Reading a csv file using C and then doing string manipulation - c

Question

First I open a CSV file (Cars.csv) using my C file cars.c. My CSV file would look like:
toyota, 100, 20, 150.50
nissan, 200, 50, 100.75
BMW, 400, 80, 323.00
The 1st column is names, 2nd column is stock, 3rd column is order, 4th column is price.
Then I have to do two works(I will call the program in the commandline with the work name and any other argument I need to pass):
List all the items in the CSV file while the commas cannot be a part of the output. I also have to print headers for each column. (./cars list)
I would send an argument when running the program from the command line. The argument would be one the name of the items in my csv file. Then I would have to subtract 1 from the stock and update the CSVfile. (./cars reduce nissan)
This is how I opened the CSV file.
void main(int argc, char *argv[]) {
FILE *in = fopen ("Cars.csv" ,"rt");
if (in == NULL) {
fclose (in); return 0;
}
//I need to store the data from the CSV file in an array of pointers. I know how to do that, but Im having a problem in storing them without the commas and then doing what I need to do in part 1.
//This is the only code I could write for the 2nd part.
int p =0;
for(p =0; p<; p = p + 4) {
if(strcmp(argsv[2],save[p]) == 0) { //save is the array of pointers where I
int r = int(save[p +1]); //store the data from the csv file
int s = r - 1;
char str[15];
sprintf(str, "%d", s);
save[p +1] = str; // not sure if this line actually makes sense
}
}

Answer 1

There are a couple of possible solutions.
Here's one:
Read the lines into an array of pointers. Allocate array with malloc and reallocate as needed with realloc. Read lines with fgets.
For each line, use strtok to split the line, and do whatever you need with each field.
Another solution:
Use your favorite search engine to search for an existing CSV-reading library (there are many out there, which can handle very advanced CSV files).

Answer 2

Think how the data should be represented and define a structure.
typedef struct {
char *name;
int stock;
int order;
double price;
} car_type;
Open the file: See OP's code
Find how many lines and allocate memory
char buf[100];
size_t n = 0;
while (fgets(buf, sizeof buf, in) != NULL) n++;
rewind(in);
car_type *car = malloc(n * sizeof *car);
if (car == NULL) OutOfMemory();
Read the cars
for (size_t i=0; i<n; i++) {
if (fgets(buf, sizeof buf, in) == NULL) Handle_UnexpectedEOF();
char car_name[100];
if (4 != sscanf(buf, "%s ,%d ,%d, %lf", car_name,
&car[i].stock, &car[i].order, &car[i].price) Handle_FormatError();
car[i].name = strdup(car_name);
}
// Use `car` ...
When done
fclose(in);
for (size_t i=0; i<n; i++) {
free(car[i].name);
}
free(car);