Because ft_putstr & ft_putnbr aren't enough 😜
Printf is likely one of the most popular commands people see when learning a new programming language, and for a good reason. They are easy to understand and very powerful too. This is why learning to implement our own version of printf can help us better understand what happens internally when entering printf("Hello World")!
Our version of the printf function will be called ft_printf, and will be able to work with the following inputs:
- Specifiers
| Specifier | Description |
|---|---|
% |
Prints the percent character |
c |
Prints a character |
s |
Prints a string (array of characters) |
d,i |
Prints an integer |
p |
Prints pointer address (hex starting with 0x) |
u |
Prints an unsigned integer |
x |
Prints an unsigned hexadecimal integer (lowecase a-f) |
X |
Prints an unsigned hexadecimal integer (uppercase A-F) |
- Flags
| Flag | Description |
|---|---|
| (width) | Specifies the minimum width of the printed variable (adds spaces when necessary) |
| (precision) | Selects the minimum number of elements of the variable that are printed (Eg. number of chars from a string) |
- |
Pads text to the left (adds spaces to the right) |
0 |
Pads text with zeroes instead of spaces |
. |
Separates Width and Precision |
* |
Indicates that the Width or the Precision will be specified using an additional variable |
Our ft_printf function has the following prototype:
int ft_printf(const char *str, ...);The general idea of the function is to iterate over str and print normally until a % is read. From there, we parse the next elements until one of the Specifiers is found or until the end of the string \0 is reached, whichever comes first. The general structure of the elements we want to parse is the following:
%[Flags][Width].[Precision][Specifier]
As of July 2021, the subject for this project has changed, and the flags -0. are now part of the bonuses. Also the * flag is gone entirely, though I have decided to keep it in my version of the code, since it took a while to implement and I wish to keep it. Other flags we need to implement in this bonus part are:
| Bonus Flag | Description |
|---|---|
# |
Adds "0X" or "0x" to conversions with hexadecimal specifiers (excluding p) for values other than zero |
| (space) | A blank space is added provided that no sign is specified |
+ |
Adds a plus sign in front of positive numbers |
As this is quite a straightforward approach at printf, there are a few limitations to consider, namely:
- Our
ft_printfdoes not have buffer management, unlike the real printf - This implementation of printf doesn't handle overflows and unexpected inputs the same way the real printf would
- Our
ft_printfisn't nearly as powerful as the real prinft since many features are not included ft_printfrelies on our personal libft library, which makes it slower in performance when compared to the original printf
In order for you to test this printf, it is recommended that you install the following dependencies:
gcc clang python-norminette makeFor Linux users, it is also recommended to install valgrind (Leak checker)
- Testing the
ft_printffunction
git clone https://gitlab.com/madebypixel02/ft_printf.git
cd ft_printf
makeFeel free to replace your own libft inside the ft_printf folder
- Usage:
The makefile compiles all files from the src/ or srcb/ folders and saves the object files to the obj/ and objb/ folders. It then generates the output file libftprintf.a inside the bin/ folder. Here are some of the commands you can try:
make all Compiles the libftprintf.a file
make test Compiles ft_printf and libft with a custom main. Checks for leaks in Mac and Linux
make bonus Compiles all bonus files instead of the mandatory ones
make norminette Checks Norm for both printf and libft files
make git Stages every modified file to commit and pushes to upstream branch
- Example:
This was my second project as a 42 student in Madrid. Looking forward to the new projects coming next!
July 9th, 2021