Thread: Problem with passing structure array to function prototype

Sorry to bother you all again. You all seem like experts next to me, so I thought I'd pick your brains. I'm fairly clueless when it comes to pointers, and I'm sure I've made quite a few rookie mistakes. I'm facing 3 problems with this code:

1. First and foremost, it doesn't appear that I'm correctly passing or referencing the pointers. The read_student printf is returning gibberish, and the main printf is returning even worse gibberish.

2. The call to read_student only seems to work on the first loop. After that, neither of the printfs in read_student print on each loop.

3. The read_student printf counter is initially printing 50 times, yet there is only 25 lines of text to read. There's only a single '\n' at the end of each line. This suggests that the fgets is reading 50 lines, but I don't see how.

Code:

#include <stdio.h>
#include <string.h>

#define STUDENT_FILE "student.txt"

FILE *textin;

int highestMark, counter, lineCounter, nullCounter, i, j;
char line[64];

struct student {
	char id[9];
	int paperOne;
	int paperTwo;
	int paperThree;
	int paperFour;
	int paperFive;
	int paperSix;
	int paperSeven;
	int paperEight;
};

void read_student(struct student *);
void print_student(struct student *);
void copy(int *x, char *y, char *z);

int main() {
	textin = fopen(STUDENT_FILE, "r");
	struct student grades[25];
	lineCounter = 0;
	for (i=0; i<25; i++) {
		read_student(&grades[i]);
	/*	printf("%s\n", grades[i].id);
		print_student(*pGrades[i]); */
		printf("Main counter: %i\n", lineCounter);  /* for testing */
		printf("Printf main: %s\n", grades[i].id);	/* for testing */
		lineCounter++;
		rewind(textin);
	}
	fclose(textin);
}

void read_student(struct student *grades) {
	counter = 0;
	while (fgets(line, 65, textin) != NULL) {
		if (counter == lineCounter) {
			sscanf(line, "%s %d %d %d %d %d %d %d %d", grades->id, &grades->paperOne, &grades->paperTwo, 
			&grades->paperThree, &grades->paperFour, &grades->paperFive, &grades->paperSix, &grades->paperSeven, 
			&grades->paperEight);
		}
		if (line[0] != '\n') {
			counter++;
		}
	}
}

EDIT: Solved problem 2 by placing a rewind(textin) in the main loop.

EDIT2: Solved. I had to add a check for the return character '\n' on its own line. fgets was reading end of line at \r, then promptly reading end of line again at the \n. I've uploaded the fix and the current build in case anyone else gets stuck in a similar situation. Thanks to everyone who lent a hand.

Thanks Tater.

For copying the array of int, do you mean another function prototype? Something like:

Code:

edited:
void copy(int *x, char *y, char *z) {
	tempInt = *y - 48;
	tempIntTwo = *z - 48;
	*x = tempChar + tempCharTwo;
}

As for using sscanf, I've removed the 8 count loop, and replaced it with:

Code:

sscanf(line, "%s", grades->id);

Haha, yes. I've been stuck into array and pointer tutorials for about a day now, but some of it is lost on me.

Here is the file I'm trying to read:

Code:

41018467     74     80     69     44     58     58     62     84
05028145     41     67     41     51     95     42     67     76
91014604     42     73     92     62     61     96     78     75
47021726     51     58     49     92     87     59     95     94
03023811     42     73     73     84     61     71     93     68
47027644     62     97     97     59     63     61     89     94
16003035     90     82     88     86     80     42     44     68
46023805     90     49     50     90     46     61     73     48
29012623     64     74     76     60     86     96     51     68
44032439     66     83     57     93     78     82     49     81
33031115     59     58     64     70     97     66     93     46
21028745     84     92     70     49     57     73     97     52
86013290     81     76     75     87     55     74     51     92
50001150     61     44     86     50     67     51     47     97
57012287     73     43     45     69     89     78     81     88
22024946     66     50     73     48     40     51     82     75
10006359     64     57     48     43     95     61     42     90
91030836     54     80     76     61     88     79     88     44
81004734     93     59     58     78     40     48     47     87
28014893     88     83     87     61     70     57     53     74
09007616     75     91     60     69     59     96     95     43
24011008     64     69     89     42     55     65     73     43
23001587     74     63     48     40     58     58     40     96
98015281     69     78     89     77     52     82     96     98
38024179     50     57     78     51     55     68     56     91

Ok... not being certain what each column represents you could do something like this...

Code:

struct tStudents
  { int id;
     int mark[8];
   } student[100];


idx = 0;
while (fgets(line, 64, textin) != NULL) {
  sscanf(" %d %d %d %d %d %d %d %d %d", student[idx].id,
                 student[idx].mark[0],student[idx].mark[1],student[idx].mark[2],student[idx].mark[3],
                 student[idx].mark[4],student[idx].mark[5],student[idx].mark[6],student[idx].mark[7]);	
   ++idx; 
}

A complication may come if those are tabs instead of spaces between columns... then it becomes sscanf("%d\t%d\t...
Also if the array gets too big, or you have an unknown number of students you may need to typedef the struct and use malloc() and realloc() to get the space you need.

Thanks very much, Tater. I've implemented your sscanf suggestion (edit in first post) and it's actually passing the data back to int main() now. Unfortunately I still have to use the void function, as it's part of the requested specifications. I'm still having problems with the function returning gibberish, but only on every second loop.