How to display a certain set of data File Handling C - c

Question

so I am thinking if there's a way that I could display one set of data inputted. So my sample program operates like this:
The user inputs a name, gender, and an age. The user can input multiple data. But I want to add a function where the user will type in a name, and then displays the name, and its corresponding gender, and age. But the thing is, I have no idea to do that. I heard of a function fseek() but I think it just edits the value; for example, age or gender.
Here is my sample code:
#include <stdio.h>
#include <stdlib.h>
struct clientName {
char name[30];
char gender[10];
};
struct clientAge {
int age;
};
void main() {
FILE *fp;
fp = fopen("data.txt", "ab");
struct clientName NAME;
struct clientAge AGE;
if(fp == NULL){
printf("Error");
getch();
} else {
system("cls");
printf("Enter Name: ");
gets(NAME.name);
printf("Enter Gender: ");
gets(NAME.gender);
printf("Enter Age: ");
scanf("%d", &AGE.age);
fwrite((char *)&NAME, sizeof(struct clientName), 1, fp);
fwrite((char *)&AGE, sizeof(struct clientAge), 1, fp);
printf("\n\nData Added");
fclose(fp);
}
system("cls");
fp = fopen("data.txt", "rb");
while((fread((char *)&NAME, sizeof(struct clientName), 1, fp)) == 1 & (fread((char *)&AGE, sizeof(struct clientAge), 1, fp)) == 1) {
printf("%s", NAME.name);
printf(" %s", NAME.gender);
printf(" %d y/o", AGE.age);
printf("\n");
}
fclose(fp);
}

Answer 1

There are a couple of problems i see with your code. I'll first try to correct it and then provide a full example of how I would do what you want done.
struct clientName {
char name[30];
char gender[10];
};
struct clientAge {
int age;
};
Why are you using 2 structs for 1 dataset?
Use
struct data
{
char name[30];
char gender[10];
int age;
};
instead.
fwrite((char *)&NAME, sizeof(struct clientName), 1, fp);
can be written as: fwrite(&client, sizeof(client), 1, fp);
while((fread((char *)&NAME, sizeof(struct clientName), 1, fp)) == 1
& (fread((char *)&AGE, sizeof(struct clientAge), 1, fp)) == 1)
can be written as: while (fread(&client, sizeof(client), 1, fp))
after which you only have to compare the client.name variable with your user input name like so:
if (strcmp(client.name, input) == 0)
Please note that I only opted to use one struct on purpose, as I do not see why it would be beneficial to use 2 structs in your use case.
If you, however do need to use 2 structs you can simply add an 'ID' integer variable to both of them and find all data points to any given name that way.
Full code example:
struct data
{
char name[30];
char gender[10];
int age;
};
int main(void)
{
struct data client;
FILE* fp;
char ch = 0;
do
{
printf("Enter Name: ");
scanf("%s", client.name);
printf("Enter Gender: ");
scanf("%s", client.gender);
printf("Enter Age: ");
scanf("%d", &client.age);
fp = fopen("Data.dat", "ab");
fwrite(&client, sizeof(client), 1, fp);
fclose(fp);
printf("continue? \n");
scanf(" %c", &ch);
} while (ch != 'n'); // continuously appends file till letter n is read;
char input[30]; // user input
printf("name?\n"); // please note that you could pretty much use every other data point here.
scanf("%s", input);
struct data Read; // used different for showcasing purposes only
fp = fopen("Data.dat", "rb");
while (fread(&client, sizeof(client), 1, fp))
{
if (strcmp(client.name, input) == 0) // compare variable with user input
{
printf("%s", client.name);
printf(" %s", client.gender);
printf(" %d y/o", client.age);
printf("\n");
}
}
return 0;
}