User Input to File - c

Question

I'm creating a program that should create a structure of a list of people entered by the user; the only problem I'm having is getting the user input data to appear in the text file. Anyone know how to do this? Here is the code:
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
struct person{
char name[20];
int age;
struct person *next_ptr;
} PERSON;
int main (void){
struct person PERSON;
FILE *fp;
char ans, ch;
int ppl=0;
fp=fopen("person_struct", "w");
if(fp != NULL){
while(ppl<25){
printf("Would you like to add a person to the list? [y/n] ");
scanf("%c", &ans);
if(ans == 'y') {
printf("\nEnter a name:\n");
scanf("%s", PERSON.name);
fprintf(fp, "%s",PERSON.name);
printf("\nEnter age:\n");
scanf("%i", &PERSON.age);
fprintf(fp, " %i\n", PERSON.age);
}
else {
ppl=25;
}
ppl++;
}
fclose(fp);
}
printf("\n\n\n");
system("pause");
return 0;
}

Answer 1

Youe scanf statement is wrong you forgot ampersand & operator before PERSON.age its int
scanf("%i", PERSON.age);
^ & missing
correct is:
scanf("%i", &PERSON.age);
You have two scanf stamens in your code to inputs from user one for string to scan name.
scanf("%s", PERSON.name);
This is correct and No need of & before string. But age is int and to scan int.float you need to add & before variable that is why added ampersand & before PERSON.age.
ref: scanf
Second:
fputs(PERSON.age, fp); is wrong syntax of fputs is:
int fputs( const char *str, FILE *stream );
^ you are passing int
first argument should be const char* but your are passing int
fputs(PERSON.age, fp);
^ wrong , age is int not char*
When you need formatting input/output prefer printf and scanf functions, My suggestion change your read/write like: (read comments)
printf("Enter a name:\n");
scanf("%s", PERSON.name); // here is No & because `name` is string
scanf("%i", &PERSON.age); // age is `int` so & needed
fprintf(fp,"%s %i\n",PERSON.name, PERSON.age);
EDIT: Because you commented, your code is working after these rectifications, see
$ gcc x.c -Wall
$ ./a.out
Would you like to add a person to the list? [y/n]y
Enter a name:
yourname
14
Would you like to add a person to the list? [y/n]y
Enter a name:
firendName
15
Would you like to add a person to the list? [y/n]n
sh: 1: pause: not found
$ cat person_struct.txt
yourname 14
firendName 15

Answer 2

In addition to Grijesh's answer:
Please explain scanf("%s", &ans);. How many characters can you store in ans? How many characters does the string "y" require to store? Verify your beliefs: printf("sizeof ans: %zu\n" "sizeoof \"y\": %zu\n", sizeof ans, sizeof "y");
Perhaps you meant: if (scanf("%c", &ans) != 1) { /* assume stdin has closed or reached EOF */ }. Note the %c, which will read only one character into ans.
Alternatively, if you change ans to an int, you can use: ans = getchar();
edit: In short, I think your loop should look something like this:
for (size_t ppl = 0; ppl < 25; ppl++){
int ans;
printf("Would you like to add a person to the list? [y/n]");
do {
ans = getchar();
while (ans >= 0 && isspace(ans));
if (ans != 'y') {
break;
}
printf("Enter a name:\n");
if (scanf("%s", PERSON.name) != 1 || scanf("%i", &PERSON.age) != 1) {
break;
}
fprintf(fp, "%s %i\n", PERSON.name, PERSON.age);
}