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0x11. C - Printf

Description

This project is a team project with the objectif of replicates the C standard library printf() function. The function printf is a collection of files.c that when compiled and executed, produces output according to a format.


Prototype

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

Usage

  • Prints a string to the standard output, according to a given format
  • All files were created and compiled on Ubuntu 14.04.4 LTS using GCC 4.8.4 with the command gcc -Wall -Werror -Wextra -pedantic *.c
  • Returns the number of characters in the output string on success, -1 otherwise
  • Call it this way: _printf("format string", arguments...) where format string can contain conversion specifiers and flags, along with regular characters

Format Specifier

Specifier Description
%s print a string of characters
%c print a single character
%% print a percent sign (% also works)
%d print a decimal (base 10) number
%i print an integer in base 10
%b print a number or a character as binary
%u print an unsigned integer
%o print an unsigned integer in base 8
%x print an unsigned integer in base 16
%X same as %x, but the letters are in uppercase
%S same as %s, but the non-printable characters
%p print an adresse
%r print a string in reverse
%R print a string encoded in rot13

Flag Characters

Flag Description
+ A sign (+ or -) is placed before a number produced by a signed conversion.
' ' (a space) A blank space is put before the number if the number is positive.
# The value takes an alternate form. For o conversions, the first character of the output is 0 except if the number to be printed is not zero already. In case of a x or X conversions, if the number to output is different of zero, 0x (in case of x) or OX (in case of X) are the first characters to be printed before the number.

Examples

   _printf("%i", 2); Output : 2

   _printf("%b", 7); Output : 111

   _printf("%u", 3147593600); Output : 3147593600

   _printf("%o", 90); Output : 132

   _printf("%x", 908); Output : 38c

   _printf("%X", 1115); Output : 45B

   _printf("%S", "Best\nSchool"); Output : Best\x0ASchool

   _printf("%p", (void *)0x7ffe637541f0); Output : 0x7ffe637541f0

   _printf("%r", "Hello!"); Output : !olleH

   _printf("%R", "My message"); Output : Zl zrffntr

Tasks

These are all the tasks of this project, the ones that are completed link to the corresponding files.

  • Write a function that produces output according to format.
    • c : converts input into a character
    • s : converts input into a string
  • Handle the following conversion specifiers:
    • d : converts input into a base 10 integer
    • i : converts input into an integer
  • Create a man page for your function
  • Handle the following conversion specifiers:
    • b : the unsigned int argument is converted to binary
  • Handle the following conversion specifiers:
    • u : converts the input into an unsigned integer
    • o : converts the input into an octal number
    • x : converts the input into a hexadecimal number
    • X : converts the input into a hexadecimal number with capital letters

[5. Nothing in fine print is ever good news]

  • Use a local buffer of 1024 chars in order to call write as little as possible.
  • Handle the following custom conversion specifier:
    • S : prints the string
    • Non printable characters (0 < ASCII value < 32 or >= 127) are printed this way: \x, followed by the ASCII code value in hexadecimal (upper case - always 2 characters)
  • Handle the following conversion specifier:
    • p : int input is converted to a pointer address
  • Handle the following flag characters for non-custom conversion specifiers:
    • + : adds a + in front of signed positive numbers and a - in front of signed negative numbers
    • space : same as +, but adds a space (is overwritten by +)
    • # : adds a 0 in front of octal conversions that don't begin with one, and a 0x or 0X for x or X conversions

[9. Sarcasm is lost in print]

  • Handle the following length modifiers for non-custom conversion specifiers:
    • l : converts d, i, u, o, x, X conversions in short signed or unsigned ints
    • h : converts d, i, u, o, x, X conversions in long signed or unsigned ints

[10. Print some money and give it to us for the rain forests]

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

[11. The negative is the equivalent of the composer's score, and the print the performance]

  • Handle the precision for non-custom conversion specifiers.

[12. It's depressing when you're still around and your albums are out of print]

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

[13. Every time that I wanted to give up, if I saw an interesting textile, print what ever, suddenly I would see a collection]

  • Handle the - flag character for non-custom conversion specifiers.
  • Handle the following custom conversion specifier:
    • r : prints the reversed string
  • Handle the following custom conversion specifier:
    • R : prints the rot13'ed string

[16. * ]

  • All the above options work well together.

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