How to give access to text file using if statement? - c

Question

I am trying to give an if statement to check if a particular name is present in text file, then give access to it otherwise give error message.
#include <stdio.h>
#include <stdlib.h>
int main(){
printf("For person details, please enter the person name: \n");
FILE * fr = fopen("/home/bilal/Documents/file.txt","r");
int catch, i=0, index=0;
char ch[100];
printf("Enter your Name: ");
if (scanf("%s", )){ // Don't know what to put here?
perror("Error while reading!");
return 0;
}
catch = fgetc(fr);
while(catch != EOF){
ch[index] = catch;
if (ch[index] == ' '){
ch[index] = '\0';
printf("Here is your result: %s\n",ch);
index = 0;
i++;
}
else
index++;
catch = fgetc(fr);
}
fclose(fr);
return 0;
}

Answer 1

Simply the program firstly opens a file and asks for a user input and verifies if the provided content is case-sensitively matched with the file. If so, then it'll let the program access the entire file and display on the screen, to do that, we must use another FILE b/c the old *fp is already manipulated and in case it's reused, it may display wrong data.
#include <stdio.h>
#include <string.h>
int main(void) {
FILE *fp = fopen("file.txt", "r"); // for verification
FILE *fp1 = fopen("file.txt", "r"); // for future use
char ch[50], str[50];
short int FLAG = 0;
printf("Enter the string: ");
scanf("%s", &str); // asks for input
while (fscanf(fp, "%s", ch) != EOF) {
if (!strcmp(ch, str)) { // checks if a string matches provided by the user
printf("Found! Here's your details...\n\n");
FLAG = 1;
}
}
if (!FLAG == 1) { // no? exits.
printf("Not found, access denied!\n");
return -1;
}
fclose(fp);
int c = fgetc(fp1); // yes? let's go...
while (c != EOF) {
printf("%c", c); // displays containing data
c = fgetc(fp1);
}
fclose(fp1);
return 0;
}

Answer 2

You'll want to add a variable for your scanf output:
char name[100];
if (scanf("%s", name) != -1)
// ...
Then to compare both you'll use strcmp.
#include <string.h>
//...
if (strcmp(ch, name) == 0)
// both are equal
Note that you can access documentation for scanf and strcmp by typing man scanf or man strcmp in your terminal.

Answer 3

int main()
{
printf("For person details, please enter the person name and id card
number: \n");
printf("Enter your Name: ");
char personName[100];
scanf("%s", personName);
printf("Enter your card number: ");
int cardNumber;
if (scanf("%d", &cardNumber)){
printf("no error detected");
}
else{
printf("error while reading");
}
return 0;
}

Answer 4

The fixed code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
printf("For person details, please enter the person name: \n");
FILE* fr = fopen("/home/bilal/Documents/file.txt", "r");
int catch, i = 0, index = 0;
char ch[100] = { 0 };
if (fr == NULL)
{
perror("Invalid file opening!");
return 1;
}
printf("Enter your Name: ");
fgets(ch, 100, fr);
size_t len = strcspn(ch, "\n");
ch[(len < 100) ? (len) : (99)] = 0; // For file safety checking
if (strlen(ch)) { // Don't know what to put here?
perror("Error while reading!");
return 1;
}
catch = fgetc(fr);
while (catch != EOF) {
ch[index] = catch;
if (ch[index] == ' ') {
ch[index] = '\0';
printf("Here is your result: %s\n", ch);
index = 0;
memset(ch, 0, 100);
i++;
}
else
{
index++;
}
catch = fgetc(fr);
}
fclose(fr);
return 0;
}