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C program to design Login Screen by validation username and password



In this C program, we are going to design a login screen that will read and validate username, password with given values.
Submitted by IncludeHelp, on April 28, 2018

Read username and password and check it with the given values (just like, login screen) using C program.

In this program we will design a login screen to check username and password, password will display as password characters (‘*’) and here backspace key will also work.

This program in compatible with GCC Linux and TurboC compliers, read the given instruction in the program comments.

Program for validating username and password in C

#include <stdio.h>
#include <termios.h> // in gcc, use < conio.h > in turboc
#include <string.h>
 
#define USERNAME    "user001"
#define PASSWORD    "[email protected]"
 
/************************************************
THIS CODE IS USED IN GCC LINUX
because getch() is not defined in library file
************************************************/
 
static struct termios old, new;
 
/* Initialize new terminal i/o settings */
void initTermios(int echo)
{
  tcgetattr(0, &old); /* grab old terminal i/o settings */
  new = old; /* make new settings same as old settings */
  new.c_lflag &= ~ICANON; /* disable buffered i/o */
  new.c_lflag &= echo ? ECHO : ~ECHO; /* set echo mode */
  tcsetattr(0, TCSANOW, &new); /* use these new terminal i/o settings now */
}
 
/* Restore old terminal i/o settings */
void resetTermios(void)
{
  tcsetattr(0, TCSANOW, &old);
}
 
/* Read 1 character - echo defines echo mode */
char getch_(int echo)
{
  char ch;
  initTermios(echo);
  ch = getchar();
  resetTermios();
  return ch;
}
 
/* Read 1 character without echo */
char getch(void)
{
  return getch_(0);
}
 
/* Read 1 character with echo */
char getche(void)
{
  return getch_(1);
}
 
/* function :   getPassword(),
   to get password from keyboard    */
 
void getPassword(char *pass)
{
    int c=0;
    char buff[30]={0},ch;
    int len=0;
    while((ch=getch())!='\n')
    {
        if(ch==0x7f)    // use 0x08 in turboc (WINDOWS)
        {
            if(len==0)  continue;
            printf("\b \b"); len--; continue;
        }
        printf("%c",'*');
        pass[len]=ch;
        len++;
    }
    pass[len]='\0';
 
}
 
int main()
{
 
    char user[30],pass[30];
    printf("Enter User Name :");
    gets(user);
    printf("Enter Password  :");
    getPassword(pass);
     
    if(strcmp(user,USERNAME)==0 && strcmp(pass,PASSWORD)==0)
        printf("\nLOGIN SUCCESS.\n");
    else
        printf("\nLOGIN FAILED.\n");
    return 0;
}

Output

    Enter User Name :user001
    Enter Password  :******
    LOGIN SUCCESS. 





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