C - printf

This project makes use of all the topics we have learned so far in ALX Low-level programming i.e loops, variables, pointers, function pointers, macros, directives, variadic functions etc.

In this group project, we re-create the C printf function.

The printf() function sends formatted output to stdout.

A custom _printf() for learning purposes was developed by Richard Orido and Chiagozie Mbiaku.

_printf() function format string is a character string, beginning and ending in its initial shift state, if any. These arguments are placed using the percentage % operator.

Compilation

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The code must be compiled this way:

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

As a consequence, be careful not to push any .c file containing a main function in the root directory of your project (you could have a test folder containing all your tests files including main functions)

The main files will include your main header file (main.h): #include main.h

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Use & Examples

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

Use - General: _printf("format string", var1, var2, ...);

Examples:

• Basic String: _printf("%s Alx", "Hello");

  • Output: Hello Alx

• Print integers: _printf("This is an array element: arr[%d]:%c", 32, arr[32]);

  • Output: This is an array element arr[32]:A

Many other specifiers and flags were added and by combining them generate a different ouput. The following list are the specifiers and flags allowed.

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Use & Examples

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Specifiers

Specifier	Output	Examples
c	Character	y
d or i	Signed integer	1024, -1024
s	String of characters	Hello Alx
b	Binary Representation of unsigned integer	01010110
u	Unsigned integer	1024
o	Unsigned octal	432
x	Unsigned hexadecimal integer	3ca
X	Unsigned hexadecimal integer (uppercase)	3CA
S	String with hex-ascii value replacing special chars	\x0A\x0A
p	Pointer address	0x403212
r	Reversed string of characters	dlroW olleH
R	ROT13 Translation of string	Uryyb

Flags

Flag	Description
-	Left-justify the output within the field width that was given; Right justification is the default (see width sub-specifier).
+	Preceeds the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded with a - sign.
(space)	If no sign is going to be written, a blank space is inserted before the value.
#	Used with o, x or X specifiers the value is preceeded with 0, 0x or 0X respectively for values different than zero.
0	Left-pads the number with zeroes (0) instead of spaces when padding is specified (see width sub-specifier).

Width

Width	Description
(number)	Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.
*	The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.

Precision

Precision

Description

.(number)

For integer specifiers (d, i, o, u, x, X): precision specifies the minimum number of digits to be written. If the value to be written is shorter than this number, the result is padded with leading zeros. The value is not truncated even if the result is longer. A precision of 0 means that no character is written for the value 0. For s: this is the maximum number of characters to be printed. By default all characters are printed until the ending null character is encountered. If the period is specified without an explicit value for precision, 0 is assumed.

Lenght modifiers

Modifier/Specifier	d & i	u, o, x, X	c	s	p
none	int	unsigned int	int	char pointer	void pointer
h	short int	unsigned short int
l	long int	unsigned long int

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Files contained in this repository

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Name	Description
main.h	Header file with the data type struct, standard libraries, macros, flags and custom prototypes.
_printf.c	Main printf function file. Calls other functions.
functions.c	Contains functions that print a character, string, percent sign, binary and integer.
functions1.c	Contains functions that print an unsigned integer number, unsigned number in octal, hexadecimal, upper hexadecimal, upper/lower hexadecimal.
functions2.c	Contains functions that print a pointer, non-printables, prints in reverse, and rot13.
get_flags.c	Function that calculates active flags.
get_precision.c	Function that calculates the precision for printing
get_size.c	Function that calculates the size to cast to argument.
get_width.c	Function that calculates the width for printing
handle_print.c	Function that prints an argument based on its type.
utils.c	Contains various utility functions.
_putchar.c	Custom putchar function.

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