I have a problem regarding creating dynamic struct arrays. The thing is I read from a file and I am not allowed to initialize the struct after the scanf
. The thing is that I want to create x amounts of structs of the type vinnareinfo. I can add that we are only allowed to use C90 since it's a school project. Would really apreciate all the help out there! :D
#include <stdio.h>
struct vinnareinfo{
char fornamn[20];
char efternamn[20];
int ar;
};
main(){
struct vinnareinfo *vinnare;
int i = 0, x;
FILE *file;
file = fopen("C:\\Uppgifter.txt", "r");
if (file != NULL){
fscanf(file, "%d", &i);
}
else{
printf("Ange antal vinnare:");
scanf("%d", &i);
i = i - 1;
for (x = 0; x < i; x++){
printf("Ange år: ");
scanf("%d", ??? )
}
}
}
#include <stdlib.h>
...
printf("Ange antal vinnare:");
scanf("%d", &i);
//i = i - 1;//remove
vinnare = malloc(i * sizeof(struct vinnareinfo));//check return value of malloc
for (x = 0; x < i; x++){
printf("Ange ar: ");
scanf("%d", &vinnare[i].ar);
}
to make things easier and more readable consider defining a new data type for your structure:
typedef struct {
char fornamn[20];
char efternamn[20];
int ar;
}vinnareinfo;
You can find more useful info about it here
scanf("%d", &i);
vinnareinfo *v = (vinnareinfo*)malloc((i-1)*sizeof(vinnareinfo)); //allocated an array of i elements of type vinnareinfo
I hope this is what you were looking for.
if (fscanf(file, "%d", &i) != 1) {
perror("fscanf");
exit(1);
}
vinnare = malloc(sizeof(struct vinnareinfo) * i);
if (!vinnare) {
perror("malloc");
exit(1);
}
for (x = 0; x < i; x++) {
int rc = fscanf(file, "%*s%*s%d",
sizeof(vinnare->fornamn)-1, &vinnare->fornamn,
sizeof(vinnare->efternamn)-1, &vinnare->efternamn,
&vinnare->ar);
vinnare++;
if (rc <= 0) {
perror("fscanf");
break;
}
}
NB May be need to replace '*' in fscanf formatting string by '19', and remove 'sizeof(vinnare->...)-1' args. That works for printf, but should be tested for scanf!
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