The printf function sends formatted output to stdout. This project was curated for learning purposes by Eniola Olawunmi and Queen Unogwu in the Holberton & Alx scholarship program Cohort 9.
printf (print formatted) in C, writes out a cstring to stdout (standard output). The provided cstring may contain format specifiers( beginning with % in the cstring).
If there are format specifiers, those are replaced with their respective arguments that follow the cstring to the printf call. Source
- Secrets of printf by Don Colton https://www.cypress.com/file/54761/download
- Printf format string from Wikipedia https://en.m.wikipedia.org/wiki/Printf_format_string
- The Julia Language Manual https://docs.julialang.org/en/v1/stdlib/Printf/
- How to use the printf function in C by Educative https://www.educative.io/answers/how-to-use-printf-in-c
- 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)
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
Prototype: int _printf(const char *format, ...);
Use - General: _printf("format string", var1, var2, ...);
Examples:
-
Basic String: _printf("%s Hello, World!");`
- Output: Hello, World!
-
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 combinig those the _printf() function generate a different ouput. The following list are the specifiers and flags allowed.
| Specifier | Output | Examples |
|---|---|---|
c |
Character | y |
d or i |
Signed integer | 1024, -1024 |
s |
String of characters | Hello, world! |
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 | 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). |