How to read string from file and tokenise it into an array?

Question

My question is: How do i read a string that is on multiple lines as one line of string from a file in C? I'm trying to do a binary map and my 1d array is represented as a 2d array. So this is in my "level_1.txt":

//start of file
WIDTH: 4
HEIGHT: 5

11,12,13,14, 
21,22,23,24, 
31,32,33,34,
41,42,43,44,
51,52,53,54,
// eof

and i would like to get the string "11,12,13,14,21,22...."

And this is my code:

int ImportMapDataFromFile(char *fileName, Map *self)
{
    FILE *pFile;
    char* myStr;

    pFile = fopen(fileName, "r");

    // Check if the file exists:
    if(pFile)
    {
        // scanf width and height
        //fscanf(pFile, "%*s %i %*s %i", &self->width, &self->height);
        /*
        // this doesnt work
        fscanf(pFile, "%*s %i %*s %i %s", &self->width, &self->height, &myStr);
        */
        //printf("%i %i", self->width, self->height);

        // initialise the array
        (self->theScreenMap) = (Grid*)malloc(sizeof(Grid) * self->width * self->height);

        // scan the whole remaining file
        /*
            I dont know how to do this. I tried using fscanf and had a look at fgets
            but i cant seem to make it work sorry.
        */


        // tokenise it
        /*
            Pretty sure i have to use strtok right?
            http://www.cplusplus.com/reference/cstring/strtok/
        */

        // close it
        fclose(pFile);
        printf("%s \n", &myStr);

        return TRUE;
    }
    else
    {
        fclose(pFile);
        return FALSE;
    }
}

What i want to do is read the file, get the size from the 1st 2 lines and use those values to create the 1d array. Then once that's done, i want to read the remaining string and assign it to the array. Eg.

theScreenMap[0] = 11; // first element has 1st token
theScreenMap[1] = 12;
theScreenMap[size - 1] = 54; // last element has last token

Thanks to anyone helping me out. But if anyone has a better way of doing this (read from file and init an array to create binary map), then feel free to tell me so. Thanks! :)

score 4 · Accepted Answer · answered Jul 02 '13 at 04:03

This is just a basic implementation of what you want. The end result would read as many lines as 'height', and concatenate them.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXSIZE 1024
#define MAXLINE 256

char mainArray[MAXSIZE];
char line[MAXLINE];

char *strdup(const char *s) {
    char *str = malloc(strlen(s) + 1);
    if(str) { strcpy(str, s); }
    return str;
}

int main(int argc,char* argv[])
{
    int width,height;
    unsigned int i=0;
    unsigned int count=0;
    char **grid;
    FILE *fp = fopen("multiline.txt","r");
    if(!fp) {perror("multiline.txt");return -1;}
    /* Read the width and height */
    fscanf(fp,"WIDTH: %d\n",&width);
    fscanf(fp,"HEIGHT: %d\n",&height);
    printf("Width: %d,\tHeight: %d\n\n",width,height);
    while(!feof(fp))
    {
        fgets(line,MAXLINE,fp);
        strncat(mainArray,line,strlen(line)-1); /* get rid of newline */
        printf("Line:: %s",line);
        printf("MainArray:: %s\n\n",mainArray);
    }
    /* Get the number of elements */
    for(i=0;i<strlen(mainArray);i++)
    {
        if(mainArray[i]==',')
            count++;
    }
    /* Allocate the grid and tokezine */
    grid = malloc(sizeof(grid) * count);
    grid[0] = strdup(strtok(mainArray,","));
    for(i=1;i<count;i++)
    {
        grid[i] = strdup(strtok(NULL,","));
    }
    /* Display */
    for(i=0;i<count;i++)
    {
        printf("grid[%2d]:: %s\n",i,grid[i]);
        free(grid[i]); /* free the malloc-ed string */
    }
    free(grid);
    fclose(fp);
    return 0;
}

Output for your sample:

Width: 4,   Height: 5

Line:: 11,12,13,14, MainArray:: 11,12,13,14,

Line:: 21,22,23,24, MainArray:: 11,12,13,14,21,22,23,24,

Line:: 31,32,33,34, MainArray:: 11,12,13,14,21,22,23,24,31,32,33,34,

Line:: 41,42,43,44, MainArray::
11,12,13,14,21,22,23,24,31,32,33,34,41,42,43,44,

Line:: 51,52,53,54, MainArray::
11,12,13,14,21,22,23,24,31,32,33,34,41,42,43,44,51,52,53,54,

Line:: 51,52,53,54, MainArray::
11,12,13,14,21,22,23,24,31,32,33,34,41,42,43,44,51,52,53,54,51,52,53,54,

grid [ 0]:: 11
grid [ 1]:: 12
grid [ 2]:: 13
grid [ 3]:: 14
grid [ 4]:: 21
grid [ 5]:: 22
grid [ 6]:: 23
grid [ 7]:: 24
grid [ 8]:: 31
grid [ 9]:: 32
grid [10]:: 33
grid [11]:: 34
grid [12]:: 41
grid [13]:: 42
grid [14]:: 43
grid [15]:: 44
grid [16]:: 51
grid [17]:: 52
grid [18]:: 53
grid [19]:: 54
grid [20]:: 51
grid [21]:: 52
grid [22]:: 53
grid [23]:: 54

That's weird I could've sworn I already commented on this post. Well anyway... Hello Binayaka! Thanks for the help. It works a treat :D — mh4, Jul 04 '13 at 02:14
But i have a question though @BinayaChakraborty . Why do you use strdup? Whats the difference between that and strcpy? I tried to understand by researching abt it but i cant really grasp the "why" though (if that makes sense). // this are the ones that make more sense to me than the rest. [link](http://stackoverflow.com/questions/252782/strdup-what-does-it-do-in-c) [link](http://stackoverflow.com/questions/4079850/why-do-we-need-strdup) I understand that it will return a char pointer to a new "string", which is a duplicate of the "string" pointed to the 's' (the argument) but why? — mh4, Jul 04 '13 at 04:13
@mh4: Think about the scope. If you wanted to use the string pointer afterwards, using a valid return address is necessary. Otherwise, it may SEGFAULT — Binayaka Chakraborty, Jul 04 '13 at 05:27

How to read string from file and tokenise it into an array?

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