get_next_line

What is GNL?

• get_next_line()(GNL) is a program that is able to read from a textfile and display each line ending with a newline character. This this project done with only using read(), malloc(),free() and our own library libft we build previously.
• Project done at WeThinkCode JHB campus (based on 42 france coding curriculum)

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• More info on WeThinkCode: https://www.wethinkcode.co.za/
• More info on 42 school(US based school English site): https://www.42.us.org/
• More info on 42 school(France based school French site): https://www.42.fr/

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Table of contents

1. Requirements of the project
2. How it works
3. Installation
4. How to run GNL

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Language used

• C

Requirements of the project:

• Create a function that returns a line read from a file descriptor
• The following prototype must be used:

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

fd = file descriptor used | line = the pointer used to store line read

• Your function get_next_line() must return its result without \n
• To get a full project outline, please refer to the pdf

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How it works

The main goal of the project is to replicate the function fgets() to read a line from a texfile similar to the example code.

//EXAMPLE CODE
int main(int argc,char **argv)
{
        FILE * x;
        x=fopen("myfile.txt","r");
        char hold[256]; // Step 2
        while(fgets(hold,sizeof(hold),x) != NULL) // Step 1 +2
        {
                printf("%s",hold); // Step 3
        }
        fclose(x);
        return (0);
}

fgets() is function that reads a line from a stream (e.g the mytextfile.txt in this case) at "x" number of characters at a time (i.e size of string or BUFF_SIZE).On success, the function returns a line which is indentified by the \n representing end of a line.The line is stored in a variable with a allocated size(i.e hold with length of 256).When it reaches the 'End of File(EOF)' indicated by \0 it simply returns NULL.

char *fgets(char *str, int n, FILE *stream)

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How to create fget()

To replicate fget() GNL is broken down into the following steps:

Step1. In main.py, the called function get_next_line() is used read each line until EOF which returns a value of -1

while ((x = get_next_line(fd, &line2)) > 0)

Step2. In get_next_line.c the function get_next_line() copies characters from file descriptor into a pointer called tempaccording to BUFF_SIZE found in get_next_line.h Here is an example for how it would work :

1. If the BUFF_SIZE = 3

    line = "Hi\nMy name is Nathi"
    s1=[H][i][\n](first loop)

• If no nextline character is found, the function get_next_line() keeps reading new characters and concatenates them with temp
• If the nextline character is found the function ft_cpy()is used to create a new temp variable without the \n and returned to ft_leftover.
• ft_leftover() is used to create new pointer,allocate memory for pointer and return pointer without nextline.
• Lastly, the final line 'Hi' is returned in line2.

Step3. In main.py get_next_line() returns line2 to display all lines in textfile with \n added at the end

while ((x = get_next_line(fd, &line2)) > 0)
{
	ft_putstr(line2); // function from libft to display string to standard output
	ft_putchar('\n'); // function from libft to display char to standard output
	free(line2);
}

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Installation

1. git clone repo
2. Enter /get_next_line folder
3. git clone libft
4. Enter /libft folder
5. To compile Makefile of libft type:

make re

6. Go back to /get_next_line folder
7. To compile Makefile of get_next_line type:

make all

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How to run get_next_line

1. To execute file type:

./run.a mytext.txt

You should see

aaa
bbb
ccc

displayed to standard output from myfile.txt

Makefile commands

• make re - recompile library when changes are made to functions
• make clean - removes all function objects
• make fclean - removes all function objects created with library object