Using fgets and sscanf for taking a string from a file - c

Question

i have a file.txt structured this way:
author, "title", genre, price, copies_inStock
R. Tolkien, "The lords of the rings", Fantasy, 65.50, 31
i tried using fgets and sscanf
FILE *fp = NULL;
char string[100];
char title[30], author[30], genre[30];
float price;
int copies=0;
fp = fopen("text.txt", "r");
while(!feof(fp)) {
fgets(string, 100, fp);
sscanf(string, "%[^,],%[^,],%[^,],%f[^,],%d[^ ]", autore, titolo, genere, &prezzo, &copie);
}
fclose(fp);
printf("%s %s %s %.2f %d\n", author, title, genre, price, copies);
OUTPUT
R. Tolkien "The lord of the rings" fantasy 65,50 0
Why it don't access to the variable copies?
There are better ways? Thanks

Answer 1

The format specifiers on this line are incorrect
sscanf(string, "%[^,],%[^,],%[^,],%f[^,],%d[^ ]", autore, titolo, genere, &prezzo, &copie);
It should be
sscanf(string, "%[^,], %[^,], %[^,],%f,%d", autore, titolo, genere, &prezzo, &copie);
The additional spaces are to filter leading whitespace - it is not automatic with %[] (or with %c).
The %f and %d were a sort of mangled hybrid of what they should be. The conversion of those stops at the first character that cannot be used, without your intervention.
Side note: you really must check the result of scanf() function family: the number of successful conversions made.

Answer 2

"%f[^,]" is legal, yet certainly not what OP wants.
"%f" scans for a float, then "[^,]" scans for that 4 character sequence.
There are better ways?
Use " %n" to check scanning success. It records the offset of the scan.
Use width limits like 29 in %29[^,] to not overfill the char array.
Use a space before %29[^,] to consume optional leading whitespace.
Money is always tricky.
Do not use while(!feof(fp)). Check return from fgets().
char string[100];
char title[30], author[30], genre[30];
double price;
int copies;
FILE *fp = fopen("text.txt", "r");
if (fp) {
while(fgets(string, sizeof string, fp)) {
int n = 0;
sscanf(string, " %29[^,], %29[^,], %29[^,],%lf ,%d %n",
author, title, genre, &price, &copies, &n);
// If n==0, scan was incomplete
// If string[n], string has extra garbage
if (n == 0 || string[n]) {
fprintf(stderr, "Bad <%s>\n", string);
} else {
printf("%s %s %s %.2f %d\n", author, title, genre, price, copies);
// Robust code here would do additional work:
// Trim trailing string whitespace. Range checks on numeric values, etc.
}
}
fclose(fp);
}