(C Programming) User name and Password Identification

Question

Why do I get format '%s' expects argument of type 'char*'? How should I fix the problem?

Here are my codes:

char UserName[] = "iluvcake";
scanf("%s", &UserName);
printf("Please enter your password: \n");
char PassWord[] = "Chocolate";
scanf("%s", &PassWord);
    //if...else statement to test if the input is the correct username. 
    if (UserName == "iluvcake") 
    {
     if (PassWord == "Chocolate"){
     printf("Welcome!\n");
    }
    }else
    {
     printf("The user name or password you entered is invalid.\n");
    }

Because name of an array is also an address. Do scanf("%s", UserName); instead of scanf("%s", &UserName); — SomeWittyUsername
– SomeWittyUsername, Commented Apr 3, 2013 at 14:51
I know this is not your question, but I simply cannot resist. Dealing with passwords you should always: Turn echo off so the password is not shown during typing, erase the password from memory as soon as you don't need it anymore (overwrite it with 0's) and not hardcode it into your code (use hashes instead). If you put the password into the code it is nealry like putting it into a textfile. — Abu Dun
– Abu Dun, Commented Apr 3, 2013 at 14:55

K Scott Piel · Accepted Answer · 2013-04-03 14:50:12Z

4

&UserName is a pointer to an array of char (i.e., a char**). You should use

scanf( "%s", UserName );

answered Apr 3, 2013 at 14:50

K Scott Piel

4,39016 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Lundin Apr 29 at 10:09

Not char** but char (*)[9].

anishsane · Accepted Answer · 2013-04-03 14:52:05Z

2

scanf for %s takes a char array/pointer, not pointer to it. drop the & from the scanf statements.
You cannot compare strings with ==. Use strcmp.

answered Apr 3, 2013 at 14:52

anishsane

21.1k5 gold badges46 silver badges77 bronze badges

Comments

Johnny Mnemonic · Accepted Answer · 2013-04-03 14:50:11Z

0

Must be

scanf("%s", UserName);
scanf("%s", PassWord);

because UserName and PassWord are pointers to char arrays.

answered Apr 3, 2013 at 14:50

Johnny Mnemonic

3,9605 gold badges24 silver badges33 bronze badges

Comments

Maky · Accepted Answer · 2013-12-30 20:38:16Z

0

#include<stdio.h>
#include<conio.h>
#include<string.h>

main(){
char name[20];
char password[10];
printf("Enter username: ");
scanf("%s",name);
printf("Enter password: ");
scanf("%s",password);
if (strcmp(name, "Admin") == 0 && strcmp(password, "pass") == 0)
printf("Access granted\n");
else printf("Access denied\n");


getch();
}

:)

answered Dec 30, 2013 at 20:38

Maky

251 bronze badge

1 Comment

Hermit Apr 29 at 9:43

Nice working example! it addresses the question. However would you please edit the answer and light on the problem. here is a link stackoverflow.com/help/how-to-answer

Collectives™ on Stack Overflow

(C Programming) User name and Password Identification

4 Answers 4

1 Comment

Comments

Comments

1 Comment

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

1 Comment

Related