Get Next Line (GNL) 🚜

The aim of this project is to make you code a function that returns a line ending with a newline, read from a file descriptor.

This project will not only allow you to add a very convenient function to your collection, but it will also allow you to learn a highly interesting new concept in C programming: "static variables"

Function Prototype

int	get_next_line(int fd, char **line);

Compilation

GNL Mandatory Part

Your program must compile with the flag -D BUFFER_SIZE=xx. which will be used as the buffer size for the read calls in your get_next_line.

Make sure that your function behaves well when it reads from a file and when it reads from the standard input.

👉 Locate in the 42-silicon-valley-libft folder.

GNL with files

gcc tests/main.c -Wall -Wextra -Werror -D BUFFER_SIZE=32 get_next_line.c get_next_line_utils.c

./a.out tests/files/part1_test01_with_lines

GNL with standard input (stdin)

gcc tests/main_stdin.c -Wall -Wextra -Werror -D BUFFER_SIZE=32 get_next_line.c get_next_line_utils.c

./a.out

GNL Bonus Part

gcc tests/main_bonus.c -g -Wall -Wextra -Werror -D BUFFER_SIZE=1 get_next_line_bonus.c get_next_line_utils_bonus.c

./a.out

Points to understand in GNL

According to our GNL subject Calling your function get_next_line in a loop will then allow you to read the text available on a file descriptor one line at a time until the EOF

Call GNL from the main

int main(int argc, char **argv)
{
	int fd, ret, line_count;
	char *line;

	line_count = 1;
	ret = 0;
	line = NULL;
	if (argc == 2)
	{
		fd = open(argv[1], O_RDONLY);
		while ((ret = get_next_line(fd, &line)) > 0)
		{
			printf(" \n [ Return: %d ] | A line has been read #%d => %s\n", ret, line_count, line);
			line_count++;
			free(line);
		}
		printf(" \n [ Return: %d ] A line has been read #%d: %s\n", ret, line_count++, line);
		printf("\n");
		if (ret == -1)
			printf("-----------\n An error happened\n");
		else if (ret == 0)
		{
			printf("-----------\n EOF has been reached\n");
			free(line);
		}
		close(fd);
	}

This next line will return an integer that will be used as a parameter for the get_next_line function.

fd = open(argv[1], O_RDONLY);

get_next_line function will return an integer that will be taken to evaluate all the lines until the file ends.

Return value

Value	Description
1	A line has been read
0	EOF has been reached
-1	An error happened

READ() function

#include <unistd.h>
ssize_t read(int fd, void *buf, size_t count);

Input parameters:

• int fd file descriptor is an integer and not a file pointer. The file descriptor for stdin is 0
• void buf pointer to buffer to store characters read by the read function
• size_t count maximum number of characters to read

🚥 Note.: a character is equivalent to a 1 byte and a byte is made up of 8 bits therefore a character is made up of 8 bits (1 byte)

We can do something like this to read 20 bytes or 20 characters:

char buffer[20];
read(fd, buffer, 20);

🚥 Note.: remember read() doesn't add '\0' to terminate to make it string (just gives raw buffer).

Functions Used

External Functions

Function	Description
read()	A line has been read
malloc()	EOF has been reached
free()	An error happened

Utility Functions

Function	Description
ft_strnew()	Uses size as the size for a new string product of memalloc, this will return the new string, after assigning '' 0 "as elements of the string.
ft_strchr()	The strchr() function returns a pointer to the first occurrence of the character c in the string s.
ft_strjoin()	Allocates with malloc and returns a new string, which is the result of the concatenation of 's1' and 's2'.
ft_memdel()	A line has been read
ft_strdup()	Returns a pointer to a new string which is a duplicate of the string s.
ft_substr	Allocates with malloc and returns a substring from the string 's'.
ft_strlen	Calculates the length of the string s, excluding the terminating null byte ('\0')

Testers

42TESTERS-GNL

Author: Mazoise

👉 Locate in the 42-silicon-valley-gnl folder

git clone https://github.com/Mazoise/42TESTERS-GNL.git
cd 42TESTERS-GNL
./all_tests.sh
./all_tests_with_bonus.sh

VALGRIND

Installation

sudo apt-get update -y
sudo apt-get install -y valgrind

How to Use?

gcc tests/main.c -g -Wall -Wextra -Werror -D BUFFER_SIZE=32 get_next_line.c get_next_line_utils.c

valgrind --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes ./a.out tests/files/part1_test01_with_lines

ℹ️ know more about valgrind

FSANITIZE

gcc tests/main.c -g3 -fsanitize=address -Wall -Wextra -Werror -D BUFFER_SIZE=32 get_next_line.c get_next_line_utils.c -I 

./a.out tests/files/part1_test01_with_lines

Other testers

GNL_lover from charMstr

gnlkiller from DontBreakAlex

gnlkiller2 from Sherchryst

Debug with lldb and GUI

gcc -g tests/main.c -Wall -Wextra -Werror -D BUFFER_SIZE=1 get_next_line.c get_next_line_utils.c
lldb a.out
b get_next_line
run tests/files/part1_test01_with_lines
gui

🔦 keys to move

• tab : change window
• s : next line
• directional key : variables navigation
• h : help

Norminette

Use and install this repository: Norminette

Run

norminette *.*

Graded by Moulinette

GNL pdf new curriculum

Download from HERE