Reading .csv file into an array in C

Question

I am Currently trying to read a .csv file into an array in C. I'm somewhat on the fence on how to approach the problem. I've looked through many forums and related topic but I still can't grasp it. If someone could show me or break it down as simple as possible. That would be greatly appreciated. By the way, the contents of the .csv file is like this. The array should consist of just the alphabet and the number. I was thinking about using a 2-D array. Is that an appropriate solution?

A,1
B,2
C,3
....

Yes it's somewhat a duplicate question, and i did take a look at the forum prior to making this one. I still don't get it. — mac, Jan 23 '17 at 03:20

John Zwinck · Answer 1 · 2017-01-23T05:12:51.990

5

Start by defining your data structure:

struct my_record {
    char name;
    int value;
};

Then you can read like this:

FILE* my_file = fopen(...);
struct my_record records[100];
size_t count = 0;
for (; count < sizeof(records)/sizeof(records[0]); ++count)
{
    int got = fscanf(my_file, "%c,%d", &records[count].name, &records[count].value);
    if (got != 2) break; // wrong number of tokens - maybe end of file
}
fclose(my_file);

Now you have a 1D array of structs, one for each row.

edited Jan 23 '17 at 05:12

answered Jan 23 '17 at 03:22

John Zwinck

239,568
38
324
436

What to do if number of entries in a row varies? – Plutonium smuggler Nov 30 '17 at 11:22
@Plutoniumsmuggler: Then you can store a `std::vector` for each line. – John Zwinck Nov 30 '17 at 11:57
C does not have std::vectors. I meant c not C++ (as the question says) – Plutonium smuggler Dec 14 '17 at 08:21
@Plutoniumsmuggler: Sorry I forgot when replying to your comment. In C you can use whatever dynamic array class you have at hand. If you have none, you might try this one: https://developer.gnome.org/glib/stable/glib-Arrays.html – John Zwinck Dec 14 '17 at 09:20

RoadRunner · Answer 2 · 2017-01-23T04:52:38.960

You can just create an array of structs, as the other answer described.

Once you have the struct definition:

typedef struct {
    char letter;
    int number;
} record_t;

Then you can create an array of structs like this:

record_t records[26]; /* 26 letters in alphabet, can be anything you want */

Using a 2D array would be unnecessary, as wrapping the letter and number in a struct would be easier to handle.

In terms of reading your file, you can just read with fscanf() until 2 values are not found.

Here is some basic code you can use:

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

#define NUMLETTERS 26

typedef struct {
    char letter;
    int number;
} record_t;

int main(void) {
    FILE *fp;
    record_t records[NUMLETTERS];
    size_t count = 0;

    fp = fopen("letters.csv", "r");
    if (fp == NULL) {
        fprintf(stderr, "Error reading file\n");
        return 1;
    }

    while (fscanf(fp, " %c,%d", &records[count].letter, &records[count].number) == 2) {
        count++;
    }

    for (size_t i = 0; i < count; i++) {
        printf("%c,%d\n", records[i].letter, records[i].number);
    }

    fclose(fp);

    return 0;
}

Reading .csv file into an array in C

2 Answers2

Linked