C parsing fgets() char array into multiple variables with sscanf using structures - c

Question

In this program it compiles but i get segmentation fault, sscanf(str, "%d %s %s %d %f", &pos, z[pos-1].city, z[pos-1].state, &z[pos-1].population, &z[pos-1].growth); its because this line z[pos-1].city, z[pos-1].state, doesnt have & but when i add that i get warning: format â%sâ expects type âchar *â, but argument 4 has type âchar (*)[200]â.
i'm sure there is another way of doing this, i need to use structure, read in file store info into an array of a structure then displaying the array. the printf works just storing the city and state into char array.
I commented the area where i tried to initialize to array and had an incompatable type with the char array value all three: a, 'a', "a".
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct{
int rank;
char city[200];
char state[50];
int population;
float growth;
}city_t;
void read_data(city_t *z)
{
FILE *inp;
inp = fopen("cities.dat", "r");
char str[256];
int pos = 0;
if(inp==NULL)
{
printf("The input file does not exist\n");
}
else
{
/*reads and test until eof*/
while(1)
{
/*if EOF break while loop*/
if(feof(inp))
{break;}
else
{
/*read in a number into testNum*/
//fscanf(inp, "%d", &testNum);
fgets(str,sizeof(str),inp);
sscanf(str, "%d %s %s %d %f", &pos, z[pos-1].city, z[pos-1].state, &z[pos-1].population, &z[pos-1].growth);
z[pos-1].rank = pos;
}
}
}
fclose(inp);
}
void print_data(city_t *z, int size)
{
int i;
printf("rank\tcity\t\tstate\tpopulation\t\tgrowth\n");
for(i=0;i<size;i++)
{
printf("%d\t%s\t\t%s\t\%d\t\t%f\n", z[i].rank, z[i].city, z[i].state, z[i].population, z[i].growth);
}
}
int main()
{
int i;
city_t cities[10];
/*for(i;i<10;i++)
{
cities[i].rank = 0;
cities[i].city = "a";
cities[i].state = "a";
cities[i].population = 0;
cities[i].growth = 0.00;
}*/
read_data(&cities[0]);
print_data(&cities[0], 10);
return(0);
}
{
dat file
1 New_York NY 8143197 9.4
2 Los_Angeles CA 3844829 6.0
3 Chicago IL 2842518 4.0
4 Houston TX 2016582 19.8
5 Philadelphia PA 1463281 -4.3
6 Phoenix AZ 1461575 34.3
7 San_Antonio TX 1256509 22.3
8 San_Diego CA 1255540 10.2
9 Dallas TX 1213825 18.0
10 San_Jose CA 912332 14.4
}

Answer 1

In read_data, you scan into z[pos-1].... where pos starts at 0. So you will be writing beyond (before) the extend of the array.
Just do a global replace of pos-1 with pos and also increment pos; you can also use fscanf, so your reading can be:
for (int pos=0; !feof(inp); ++pos)
{
fscanf(inp, "%d %s %s %d %f",
&z[pos].rank,
z[pos].city,
z[pos].state,
&z[pos].population,
&z[pos].growth);
}