_printf

A formatted output conversion C program completed as part of the low-level programming and algorithm track at ALX/Holberton School. The program is a pseudo- recreation of the C standard library function, printf.

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

Dependencies

The _printf function was coded on an Ubuntu 20.04.1 LTS machine with gcc version 9.4.0.

Usage

To use the _printf function, assuming the above dependencies have been installed, compile all .c files in the repository and include the header main.h with a main function.

Example main.c:

#include "main.h"
int main(void)
{
    _printf("Hello, %s!\n", "world");
    return (0);
}

Compilation:

$ gcc *.c -o printf
$

Output:

$ ./tester
Hello, World!
$

Description

The function _printf writes a formatted string to standard output. The function interpolates variable arguments (accessed via the variable-length argument facilities of stdarg) into the format string at the location of a corresponding conversion specifier.

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

Return Value

Upon successful return, _printf returns the number of characters printed (excluding the terminating null byte used to end output to strings). If an output error is encountered, the function returns -1.

Format of the Argument String

The format string argument is a constant character string composed of zero or more directives: ordinary characters (not %) which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments. Conversion specification is introduced by the character % and ends with a conversion specifier. In between the % character and conversion specifier, there may be (in order) zero or more flags, an optional minimum field width, an optional precision and an optional length modifier. The arguments must correspond with the conversion specifier, and are used in the order given.

Examples

String

• Input: _printf("%s\n", 'This is a string.');
• Output: This is a string. Character
• Input: _printf("The first letter in the alphabet is %c\n", 'A');
• Output: The first letter in the alphabet is A Integer
• Input: _printf("There are %i dozens in a gross\n", 12);
• Output: There are 12 dozens in a gross Decimal:
• Input: _printf("%d\n", 1000);
• Output: 1000

Project Requirements

• All files will be compiled on Ubuntu 14.04 LTS
• Programs and functions will be compiled with gcc 4.8.4 using flags -Wall -Werror -Wextra and -pedantic
• Code must follow the Betty style
• Global variables are not allowed
• Authorized functions and macros:
  • 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)

Mandatory Tasks

• Write function that produces output with conversion specifiers c, s, and %.

• Handle conversion specifiers d, i.

Advanced Tasks

• Handle conversion specifier b.

• Handle conversion specifiers u, o, x, X.

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

• Handle conversion specifier S.

• Handle conversion specifier p.

• Handle flag characters +, space, and # for non-custom conversion specifiers.

• Handle length modifiers l and h for non-custom conversion specifiers.

• Handle the field width for non-custom conversion specifiers.

• Handle the precision for non-custom conversion specifiers.

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

• Handle the custom conversion specifier r that prints the reversed string.

• Handle the custom conversion specifier R that prints the rot13'ed string.

• All above options should work well together.

File Descriptions

• _printf.c: - defines the function _printf, which uses the prototype int_printf(const char *format, ...);. The format string is composed of zero or more directives. See man 3 printf for more details. _printf will return the number of characters printed (excluding the null byte used to end output to strings) and will write the output to stdout, the standard output stream.
• main.h: - contains all function prototypes, macros, and structs used for _printf.
• handlers.c: - contains the function specifier_handler which maps conversion specifiers to a corresponding callback function, and executes the function that matches the provided specifier.
• char_converters.c: - handles all char/string convertions and contains the functions convert_str, and convert_char, which handle the conversion specifiers s and c, respectively.
• base_converters.c: - handles all base conversions and contains the functions convert_bin, convert_oct, convert_hex and, convert_hexa, which handle the conversion specifiers b, o, x, and X, respectively.
• int_converters.c: - handles all integer conversions and contains the functions convert_int, convert_uint, and convert_addr, which handle the conversion specifiers i, u, and p, respectively.
• misc_converters.c - handles all miscelleneous convertions and contains the function convert_percent, which handles the conversion specifier %.

Acknowledgements 🙏

The _printf function emulates functionality of the C standard library function printf.

This program was written as part of the curriculum for ALX/Holberton School. ALX is a remote full-stack software engineering program that prepares students for careers in the tech industry using project-based peer learning. For more information, visit this link.

Authors

Ifedayo Ijabadeniyi

Odusanya Ibukun