mudeitsi / printf

printf Partner Project

0x11. C - printf

ABOUT PRINTF

printf format string

The printf format string is a control parameter used by a class of functions in the input/output libraries of C and many other programming languages.

The string is written in a simple template language: characters are usually copied literally into the function's output, but format specifiers, which start with a % character, indicate the location and method to translate a piece of data (such as a number) to characters.

"printf" is the name of one of the main C output functions, and stands for "print formatted".

printf format strings are complementary to scanf format strings, which provide formatted input (lexing aka. parsing).

In both cases these provide simple functionality and fixed format compared to more sophisticated and flexible template engines or lexers/parsers, but are sufficient for many purposes.

Many languages other than C copy the printf format string syntax closely or exactly in their own I/O functions.

Mismatches between the format specifiers and type of the data can cause crashes and other vulnerabilities.

The format string itself is very often a string literal, which allows static analysis of the function call.

However, it can also be the value of a variable, which allows for dynamic formatting but also a security vulnerability known as an uncontrolled format string exploit.

This project is the application of the print f format string in C programming language.

MANDATORY TASKS:

0. I'm not going anywhere. You can print that wherever you want to. I'm here and I'm a Spur for life

Write a function that produces output according to a format.

Prototype: int _printf(const char *format, ...);

Returns: the number of characters printed (excluding the null byte used to end output to strings)

write output to stdout, the standard output stream

format is a character string. The format string is composed of zero or more directives. See man 3 printf for more detail. You need to handle the following conversion specifiers:

c s %

You don’t have to reproduce the buffer handling of the C library printf function

You don’t have to handle the flag characters

You don’t have to handle field width

You don’t have to handle precision

You don’t have to handle the length modifiers

1. Education is when you read the fine print. Experience is what you get if you don't

Handle the following conversion specifiers:

d i

You don’t have to handle the flag characters

You don’t have to handle field width

You don’t have to handle precision

You don’t have to handle the length modifiers

ADVANCED TASKS:

2. With a face like mine, I do better in print

Score: 0.0% (Checks completed: 0.0%) Handle the following custom conversion specifiers:

b: the unsigned int argument is converted to binary

3. What one has not experienced, one will never understand in print

Handle the following conversion specifiers:

u o x X

You don’t have to handle the flag characters

You don’t have to handle field width

You don’t have to handle precision

You don’t have to handle the length modifiers

4. Nothing in fine print is ever good news

Use a local buffer of 1024 chars in order to call write as little as possible.

5. My weakness is wearing too much leopard print

Handle the following custom conversion specifier:

S : prints the string.

Non printable characters (0 < ASCII value < 32 or >= 127) are printed this way: \x, followed by the ASCII code value in hexadecimal (upper case - always 2 characters)

6. How is the world ruled and led to war? Diplomats lie to journalists and believe these lies when they see them in print

Handle the following conversion specifier: p.

You don’t have to handle the flag characters

You don’t have to handle field width

You don’t have to handle precision

You don’t have to handle the length modifiers

7. The big print gives and the small print takes away

Handle the following flag characters for non-custom conversion specifiers:

space

8. Sarcasm is lost in print

Handle the following length modifiers for non-custom conversion specifiers:

l h

Conversion specifiers to handle: d, i, u, o, x, X

9. Print some money and give it to us for the rain forests

Handle the field width for non-custom conversion specifiers.

10. The negative is the equivalent of the composer's score, and the print the performance

Handle the precision for non-custom conversion specifiers.

11. It's depressing when you're still around and your albums are out of print

Handle the 0 flag character for non-custom conversion specifiers.

12. Every time that I wanted to give up, if I saw an interesting textile, print what ever, suddenly I would see a collection

Handle the - flag character for non-custom conversion specifiers.

13. Print is the sharpest and the strongest weapon of our party

Handle the following custom conversion specifier:

r : prints the reversed string

14. The flood of print has turned reading into a process of gulping rather than savoring

Handle the following custom conversion specifier:

R: prints the rot13'ed string

All the above options work well together.