_printf

Simulation of C printf function

_printf is a function that produces output according to a format. Writes at most size bytes (including the terminating null byte ('\0')) to str.

Synopsis:

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

• format is a character string. The format string is composed of zero or more directives and conversion specifiers: %c, %s, %d, %i, %%, %o, %u, %x, %X, %p (custom conversion specifiers: %r, %R, %b).

• (...) are the variable number of input arguments separated by comma (optional).

Returns:

• Upon successful return, the number of characters printed (excluding the null byte used to end output to strings).
• Write output to stdout, the standard output stream.
• If an output error is encountered, a negative value (-1) is returned.

Examples:

Character (%c):

• Input: _printf("This is a char: [%c]\n", 'C');
• Output: This is a char: [C]

String (%s):

• Input: _printf("This is a string: [%s]\n", "Hello World");
• Output: This is a string: [Hello World]

Number (%i):

• Input: _printf("This is a number: [%i]\n", 20);
• Output: This is a number: [20]

Number (%d):

• Input: _printf("This is another number: [%d]\n", 156);
• Output: This is another number: [156]

Percentage (%%):

• Input: _printf("Printing a percentage: [%%]\n");
• Output: Printing a percentage: [%]

Character string without conversion specifications:

• Input: _printf("Hello World");
• Output: Hello World

Print an unsigned decimal argument (%u):

• Input: _printf("Unsigned wNeg (with Negative): [%u], -123");
• Output: Unsigned wNeg (with Negative): [4294967173]

Print an unsigned int argument converted to octal notation (%o):

• Input: _printf("98 in octal notation is: [%o], 98");
• Output: 98 in octal notation is: [142]

Print an unsigned int argument converted hexadecimal (x) notation (%x):

• Input: _printf("2035495 in hexadecimal (x) notation is: [%x], 2035495");
• Output: 2035495 in hexadecimal (x) notation is: [1f0f27]

Print an unsigned int argument converted hexadecimal (X) notation (%X):

• Input: _printf("2035495 in hexadecimal (X) notation is: [%X], 2035495");
• Output: 2035495 in hexadecimal (X) notation is: [1F0F27]

Print a memory address (%p): The argument shall be a pointer to void. The value of the pointer is converted to a sequence of printing characters, in an implementation-defined manner.

• Input: _printf("Address:[%p]\n", addr); //----> where 'addr' is addr = (void *)0x7ffe637541f0;
• Output: Address:[0x7ffe637541f0]

Custom conversion specifiers examples:

Print a string in reverse (%r):

• Input: _printf("String in [%r]\n", "reverse");
• Output: String in [esrever]

Print a string in rot13 (%R):

• Input: _printf("Hello World in rot13 is: [%R]\n", "Hello World");
• Output: Hello World in rot13 is: [Uryyb Jbeyq]

Unsigned int argument converted to binary (%b):

• Input: _printf("98 in binary: [%b]\n", 98);
• Output: 98 in binary: [1100010]

Resources

• Secrets of printf
• printf(3) - Linux man page
• Variadic Functions
• Variable Arguments in C
• Function Pointers
• typedef
• Structures in C language

Requirements

• gcc 4.8.4
• All files should be compiled with Ubuntu 14.04 LTS
• The prototypes of all functions, structures and libraries are included in the header file called holberton.h
• 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)

Authorized libraries

• stdarg.h
• stdlib.h
• unistd.h

Files

File	Description
_printf.c	Function that prints according to a given format
_putchar.c	writes the character c to stdout
_puts.c	prints a string
call_print_functions.c	Auxiliary functions
check_for_format.c	Check printf format specifiers
holberton.h	Include prototypes, strucs, libraries.
inp_out.c	Check /and print input/output
man_3_printf	_printf Man Page
print_number.c	Auxiliary function
printf_advanced.c	Advanced Task - Prints a reversed string
printf_advanced_base.c	Advanced Task - Unsigned int argument is converted to binary
printf_advanced_base2.c	Advanced Task - Print unsigned, octal, hexadecimal notation
printf_advanced_rot13.c	Advanced Task - Prints rot13'ed string
printf_advanced_pointer.c	Advanced Task - Prints a memory address in C

Compilation

Code files must be compiled this way:

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

Flowcharts

https://drive.google.com/file/d/1V-SUvg7jqLFF5P20Prx_qDa7WkukhqG7/view?usp=sharing

Authors

• Andrés Bayona | Github
• Tatiana Orejuela | Github

Holberton School - Foundations - Low-level programming & Algorithm

March, 2020.