CODEWITHSUNDEEP
clinux
Abhijatya Singh
Abhijatya Singh

Reputation: 642

Input from scanf function giving unexpected result

I was trying to get user name and password for authentication on a linux system and gcc-4.7 compiler as follows:

#include "stdio.h"
#include "stdlib.h"
#include <termios.h>
#include <unistd.h>

void getuserdata(char *passwd)
{
    struct termios term, term_orig;
    tcgetattr(STDIN_FILENO, &term);
    term_orig = term;
    term.c_lflag &= ~ECHO;
    tcsetattr(STDIN_FILENO, TCSANOW, &term);

    scanf("%s", passwd);
    /* Remember to set back, or your commands won't echo! */
    tcsetattr(STDIN_FILENO, TCSANOW, &term_orig);

}

int main()
{
    char *password, *username;
    printf("Enter username: ");
        scanf("%s", username);
        fflush(stdin); 
    printf("\n");

    printf("\nEnter password: ");
    getuserdata(password);

    printf("Entered username is:%s\n", username);
    printf("Entered password is:%s\n", password);
    return 0;
}

and expected behaviour was as follows:

Enter username: test 
Enter password:
Entered username is: test 
Entered password is: xxxx

But it is not working and giving null as username or password.

Guys where am I going wrong?

Any help would be greatly appreciated.

Thanks.

Upvotes: 0

Views: 87

Answers (1)

Haris
Haris

Reputation: 12270

You did not allocate memory for username and password.

char *password, *username;
username = malloc(50);
printf("Enter username: ");
    scanf("%49s", username);

printf("\n");

printf("\nEnter password: ");
password = malloc(50);
getuserdata(password);

Upvotes: 3

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