Parsing a tab delimited text file in C - c

Question

so, i saw an older post that showed how to do this, but for some reason it seems it no longer works, my input file consists of a header row, and then 15 rows of input, each with 5 columns, first 2 are strings, the last 3 are ints, i have a struct to store them, and im trying to write the contents into an array of these structs
FName LName Credits Transactions Modifer
John Doe 83000 2 1
Jane Doe 64000 5 3
I tried
struct customer cust = { NULL,NULL,0,0,0};
char line[SIZE] = { 0 }, * ptr = NULL;
cust.fName = malloc(15);
cust.lName = malloc(15);
printf("%d\n", &fp);
if (NULL == (fp = fopen("../customers.txt", "r")))
{
perror("Error while opening the file.\n");
exit(EXIT_FAILURE);
}
while (EOF != fscanf(fp, "%s", line))
{
ptr = strtok(line, "\\");
cust.fName = ptr;
printf("%s", ptr);
while (EOF != (ptr = strtok(NULL, "\\")))
{
i++;
printf("%s",ptr);
if (i == 1)
cust.lName = ptr;
else if (i == 2)
cust.miles = atoi(ptr);
else if (i == 3)
cust.years = atoi(ptr);
else if (i == 4)
cust.sequence = atoi(ptr);
}
i = 0;
printf("After Reading: fName:[%s] lName:[%s] miles:[%d] years:[%d]\n", cust.fName, cust.lName, cust.miles, cust.years);
}
For some reason, the printf within the inner while loop only prints "(null)", and errors out when i==2
with the error
File: minkernel\crts\ucrt\inc\corecrt_internal_strtox.h
Line: 1772
Expression: _p != nullptr
I dont have any idea what that error message means, so i dont know what im doing wrong

Answer 1

Also, Craig, do you mind giving an example, im pretty new to using C and am unfamiliar with fgets
Okay. Because your code was a bit far off, I had to refactor it heavily.
Your code was only handling a single customer record. What you need to do is a separate struct instance for each line (i.e. customer). So, we want to use realloc to enlarge a dynamic array of our struct customer.
And, you have allocate memory [on the heap] for each string in a record (i.e. first and last names). So, we have to use strdup
Anyway, here's the code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct customer {
char *fName;
char *lName;
int miles;
int years;
int sequence;
};
int
main(void)
{
FILE *fp;
char buf[1000];
char *cp;
char *bp;
struct customer *list = NULL;
int custcnt = 0;
struct customer *cust;
const char *delim = "\t\n";
int field;
fp = fopen("customers.txt","r");
if (fp == NULL) {
perror("error opening file");
exit(1);
}
while (1) {
cp = fgets(buf,sizeof(buf),fp);
if (cp == NULL)
break;
// increase size of customer list/array by one
list = realloc(list,sizeof(*list) * (custcnt + 1));
if (list == NULL) {
perror("malloc");
exit(1);
}
// point to place for next customer
cust = &list[custcnt];
// advance customer count
++custcnt;
// preclear the new record in case of a line that is malformed (i.e.
// missing some data)
memset(cust,0,sizeof(*cust));
// loop through and store all customer record fields
bp = buf;
for (field = 0; field < 5; ++field) {
cp = strtok(bp,delim);
if (cp == NULL)
break;
bp = NULL;
switch (field) {
case 0:
cust->fName = strdup(cp);
break;
case 1:
cust->lName = strdup(cp);
break;
case 2:
cust->miles = atoi(cp);
break;
case 3:
cust->years = atoi(cp);
break;
case 4:
cust->sequence = atoi(cp);
break;
}
}
printf("After Reading: fName:[%s] lName:[%s] miles:[%d] years:[%d]\n",
cust->fName, cust->lName, cust->miles, cust->years);
}
fclose(fp);
return 0;
}