printf

An implementation of the printf function as defined by the C89 standard with some custom format specifiers.

Description

The printf function converts, formats, and writes it's arguments to stdout under the control of format.
On success, it returns the number of characters written, or a negative value if an error occured.
The format string contains two types of objects: ordinary characters, which are copied to the output stream, and format specifiers, each of which causes conversion and printing of the next successive argument to printf.
A format specifier follows this prototype: %[flags][width][.precision][length]specifier

Features

This section covers all the format specifiers and sub-specifiers supported by our _printf function.

Format Specifiers

specifier	Output
%d or %i	Signed decimal integer
%u	Unsigned decimal integer
%o	Unsigned octal
%x	Unsigned hexadecimal integer (lowercase)
%X	Unsigned hexadecimal integer (uppercase)
%c	Single character
%s	String of characters
%p	Pointer address
%%	Single %
%b	Unsigned binary integer
%r	Reversed string
%R	Rot13'd string
%S	String of characters, non-printable characters are converted to their hex value

Sub-specifiers

1. Flags:

• minus flag
• plus flag
• space flag
• zero flag
• hash flag

2. Width:

• number
• asterisk

3. Precision:

• .number
• asterisk

4. Length Modifiers:

• h
• l (ell)

Usage

The simplest way to add our _printf function to your project is by cloning the source code into your own project tree, then creating a static library from it:

$ git clone https://github.com/iamkhalil/printf.git
$ cd printf
$ make

You can now use our _printf as a static library with your C applications:

$ gcc myapp.c -L. -lprintf -o myapp

Examples

$ cat myapp.c
#include <stdio.h>
#include "printf.h"

int main(void)
{
	const char *s = "Hello";
	int real, mine;
	void *addr;

	real = printf("Hello, world!\n");
	mine = _printf("Hello, world!\n");
	_printf("Length: [%d, %d]\n", real, mine);

	_printf("Strings:\n");
	_printf(" padding:\n");
	printf("\t[%10s]\n", s);
	_printf("\t[%10s]\n", s);
	printf("\t[%-10s]\n", s);
	_printf("\t[%-10s]\n", s);
	printf("\t[%*s]\n", 10, s);
	_printf("\t[%*s]\n", 10, s);
	_printf(" truncating:\n");
	printf("\t%.4s\n", s);
	_printf("\t%.4s\n", s);
	printf("\t%.*s\n", 3, s);
	_printf("\t%.*s\n", 3, s);

	printf("Characters:\t%c %%\n", 'A');
	_printf("Characters:\t%c %%\n", 'A');

	_printf("Integers:\n");
	real = printf("\tDecimal:\t%i %d %.6i %i %.0i %+i %i\n", 1, 2, 3, 0, 0, 4, -4);
	mine = _printf("\tDecimal:\t%i %d %.6i %i %.0i %+i %i\n", 1, 2, 3, 0, 0, 4, -4);
	_printf("\tLength: [%d, %d]\n", real, mine);
	printf("\tUnsigned:\t%6.4u\n", 42);
	_printf("\tUnsigned:\t%6.4u\n", 42);
	printf("\tHexadecimal:\t%x %x %X %#x\n", 5, 10, 10, 6);
	_printf("\tHexadecimal:\t%x %x %X %#x\n", 5, 10, 10, 6);
	printf("\tOctal:\t\t%o %#o %#o\n", 10, 10, 4);
	_printf("\tOctal:\t\t%o %#o %#o\n", 10, 10, 4);

	addr = (void *)0x7fff1038675c;
	printf("Address:[%p]\n", addr);
	_printf("Address:[%p]\n", addr);

   	printf("\nCustom format specifiers:\n");
	_printf(" Reverse:\t[%r]\n", "Live");
	_printf(" Rot13:\t[%R]\n", "SHA");

	return 0;
}

$ gcc -Wall -Werror -Wextra -pedanitc *.c -o myapp
$ ./myapp
Hello, world!
Hello, world!
Length: [14, 14]
Strings:
 padding:
	[     Hello]
	[     Hello]
	[Hello     ]
	[Hello     ]
	[     Hello]
	[     Hello]
 truncating:
	Hell
	Hell
	Hel
	Hel
Characters:	A %
Characters:	A %
Integers:
	Decimal:	1 2 000003 0  +4 -4
	Decimal:	1 2 000003 0  +4 -4
	Length: [30, 30]
	Unsigned:	  0042
	Unsigned:	  0042
	Hexadecimal:	5 a A 0x6
	Hexadecimal:	5 a A 0x6
	Octal:		12 012 04
	Octal:		12 012 04
Address:[0x7fff1038675c]
Address:[0x7fff1038675c]

Custom format specifiers:
 Reverse:	[eviL]
 Rot13:	[FUN]

Author

• Mohamed khalil El-Bechir - medkhalilelb@gmail.com | GitHub/iamkhalil

Licence

MIT License