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14 Nov 01:32
@OusamaTheCoder OusamaTheCoder
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0x11. C - printf

Description

printf.jpg

The printf function sends formatted output to stdout. A custom _printf() for learning purposes was developed by cohort 19 students Ousama and Fatima. The _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.

Resources

  • Secrets of printf by Don Colton

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)

Compilation ⚗️

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 test files, including main functions).

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

#include "main.h"

Use & Examples

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

General Usage:

_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

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; Right justification is the default.
+ Precedes 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 preceded 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:

  • (number): Minimum number of characters to be printed. If the value is shorter than this number, it 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:

  • .(number): For integer specifiers (d, i, o, u, x, X), precision specifies the minimum number of digits to be written. If the value is shorter than this number, the result is padded with leading zeros. 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. If the period is specified without an explicit value for precision, 0 is assumed.

Length 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

Files contained in this repository

Name Information Relevant Files
main.h Header file with the data type struct, standard libraries and custom prototypes. *.c compilation
_printf.c Main printf function file. Calls other functions. _printf.c
_put.c Custom putchar function. _put.c
convert_number.c Functions for number conversion. convert_number.c
main.c Main testing file. main.c
number.c Functions for handling number specifiers. number.c
params.c Functions for handling parameter specifiers. params.c
print_functions.c Functions for printing various data types. print_functions.c
print_number.c Functions for printing numbers. print_number.c
simple_printers.c Simple printing functions. simple_printers.c
specifier.c Functions for handling specifiers. specifier.c
string_fields.c Functions for handling string specifiers. string_fields.c

Tasks required for this project

  1. Write a function that produces output according to a format. Handle the following conversion specifiers: c, s, %.
  2. Handle the following conversion specifiers: d, i.
  3. Handle the following custom conversion specifiers: b: the unsigned int argument is converted to binary.
  4. Handle the following conversion specifiers: u, o, x, X.
  5. Handle the following conversion specifier: p.
  6. Handle the following flag characters for non-custom conversion specifiers: +, space, #.
  7. Handle the following length modifiers for non-custom conversion specifiers: l, h.
  8. Conversion specifiers to handle: d, i, u, o, x, X.
  9. Handle the field width for non-custom conversion specifiers.
  10. Handle the precision for non-custom conversion specifiers.
  11. Handle the 0 flag character for non-custom conversion specifiers.
  12. Handle the - flag character for non-custom conversion specifiers.
  13. Handle the following custom conversion specifier: r: prints the reversed string.
  14. Handle the following custom conversion specifier: R: prints the rot13'ed string.
  15. All the above options work well together.

Disclaimer

If you happen to use this repo, we scored 184.29%.

Authors ©

Full Changelog: https://github.com/OusamaTheCoder/printf/commits/My_projects_in_C_language%22

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