GET NEXT LINE

In this project, I created a function that returns every next line of a text file each time we call it. The prototype looks like this :

char	*get_next_line(int fd)
{
	...
	return (line);
}

As you can see it takes a file descriptor as argument and returns a char string. The file descriptor corresponds to the open file you wanna read from. Here is an example of get_next_line function :

int	main(void)
{
	int		fd;

	fd = open("text.txt", O_RDWR);
	/// we use printf directly to display the char string returned by get_next_line ///
	printf("Here is the first line of the file text : %s", get_next_line(fd));	
}

In the picture above, you can firstly notice that we compiled with a flag "-D BUFFER_SIZE=10". BUFFER_SIZE is a variable corresponding to the number of characters read each time by read function. It means that we've made a function get_next_line that returns the first next line of a text file even if BUFFER_SIZE is a very large number or if it's equal to 1. That was a specific rule mentioned in our subject. Right after the compilation line you can see that text.txt contains 2 lines and finally right after the cat call you see that gnl returned only the first line. Here's a second example with multiple lines and multiple calls of this function (obviously, I added some lines to text.txt) :

int	main(void)
{
	int		fd;

	fd = open("text.txt", O_RDWR);
	printf("Here is the first line of the file text : %s", get_next_line(fd));
	printf("Here is the second line of the file text : %s", get_next_line(fd));
	printf("Here is the third line of the file text : %s", get_next_line(fd));
	printf("Here is the fourth line of the file text : %s", get_next_line(fd));
	printf("Here is the last line of the file text : %s", get_next_line(fd));
}

To make sure that our get_next_line function returns each time the very next line in a specific file we use a "static" variable that keeps track of the position in the text file after each function call. Here's a quick explanation from GeeksforGeeks to help you understand more static variables :

I'll conclude this part by talking about the benefits of such a function : Indeed, now that I can consistantly return the next line of a desired file, I can use it for example in a game project where GNL will help me read my map files and parse it correctly. So did I in so_long and cub3d graphic projects. Moreover, making this function helped me understand even more how to work with strings, files, and read function.