How to read from a file.csv and save every value in a string of array C

Question

I have a file with 6.321.078 records, they are formed by couple of integers separated by a comma. My aim is to read line by line and save it inside a char array (so, strings). My trouble is , when I run sscanf() it doesn't work. I think that this is the problem but I'm not sure that is the only one. I know that the file contain INT, but I need to save every line such as string. What can I do and why does not it work? (There is an example of my file.csv below)

main.c:

int main() {
    FILE *fd;
    char *arr;
    arr = (char *)malloc(6321078);
    for (int k = 0; k < 6321078; k++) {
        arr[k] = calloc(20, sizeof(char));
    }
    char *r;
    int pos = 0;
    int n;
    fd = fopen("file.csv", "r");
    if (fd == NULL) {
       perror("Error");
       exit(1);
    }

    while (fgets(r, sizeof(r), fd) != NULL) {
        sscanf(r, "%s", arr[pos]);
        printf("%s", arr[pos]);
        pos++;
    }
}

Example of file.csv:

I really can't unravel what the code is supposed to do. arr[k] = calloc(20, sizeof(char)); that doesn't make sense as arr has not been allocated as an array of char * but rather an array of char. char *r; fgets(r,sizeof(r),fd) that is undefined behaviour as r is an unintialised pointer. And sizeof(r) will give just the size of a single pointer. — kaylum
– kaylum, Commented Nov 23, 2020 at 11:12
I want to create an array that contain strings with size 20. So how can I do this? @kaylum — cocoricò
– cocoricò, Commented Nov 23, 2020 at 11:18

user3121023 · Accepted Answer · 2020-11-23 13:02:22Z

1

A pointer to array of 20 could be used char (*arr)[20]
Then allocate memory for the number of records.
Use fgets to read directly from the file into each record.
When done, close the file and free the memory.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define SIZE 6321078
#define LEN 20

int main ( void) {
    char (*arr)[LEN] = NULL;
    int pos = 0;
    FILE *fd = NULL;

    if ( NULL == ( fd = fopen("file.csv", "r"))) {
        perror("Error");
        exit ( EXIT_FAILURE);
    }

    if ( NULL == ( arr = calloc ( SIZE, sizeof *arr))) {
        fclose ( fd);
        fprintf ( stderr, "calloc problem\n");
        exit ( EXIT_FAILURE);
    }

    while ( pos < SIZE && fgets ( arr[pos], sizeof arr[pos], fd)) {
        printf ( "%s", arr[pos]);
        ++pos;
    }

    fclose ( fd);
    free ( arr);

    return 0;
}

answered Nov 23, 2020 at 13:02

user3121023

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