passing an array of structs from a function to the main program - c

Question

I have a data file of about 2500 lines. Each line contains 5 parameters. I declare a strut out side of a routine.
typedef struct data
{
char date[9];
char time[3];
float price;
float NAV;
float percent_change;
} _data ;
void readfile(int *j, struct data *input);
void readfile(int *j,struct data *input)
I set aside memory to read each line of the file into an array of structs.
input = calloc(days_of_data,sizeof(*input));
for (i = 0; i< days_of_data; i++)
input[i] = *(_data*)calloc(1,sizeof(_data));
and read the file.
while(fgets(line, 75, fp) != NULL)
{
date = strtok(line,",");
strcpy(input[i].date,date);
time = strtok(NULL,",");
strcpy(input[i].time, time);
price = strtok(NULL,",");
input[i].price = atof(price);
NAV = strtok(NULL,",");
input[i].NAV = atof(NAV);
percent_change = strtok(NULL,",");
input[i].percent_change = atof(percent_change);
i--;
}
This works. Now I want to sent the structure to the main program.
int main(int argc, const char * argv[]) {
struct data *input;
readfile(&j, input);
printf("%f\n",input[0].percent_change);
}
This compiles but crashes on the print statement.

Answer 1

You will have to use return value
struct data * readfile(int *j) {
struct data *input;
/* read the data */
return input;
}
int main(int argc, const char * argv[]) {
struct data *input;
input = readfile(&j);
printf("%f\n",input[0].percent_change);
}
or pointer
void readfile(int *j, struct data **input_out) {
struct data *input;
/* read the data */
*input_out = input;
}
int main(int argc, const char * argv[]) {
struct data *input;
readfile(&j, &input);
printf("%f\n",input[0].percent_change);
}
to pass the data to the caller.