CPU Percentage use value

Question

Note(Not my code): SOURCE Bottom of page made by Sayyed Mohsen Zahraee. I made some minor changes in my post but his original code works right off the bat.

While trying to see how this code works, I'm also trying to find a way to have the final output, when meeting a certain parameter through an if statement, trigger an action.

#include <iostream>
#include <windows.h>
#include <stdio.h>

void GetSystemTimesAddress();
CHAR cpuusage();


int main(void)
{
    int n;
    GetSystemTimesAddress();
    for(n=0;n<20;n++)
    {
        printf("CPU Usage: %3d%%\r",cpuusage());
        Sleep(2000);
        if ((printf("%3d%%\r",cpuusage())) = '10')//Doesn't work but goal action
        {
            std::cout << "just fine";
        }
        if ((printf("%3d%%\r",cpuusage())) = '30')
        {
            std::cout << "keep an eye on";
        }
        if ((printf("%3d%%\r",cpuusage())) = '50')
        {
            std::cout << "getting warm";
        }
        if ((printf("%3d%%\r",cpuusage())) = '70')
        {
            std::cout << "pretty dangerous";
        }
    }
    printf("\n");
    return 0;
}

//Bellow CPU usage meathods
    CHAR cpuusage(void);

    typedef BOOL ( __stdcall * pfnGetSystemTimes)( LPFILETIME lpIdleTime, LPFILETIME lpKernelTime, LPFILETIME lpUserTime );
    static pfnGetSystemTimes s_pfnGetSystemTimes = NULL;
    static HMODULE s_hKernel = NULL;
    void GetSystemTimesAddress()
    {
        if( s_hKernel == NULL )
        {   
            s_hKernel = LoadLibrary( L"Kernel32.dll" );
            if( s_hKernel != NULL )
            {
                s_pfnGetSystemTimes = (pfnGetSystemTimes)GetProcAddress( s_hKernel, "GetSystemTimes" );
                if( s_pfnGetSystemTimes == NULL )
                {
                    FreeLibrary( s_hKernel ); s_hKernel = NULL;
                }
            }
        }
    }
    // cpuusage(void)
    // Return a CHAR value in the range 0 - 100 representing actual CPU usage in percent.
    CHAR cpuusage()
    {
        FILETIME               ft_sys_idle;
        FILETIME               ft_sys_kernel;
        FILETIME               ft_sys_user;

        ULARGE_INTEGER         ul_sys_idle;
        ULARGE_INTEGER         ul_sys_kernel;
        ULARGE_INTEGER         ul_sys_user;

        static ULARGE_INTEGER    ul_sys_idle_old;
        static ULARGE_INTEGER  ul_sys_kernel_old;
        static ULARGE_INTEGER  ul_sys_user_old;

        CHAR  usage = 0;

        // we cannot directly use GetSystemTimes on C language
        /* add this line :: pfnGetSystemTimes */
        s_pfnGetSystemTimes(&ft_sys_idle,    /* System idle time */
            &ft_sys_kernel,  /* system kernel time */
            &ft_sys_user);   /* System user time */

        CopyMemory(&ul_sys_idle  , &ft_sys_idle  , sizeof(FILETIME)); // Could been optimized away...
        CopyMemory(&ul_sys_kernel, &ft_sys_kernel, sizeof(FILETIME)); // Could been optimized away...
        CopyMemory(&ul_sys_user  , &ft_sys_user  , sizeof(FILETIME)); // Could been optimized away...

        usage  =
            (
            (
            (
            (
            (ul_sys_kernel.QuadPart - ul_sys_kernel_old.QuadPart)+
            (ul_sys_user.QuadPart   - ul_sys_user_old.QuadPart)
            )
            -
            (ul_sys_idle.QuadPart-ul_sys_idle_old.QuadPart)
            )
            *
            (100)
            )
            /
            (
            (ul_sys_kernel.QuadPart - ul_sys_kernel_old.QuadPart)+
            (ul_sys_user.QuadPart   - ul_sys_user_old.QuadPart)
            )
            );

        ul_sys_idle_old.QuadPart   = ul_sys_idle.QuadPart;
        ul_sys_user_old.QuadPart   = ul_sys_user.QuadPart;
        ul_sys_kernel_old.QuadPart = ul_sys_kernel.QuadPart;

        return usage;
    } 

If someone finds a way to make the if staments work, could you give a brief explanation as to how it does. I understand something like this is difficult to explain in a simple paragraph or two, but even something simple would be a great learning opportunity. Thank You!

Answer 1

You are assigning when you mean to be comparing. This is a common problem here on the Stack. You're also attempting to compare whatever is returned from printf. Furthermore, you're attmepting to make a character out of two characters. '10' is invalid. It could be a C-String, "10", but more than likely you want an int. Change the if's from:

if ((printf("%3d%%\r",cpuusage())) = '10')

To

if(cpuusage() == 10)