ft_printf

ft_printf is reproduced C's printf function. Just like real printf, it allows the following functionality:

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

Result is a formated string. Each of these parts is explained below. To produce ft_printf() function, only UNIX write, malloc, free, exit, stdarg functions have been used. Rest of the functionality is custom built.

Project folder structure

ft_printf
├── includes [header file for project]
├── libft [my library with various functions]
└── srcs [source files of the project]
Makefile [compiles the project]
author [my username]

Getting Started

Run make, which results in library called libftprintf.a. In your source file, use ft_printf() function just as you would use printf(). Furthermore, compile your source code with libftprintf.a to use ft_printf() function. So libftprint.a includes the ft_printf() function.

gcc main.c libftprintf.a

Functionality

[flags]

Following flags are supported

'#'(hash) - For o, x, X types, the text 0, 0x, 0X, respectively, is prepended to non-zero numbers.

'0'(zero) - When the 'width' option is specified, prepends zeros for numeric types.
For example, printf("%2X",3) produces ' 3', while printf("%04X",3) produces '0003'.

'-'(minus) - Left-align the output of this placeholder. (The default is to right-align the output.)

'+'(plus) - Prepends a plus for positive signed-numeric types.

' '(space) - Prepends a space for positive signed-numeric types.This flag is ignored if the + flag exists.

[width]

Width specifies a minimum number of characters to output. For example, ft_printf("%5d", 5); would result in ' 5';

[.precision]

Precision field specifies a maximum limit on the output. For example, ft_printf("%.2s", "abcd"); would result in 'ab';

[length]

Length specifiers tell what argument is expected. It will cause ft_printf() to typecast the input to meet necessary requirement.

Allowed length specifiers

'l' - For integer types, causes ft_printf to expect a long-sized integer argument.
'L' - For floating point types, causes ft_printf to expect a long double argument.
'hh' - For integer types, causes ft_printf to expect an int-sized integer argument which was promoted from a char.
'h' - For integer types, causes ft_printf to expect an int-sized integer argument which was promoted from a short.
'l' - For integer types, causes ft_printf to expect a long-sized integer argument.
'll' - For integer types, causes ft_printf to expect a long long-sized integer argument.

type

Following conversion characters are allowed:

%c (character)
%s (string)
%p (address)
%d (digit)
%i (integer)
%o (digit in octal)
%u (unsigned integer)
%x (hexadecimal in lowercase)
%X (hexadecimal in upper case)
%f (float)

Furthermore, ft_printf supports multibyte characters. For multibyte character argument must have L in front of it indicating that it consists of wide characters. If multibyte character or string are printed, their respective conversion character has to be in capital. For example, to print '→' character, %c becomes %C. If you wish, you can also print emojis.

ft_printf("%C", L'→'); Outputs '→'.
ft_printf("%C", L'😊'); Outputs '😊'

Return value

Function returns bytes written to standard output. Thus, if multibyte character is printed, ft_printf() would return the amount of bytes it consists of not how many characters were printed.

Example

Following program

int main(void)
{
  ft_printf("I use %f%Cs to buy %s\n", 9.23, L'€', "groceries");
}

Would produce following output

I use 9.230000€s to buy groceries.

Notably, the float has 6 digits after comma, because that is how default printf() functions, if no width has been specified.