Thread: question about comparing text in a file...

How would I get my program to compare user imput to text stored in a file? Like checking to see if the user entered the correct password.

Thanks for the help.

Open the file, read the password, close the file, read input from user and strcmp() it.

Read the password from the file, store it in a string and then compare it to the user input.

No matter what I enter in for the password it prints out that i have entered it in wrong, What did I do wrong, here is my code.

Code:

#include <fstream.h>
#include <iostream.h>

int main()
{
  int end;
  char password[21];
  char realpass[21];
  cout<<"Password:\n";
  cin.get(password , 20);
  ifstream a_file ( "password.txt" );

  a_file>> realpass;
  if (password != realpass)

  { cout<<"You have wrongly entered the password \n"; }

  else
  { cout<< "you have correctly entered the password\n"; }
  cin >> end;
 return 0; }

Use strcmp(), and you don't need the curly things for only one statement.

Example:

Code:

if( strcmp(bleh, blah))
     cout << "oh my word";
else
     cout << "more word action";

EDIT: Added code tags.

i used strcmp but it still says i have entered in the wrong code no matter what i put in

Code:

#include <fstream.h>
#include <iostream.h>

int main()
{
  int end;
  char password[21];
  char realpass[21];
  cout<<"Password:\n";
  cin.get(password , 20);
  ifstream a_file ( "password.txt" );

  a_file>> realpass;
  if (strcmp(password , realpass))

   cout<<"You have wrongly entered the password \n";

  else
   cout<< "you have correctly entered the password\n";
  cin >> end;
 return 0; }

ok i am confused, what is the difference in a string and a character array, sorry if it is a stupid question.

Simply put a string is a character array that changes it size when needed so you aren't restricted to a set like 21 in your program.
The string class is also the C++ way of handling text but it is of course still legal and ok to use character arrays if you want.

'string' is the C++ string type. Essentially a way to make your life much, much easier in C++.
Don't use char[] or strcmp unless you want to make life difficult (or if you're programming in C rather than C++)
eg,

Code:

#include <iostream>
#include <string>
using namespace std;

int main()
{
   const string password = "mypass";
   string input;
   cin >> input;
   if (password == input)
      cout << "Password match";
}

Much easier to read and understand!

Originally Posted by Bench82

'string' is the C++ string type. Essentially a way to make your life much, much easier in C++.
Don't use char[] or strcmp unless you want to make life difficult (or if you're programming in C rather than C++)
eg,

Code:

#include <iostream>
#include <string>
using namespace std;

int main()
{
   const string password = "mypass";
   string input;
   cin >> input;
   if (password == input)
      cout << "Password match";
}

Much easier to read and understand!

how woul i get this to check and see if the password the user entered matched teh first line of the file named list.txt?

Was i doing that right in my previous post?

Originally Posted by WaltP

Argggghhhh!!! (this to the other helpful posts)
What you did wrong is not find out what was actually read from the file/user.

This is always the easiest way to find out what is wrong. It works most of the time:
After you read password, display it:

Code:

cout << "[" << password << "]" << endl;

Surrounding the input with [ and ] lets you see of the newline is in the value or not.

thank you, turns out i needed to put C://password.txt instead of password.txt but it works now

thank you for your help