如何读取 .csv 文件并将其保存到二维数组中？

Question

I am quite new to C programming and I have been set the task of reading a .csv file containing a 2d integer array, I need to then print it so it shows up in the terminal. The array is a 4 row by 2 col integer array, but when I use this code I get a random list of numbers. I have attached the code I used and the .csv file array and how it should look like.

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

int main()
{
    FILE *in_data = fopen("in.csv", "r");
    
    int i;
    int j;
    int trIn[4][2];
    if(in_data == NULL)
    {
        printf("error\n");
        return 1;
    }
    for(i = 0; i < 4; i++){
    for(j = 0; j < 2; j++){
        char junk;

        if (j != 0) fgetc(in_data);

        fscanf(in_data, "%c%d%c", &junk, &trIn[i][j], &junk);
        printf("%d ", trIn[i][j]);
    }
    fgetc(in_data);
    printf("\n");
    }
return 0;
}
    

.csv file array:

0 0
0 1
1 0
1 1

.csv file (raw):

"0","0"
"0","1"
"1","0"
"1","1"

Answer 1

You can create a pattern which discards the unwanted characters, like so:

Live demo

for (i = 0; i < 4; i++)
{
    for (j = 0; j < 2; j++)
    {
        //printf("%s", str); //print str to check if there are any weird chars
        fscanf(in_data, " \"%d\",", &trIn[i][j]);
        printf("%d ", trIn[i][j]);
    }
    printf("\n");
}

Chek if you have spaces in the lines after the values, that can throw fscanf off. Although a space before the specifier, like in the sample, should solve that.

Also, you can export .csv files without the quotation marks, if that's something you can control.

You can also try a more robust method using a combo of fgets and sscanf :

Live demo

char str[20];
int i = 0;
int j = 0;

//...

while (i < 4 && fgets(str, sizeof str, in_data))
{
    //printf("%s", str); //print str to check if there are any weird chars
    if(sscanf(str, "\"%d\",\"%d\"", &trIn[i][j], &trIn[i][j+1]) == 2)
        printf("%d %d\n", trIn[i][j], trIn[i][j+1]);
    i++;
}

Answer 2

You can replace you current loop with this one:

for(i = 0; i < 4; i++){
    for(j = 0; j < 2; j++){
        char junk;

        if (j != 0) fgetc(in_data);

        fscanf(in_data, "%c%d%c", &junk, &trIn[i][j], &junk);
        printf("%d ", trIn[i][j]);
    }
    fgetc(in_data);
    printf("\n");
}

This works because fscanf(in_data, "%d", &trIn[i][j]) reads an int ( %d ) from the file in_data into the memory location of trIn[i][j] . fgetc didn't work because it only reads a single character which was then printed as if it were an integer.

EDIT: Now, for each value in the .csv file, you read to a junk variable the " and \\n characters.

Line by line:

if (j != 0) fgetc(in_data); reads the , from the csv file into a junk variable (which isn't the first character on a line).

fscanf(in_data, "%c%d%c", &junk, &trIn[i][j], &junk); reads:

• 1st: the opening " character into a junk variable
• 2nd: the number (int: %d ) into to memory location of trIn[i][j] .
• 3rd: the closing " character into a junk variable