C - printf

Table of contents

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Description
Objectives
Requirements
Instructions
Tech stack
Files description
Installation and how to use
Thanks
Authors

Description

This project is a recreation of the C library function printf, developed as part of the Holberton School curriculum.
It aims to handle formatted output to the standard output stream using only low-level system calls, while respecting strict constraints.

Objectives

At the end of this project, I should be able to explain to anyone, without the help of Google:

• How variadic functions work in C.
• How the va_list, va_start, va_arg, and va_end macros are used.
• The difference between low-level and high-level output functions.
• How to structure a large C project with multiple files and headers.
• How to manage group projects and pair programming effectively.
• How to write and use a custom man page.

Requirements

• My programs and functions will be compiled with gcc using the flags -Wall, -Werror, -Wextra, -pedantic and -std=gnu89.
• All my files should end with a new line.
• My code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl.
• I am not allowed to use global variables.
• No more than 5 functions per file.
• The prototypes of all my functions should be included in my header file called main.h.
• All my header files should be include guarded.

List of allowed functions and system calls.

• write (man 2 write)
• malloc (man 3 malloc)
• free (man 3 free)
• va_start (man 3 va_start)
• va_end (man 3 va_end)
• va_copy (man 3 va_copy)
• va_arg (man 3 va_arg)

Instructions

Mandatory

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.

Repo:

• GitHub repository: holbertonschool-printf.

---

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.

Repo:

• GitHub repository: holbertonschool-printf.

---

2. Just because it's in print doesn't mean it's the gospel

Create a man page for your function.

Repo:

• GitHub repository: holbertonschool-printf.

---

Advanced

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

Handle the following custom conversion specifiers:

• b: the unsigned int argument is converted to binary.

alex@ubuntu:~/c/printf$ cat main.c
#include "main.h"

/**
 * main - Entry point
 *
 * Return: Always 0
 */
int main(void)
{
    _printf("%b\n", 98);
    return (0);
}
alex@ubuntu:~/c/printf$ gcc -Wall -Wextra -Werror -pedantic -std=gnu89 main.c
alex@ubuntu:~/c/printf$ ./a.out
1100010
alex@ubuntu:~/c/printf$

Repo:

• GitHub repository: holbertonschool-printf.

---

4. 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.

Repo:

• GitHub repository: holbertonschool-printf.

---

Tech stack

Files description

FILES	DESCRIPTION
assets	Contains the resources required for the repository.
main.c	Test file showcasing _printf with various format specifiers.
main.h	Contains the main structure and the function prototypes.
_printf.c	Contains my main _printf function.
specifiers_handler.c	Contains the function for associating a specifier with the corresponding function.
mandatory_functions.c	Contains all my mandatory print functions.
advanced_functions.c	Contains all my advanced print functions.
man_3_printf	man page of the _printf function.
README.md	The README file you are currently reading 😉.

main.c is provided for demonstration purposes only and is not part of the mandatory project files.

Installation and how to use

Installation:

1. Clone this repository:
   • Open your preferred Terminal.
   • Navigate to the directory where you want to clone the repository.
   • Run the following command:

git clone https://github.com/fchavonet/holbertonschool-printf.git

2. Open the repository you've just cloned.

3. Compile the source code:

gcc -Wall -Werror -Wextra -pedantic -std=gnu89 -Wno-format *.c -o test_printf

A main.c test file is provided for demonstration purposes. You can modify it to try different format specifiers supported by _printf (see table below).

SPECIFIERS	DESCRIPTION
%c	Print a single character.
%s	Print a null-terminated string.
%%	Print a literal '%' character.
%d	Print a signed decimal number.
%i	Print a signed integer.
%b	Print an integer in binary (custom).
%u	Print an unsigned decimal number.
%o	Print an integer in octal.

How to use:

1. Run the program:

./test_printf

Expected output:

A
The cake is a lie!
%

42 is the answer to life, the universe, and everything...

42
-42

The number 42 converted into binary is 101010

4294967295
The number 42 converted into octal is 52

2. Open the MAN page:

man ./man_3_printf

If the file does not open, you may need to grant execution permissions first.

Thanks

• A big thank you to all my Holberton School peers for their help and support throughout this project.

Authors

Fabien CHAVONET

• GitHub: @fchavonet