get_next_line

This project is about implementing a function in C that reads a file line by line using a file descriptor. The function reads one line per call and preserves the input between calls using a static buffer. Our challanges were handling error management, memory allocation, static variables and buffer management efficiently in C.

🧠 Core Functionality

• Reads one line including the newline \n
• Works with different BUFFER_SIZEvalues
• Returns NULL if no more lines to read or on error
• Handles different file descriptors (stdin, file descriptor, ...)
• Manages memory safely between successive calls

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📁 File Structure

get_next_line.c

Contains the main logic. The function reads from the file descriptor and returns one line at a time.

get_next_line_utilis.c

Contains all the necessary helper functions (string operations, memory handling, etc.).

get_next_line.h

Header file that declares the function prototype and any required includes/macros.

🔧 Main Function

get_next_line()

Validates a file descriptor and returns the next full line (including a new line if it occurs).

Parameters:

• int fd: File descriptor to read from file

Returns:

• NULL if:
  • End-of-file is reached
  • An error occurs (e.g., invalid fd, read failure, or memory allocation error)
• a dynamically allocated string containing the next line (including \n if it exists)

🔧🔧 Helper Functions

buffer_check()

Determines the end of a line, appends buffer content to the current line with the function new_line() and shifts remaining content with the function buffer_change() for future calls.

Parameters:

• char *buffer: Buffer containing the input from fd
• char *line: A dynamically allocated string containing the next line (including \n if it exists)

Returns:

• line with \n

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new_line()

Appends one element from the buffer content to the current line.

Parameters:

• char *line: the next line
• char c: one element from the buffer

Returns:

• line with one char from buffer

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change_buffer()

Shifts remaining content for future calls.

Parameters:

• char *buffer: old buffer
• size_t start: starting index of new buffer from old buffer

Returns:

• shifted buffer

Other Functions

Function Name	Category	Parameters	Return
ft_strlen	String Utility	const char *s	Length of the string (size_t)
free_mem	Memory/Error Handling	char *line, int bytesRead	Always returns NULL (after free line)

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🛠️ Compilation

Compile the source files:

cc *.c -o get_next_line

Then you can execute like:

./get_next_line

💡 Example Usage

You can use get_next_line in your source file.

#include <stdio.h>
#include <fcntl.h>
#include "get_next_line.h"

int	main(void)
{
	int fd = open("test", O_RDONLY);
	char *line;
	line = get_next_line(fd);
	printf("1.line: %s", line);
	free(line);
	line = get_next_line(fd);
	printf("2.line: %s", line);
	free(line);
	line = get_next_line(fd);
	printf("3.line: %s", line);
	free(line);
	close(fd);
	return (1);
}

🔎 Testing

-different BUFFER_SIZE values -no filedescriptor