GNL

GET NEXT LINE

"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."

🚀 Contents

🚩 Mandatory part

Title	Description
Function name	get_next_line
Prototype	int get_next_line(int fd, char **line);
Turn in files	get_next_line.c, get_next_line_utils.c, get_next_line.h
Parameters	#1. file descriptor for reading #2. The value of what has been read
Return value	1 : A line has been read 0 : EOF has been reached -1 : An error happened
External functs.	read, malloc, free
Description	Write a function which returns a line read from a file descriptor, without the newline.

• 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.
• Make sure that your function behaves well when it reads from a file and when it reads from the standard input.
• libft is not allowed for this project. You must add a get_next_line_utils.c file which will contain the functions that are needed for your get_next_line to work.
• 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. This value will be modified by your evaluators and by moulinette.
• Compilation will be done this way : gcc -Wall -Wextra -Werror -D BUFFER_SIZE=32 get_next_line.c get_next_line_utils.c
• Your read must use the BUFFER_SIZE defined during compilation to read from a file or from stdin.
• In the header file get_next_line.h you must have at least the prototype of the function get_next_line.
• We consider that get_next_line has an undefined behavior if, between two calls, the same file descriptor switches to a different file before EOF has been reached on the first fd.
• lseek is not an allowed function. File reading must be done only once.
• Finally we consider that get_next_line has an undefined behavior when reading from a binary file. However, if you wish, you can make this behavior coherent.
• Global variables are forbidden.

🚩 Bonus part

The project get_next_line is straightforward and leaves very little room for bonuses, but I am sure that you have a lot of imagination. If you aced perfectly the mandatory part, then by all means complete this bonus part to go further. I repeat, no bonus will be taken into consideration if the mandatory part isn’t perfect. Turn-in all 3 initial files with _bonus for this part.

• To succeed get_next_line with a single static variable.
• To be able to manage multiple file descriptor with your get_next_line. For example, if the file descriptors 3, 4 and 5 are accessible for reading, then you can call get_next_line once on 3, once on 4, once again on 3 then once on 5 etc. without losing the reading thread on each of the descriptors.

⭐ Key points

• Key concept: buffer static variables

• 어떠한 파일을 받아와서 '\n'을 기준으로 한 줄씩 가져오는 함수를 만드는 과제

• 컴파일 과정에서 버퍼 사이즈를 입력 받는다.

• gcc -D defines a macro to be used by the preprocessor.

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

• main 에서 open() 함수를 이용하여 파일을 열어 파일 디스크립터를 gnl 에 넘겨준다.

  fd = open("test.txt", O_RDONLY);
  

• 여러 파일 디스크립터도 다룰 수 있기 위해서는 static char *backup[MAX_FD] 처럼 포인터 배열을 사용한다.

• 처음 시도에는 char *buf[BUFFER_SIZE + 1] 로 배열을 선언하였지만,

• BUFFER_SIZE 가 아주 커지는 경우 SEG FAULT 가 발생하는 문제로 인해 malloc() 을 통해 메모리를 할당하는 것으로 변경하였다.

⭐ Reference

🔗 hidaehyunlee's Github
🔗 배경지식 정리
🔗 Overview
🔗 테스터 참고
🔗 GNL 과제 수행 전 알아야할 내용
🔗 참고자료 모음