Update csv column in C - c

Question

I have the following code which is supposed to read and write to csv file. I want to add update field functionality so I will be able to search and find certain field cell (this is already implemented) and then update (overwrite) field cell next to it.
csv has following configuration:
| town | rss | soc |
|:--: |:--:|:--:|
| LA | sol | sap |
| BA | kol | kap |
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// parse csv file to next ","
const char *getfield(char *line, int num)
{
const char *tok;
for (tok = strtok(line, ",");
tok && *tok;
tok = strtok(NULL, ",\n"))
{
if (!--num)
return tok;
}
return NULL;
}
int main()
{
char *name;
FILE *fp;
fp = fopen("file.csv", "r+");
int result;
char line[1024];
while (fgets(line, 1024, fp))
{
char *tmp = strdup(line);
getfield(tmp, 1);
// comparing strings str1 and str2
name = "LA";
result = strcmp(name, tmp);
// found required name
if (result == 0)
{
char *tmp2 = strdup(line);
printf("Field 2 would be %s\n", getfield(tmp2, 2));
// this section should overwrite next column cell to POP
fprintf(fp, "POP");
}
free(tmp);
}
}
it should look like this after update
csv has following configuration:
| town | rss | soc |
|:--: |:--:|:--:|
| LA | POP | sap |
| BA | kol | kap |