0x11. C - printf - We write our own printf function.

Resources

• Secrets of printf
• Group Projects
• Flowharts

Requirements

• Formats and programs will be compile with gcc 4.8.4
• All files should be compiled with Ubuntu 14.04 LTS
• The prototypes of all your functions and the prototype of the function _putchar should be included in your header file called holberton.h
• You might want to look at the gcc flag -Wno-format when testing with your _printf and the standard printf
• Main files will include your main header file (holberton.h): #include holberton.h

In This Project We Should Learn

• printf
• format specifiers

printf

Is a function native of the C programming language, used to print a string format. the prototype can be something like this:

int printf(const char* format,...)

The string is written in a simple template language. The constant string format provides a description of the output which start with a % character, indicate the location and method to translate a piece of data (such as a number) to characters. e.g:

printf("Color %s, numbero1 %d, numbero2 %05d, hex %x, real %5.2f.\n", "red", 12345, 69, 555, 3.14);

The output will be the folowing one (inluding the \n character):

color red, numbero1 12345, numbero2 00069, hex ff, real 3.14.

The printf function returns the number of characters printed, or a negative value if an error occurs.

The classic Hello world example:

#include <stdio.h>
 
int main(void)
{
    printf("Hello, world!\n");
    return (0);
}

format specifiers

Printf allows to specify format to the output. Here some examples:

Format Output

• %d ó %i integer in base 10 with (int)sign printf ("integer number in base 10 is: %d" , -10);
• %c carácter (char)
• %s string od characteres (string) print_char

Diagrams

check our diagrams here