Function to read an file.

Hi,
I have to write a programm that reads a text (*.txt) one line a time and stores every line up to MAXLINE characters in a char line[ ***] table and returns a pointer to the first character of the line or NULL if there are no more lines. So I have written the functions ( there have to be some addons and corrections), and the programm, it all gets compiled but I get an segmentation error at the start of the function where everything schould be ok!
here the main()- without some code that has to do with the computer-user dialog:

Code:

#include <stdio.h>
#define MAXLINE 128
#define MAXIMUMLINES 500

struct node {
        char         *line;
        struct node  *prev;
        struct node  *next;
};

struct list {
        struct node  *head;
        struct node  *tail;
        int           size;
        int     currentpos;
        char      *current;
};

void ReadFile(struct list *buffer, char *filename);
void WriteFile(struct list *buffer, char *filename);
void PrintLine(struct list *buffer);
void GoToLine(struct list *buffer, int lineNumber);
void DeleteLine(struct list *buffer);
void InsertBefore(struct list *buffer, char *newline);
void InsertAfter(struct list *buffer, char *newline);

main()
{

char *filename; 
struct list *buffer = malloc(sizeof (struct list));             
buffer->head = 0;
buffer->tail = 0;
buffer->size = 0;
buffer->currentpos = 0;
buffer->current = 0;

scanf("%s", &filename);
                ReadFile(buffer, filename);
}               


/*And here the FUNCTION:                      */

void ReadFile(struct list *buffer, char *filename)
{
        char *currentpos;
        char line[MAXLINE];
        int a, j;
        char *s;

                FILE *fp;
                fp=fopen("*filename","r");           // <-----Untill here everything works.                             
                                                                      //Then the segmentation fault appears.
                if (fgets(line, MAXLINE, fp)!=NULL);      
            {
                for (j=1; j<=MAXIMUMLINES; ++j)               
                sscanf(line,"%s", line[j]);     
                }
                *currentpos=line[0];
                fclose(fp);
}

Whats the mistake. I think it must be something with pointers again, but cant find it.

remove the '&' from the scanf. With scanf you don't take the address when arg 2 is an array. Also in the fopen remove the double quotes and '*' from filename. You need to add something like:

Code:

if (fp == NULL) printf("Can't open %s\n", filename);

to handle errors.

You also have allocation problems in your list. You need code to allocate a node for each line and set the next/previous pointers each time through. To be clear, you only need one struct list, but you need a node for each line. Take a look at some linked list example code for more help.

-Rog

Your fopen line should be:

Code:

fp = fopen(filename, "r");

and not

Code:

fp = fopen("*filename", "r");

Thank you!
It now looks much-much better.
Now I will allocate the node for each line!

I have problems to allocate the data....
I think ist very complicated for a newby like me.
So, I want to use a struct node, where very line is a node,
and a struct list.
here the function again with some changes:

Code:

void ReadFile(struct list *buffer, char *filename)
{
        int currentpos, size;
        char line[MAXLINE];
        int a, j;
        char *s[size];

                size=0;                                                     //isos fygei!

                FILE *fp;
                fp=fopen(filename,"r");
                if (fp==NULL)
                        printf("File %s can't be read!", filename);
                else
                {       while ((fgets(line, MAXLINE, fp))!=NULL);
                        {
                            /*PLACE (1)*/
                        }
                }
}

so, I have 3 questions:
1.What whil I have to insert to PLACE(1) so that the programm stores the text, each line a node pointing to the next line?
2. Have I to add something in main?
---------------------------------------------------------------------------------
3.(has nothing to do with the other questions, maybe I should post a new thread) I have a programm in C which defines MALLOC ALLOC etc, as better versions of malloc alloc etc. Where in my linux system schould I put it or the .out programm so that I can use MALLOC in my programm instead of malloc?