Who knew printf() could be implemented ?

This repository contains C program for _printf() function written as part of the Low-level programming and Algorithm project at Holberton School. The program is the implementation of C language function printf() which prints the formatted output.

Project overview

Compilation:

All files will be compiled with gcc 4.8.4 using the flags: -Wall -Werror -Wextra -pedantic

gcc -Wall -Werror -Wextra -pedantic *.c

Betty coding style:

All files are written in C and follows the Betty coding style for Holberton School. For more detail, check this page:

Betty style documentation

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)
• _putchar(char c)

Function prototypes

All function prototypes used to compile _printf() are included in the header file holberton.h:

• int (*get_func(const char *format))(va_list);
• int _putchar(char c);
• int _printf(const char *format, ...);
• int print_str(va_list args);
• int print_char(va_list args);
• int print_pct(va_list args);
• int print_dec(va_list args);

File description

• _printf.c: - contains the function _printf()
• _putchar.c: - contains the function _putchar()
• man_3_printf: - manual page for _printf() function.
• get_functions.c - contains the function get_func()
• file_functions.c - contains the functions print_char, print_str and print_pct for the case of printing character, string and '%'
• file_func_dec_int.c - contains the function print_dec for the case of printing decimal and integer
• holberton.h - contains all headers, prototypes and structure declaration

Function description

int _printf(const char *format, ...)

This function produces output under the control of a format string that specifies how subsequent arguments (or arguments accessed via the variable-length argument of stdarg(3)) are converted for output.

The format string is composed of zero or more directives:

1. Ordinary characters that are copied unchanged to the output stream. (except %)
2. Conversion specifications, each of which results in fetching zero or more subsequent arguments. Each conversion specification starts with the character %, ends with a conversion specifier ( which is a letter).

The conversion specifier:

The conversion specifier is a letter that specifies the type of conversion to be applied. Our program includes the following conversion specifiers:

d: decimal number to be provided for printing.

i: integer to be provided for printing

c: character to be provided for printing

s: ...The const char * argument is expected to be a pointer to an array of character type (pointer to a string).

%: A per cent sign '%' is written. No argument is converted.

Return value:

Upon success, _printfs return the number of characters printed (excluding the null byte used to end output to strings) A negative 1 is returned if an output error is encountered.

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int (*get_func(const char *format))(va_list)

This function called by _printf() and checks for valid conversion specifier when it finds a '%' character. The *get_func function will check for the right conversion specifier. Upon valid specifier, it returns the corresponding function.

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int print_char(va_list args)

This function gets a variadic argument and prints each character of char type.

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int print_str(va_list args)

This function gets a variadic argument, traverse the string, and prints a character at a time.

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int print_pct(va_list args)

This function prints a per cent sign '%'.

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int _putchar(char c)

writes the character c to standard output

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Examples

 _printf("Negative:[%d]\n", -762534);
Output:   Negative:[-762534]

_printf("Character:[%c]\n", 'H');
Output:   Character:[H]

_printf("Actual     : %s\n", "holberton");
Output:    Actual     : holberton

Author

Battsetseg Yondongombo

Holberton School, Cohort 13

Natalia Ponsard

Holberton School, Cohort 13