Anybody tell what wrong in this?

Question

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When i run this function, the printf will print two times

The output will come like

Reboot System
This will end the demo. Continue (Y/N)?Reboot System
This will end the demo. Continue (Y/N)?

tell me how to solve this...

<pre lang="C++"><pre>
void Reboot_System()
{
    while(1)
    {
        char option;
        printf("Reboot System\n");
        printf("\n This will end the demo. Continue (Y/N)?");
        scanf("%c", &option);
        if (option ==  'y' && option == 'Y')
        {
            system("reboot");
            printf("\n Reboot\n");
            while(1);

        }


    }



}

What I have tried:

I tried to print that only once but its not working...

C++

This is my complete code...

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>




void Reboot_System()
{
    while(1)
    {
        char option;
        printf("Reboot System\n");
        printf("\n This will end the demo. Continue (Y/N)?");
        scanf("%c", &option);
        if (option ==  'y' || option == 'Y')
        {
            system("reboot");
            printf("\n Reboot\n");
            while(1);
        }
    }
}

void Shutdown_System()
{
    char option;
    printf("Shutdown System\n");
    printf(".................");
    printf("\n This will end the demo. Continue (Y/N)?");
    scanf("%c", &option);
    if (option ==  'y' || option == 'Y')
    {
        system("shutdown");
        printf("shutdown\n");
    }
}

int main()
{
    char op;
    int n = 0;
    while(1)
    {
        printf("Power Management\n");
        printf("................\n");
        printf("Options:\n");
        printf("1.Reboot\n");
        printf("2.Shutdown\n");
       // printf("\n0.Quit\n");
        scanf(" \n%c", &op);
        switch(op)
        {
          case '1': Reboot_System();
                    break;
          case '2': Shutdown_System();
                    break;
         // case '0': exit(1);
           //         break;
          default : main();
                    break;

        }

    }
    return 0;

}

Posted 21-Jun-21 0:27am

Member 15253975

Updated 21-Jun-21 0:43am

Richard MacCutchan

v2

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Richard MacCutchan · Answer 1 · 2021-06-21T00:30:00

Solution 1

C++

if (option ==  'y' && option == 'Y')

It cannot be equal to both values. It should be:

C++

if (option ==  'y' || option == 'Y') // 'y' OR 'Y'

[edit]
As is often the case this is caused by scanf. Add the following function:

C++

char getOption()
{
    char option[8];
    fgets(option, sizeof option, stdin);
    // NB should check for leading spaces ...

    return option[0];
}

And then replace your scanf calls with:

C++

option = getOption();

[/edit]

Posted 21-Jun-21 0:30am

Richard MacCutchan

Updated 21-Jun-21 1:00am

v2

Comments

Member 15253975 21-Jun-21 6:32am

ok, i tried that but same output came...

[no name] 21-Jun-21 7:00am

See my updated solution.

Member 15253975 21-Jun-21 6:34am

This is my complete code...

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

void Reboot_System()
{
while(1)
{
char option;
printf("Reboot System\n");
printf("\n This will end the demo. Continue (Y/N)?");
scanf("%c", &option);
if (option == 'y' || option == 'Y')
{
system("reboot");
printf("\n Reboot\n");
while(1);
}
}
}

void Shutdown_System()
{
char option;
printf("Shutdown System\n");
printf(".................");
printf("\n This will end the demo. Continue (Y/N)?");
scanf("%c", &option);
if (option == 'y' || option == 'Y')
{
system("shutdown");
printf("shutdown\n");
}
}

int main()
{
char op;
int n = 0;
while(1)
{
printf("Power Management\n");
printf("................\n");
printf("Options:\n");
printf("1.Reboot\n");
printf("2.Shutdown\n");
// printf("\n0.Quit\n");
scanf(" \n%c", &op);
switch(op)
{
case '1': Reboot_System();
break;
case '2': Shutdown_System();
break;
// case '0': exit(1);
// break;
default : main();
break;

}

}
return 0;

}

CPallini 21-Jun-21 7:01am

5.

[no name] 21-Jun-21 7:03am

Thanks. Why do people use scanf? It's the most useless function ever created (in my humble opinion).