind;
				}
			} else if (*format == 's') // Case: '%s' prints a string
			{
				char *str = va_arg(args, char *); // Fetch the next argument as char*
				while (*str) // Iterate over each character in the string
				{
					buffer[buff_ind++] = *str;
					str++;
					if (buff_ind == BUFF_SIZE)
					{
						print_buffer(buffer, &buff_ind);
						count += buff_ind;
					}
				}
			} else if (*format == 'd' ||
			           *format == 'i') // Case: '%d' or '%i' prints an integer
			{
				int value = va_arg(args, int);
				printed = print_integer(value);//calling print_int function
				count += printed;
			}
		} else // Case: Regular character, not a conversion specifier
		{
			buffer[buff_ind++] = *format;
			if (buff_ind == BUFF_SIZE)
			{
				print_buffer(buffer, &buff_ind);
				count += buff_ind;
			}
		}
 
		format++; // Move to the next character in the format string
	}
 
	print_buffer(buffer, &buff_ind);
	count += buff_ind;
 
	va_end(args); // Clean up the argument list
 
	return count; // Return the number of characters printed
}
 
int print_integer(int value)
{
	char buffer[32]; // Buffer to store the string representation
	int printed = 0; // Counter for the number of characters printed
 
	// Handle the case of negative numbers
	if (value < 0)
	{
		putchar('-');
		printed++;
		value = -value;
	}
 
	// Convert each digit of the integer to a character
	int i = 0;
	do
	{
		buffer[i++] = '0' + (value % 10);
		value /= 10;
		printed++;
	} while (value > 0);
 
	// Print the characters in reverse order to get the correct representation
	for (int j = i - 1; j >= 0; j--)
	{
		putchar(buffer[j]);
	}
 
	return printed;
}
 
void print_buffer(char buffer[], int *buff_ind)
{
	if (*buff_ind > 0)
	{
		for (int i = 0; i < *buff_ind; i++)
		{
			putchar(buffer[i]);
		}
	}
 
	*buff_ind = 0;
}
 
// For testing the code
#include <stdio.h>
 
int main()
{
	int num = 123;
	char character = 'A';
	char string[] = "Hello, World!";
 
	printf("Printing an integer: %d\n", num);
	printf("Printing a character: %c\n", character);
	printf("Printing a string: %s\n", string);
 
	return 0;
}

$ gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c