How do I get system information by C/C++

cs87668 · 06-12-2003, 10:38 PM

Dear all,

I want to get some informtion of system by C/C++ Language, such as:

1. CPU (These are percentages of total CPU time)
us: user time
sy: system time
id: idle time

2. Procs
r: The number of processes waiting for run time.
b: The number of processes in uninterruptable sleep.
w: The number of processes swapped out but otherwise runnable.

I have traced the source code of "vmstat", and it is too complex to understand.

Can anyone help me and give me some hits,

thank you~

yixudong · 06-12-2003, 11:06 PM

first of all ,C language does not provide any funtion like this.

Maybe you can find or write a library to do the tasks upon.

I think you should find them in the kernel struct although it is not the best way.And the entries you want is served more to the kernel ,not to the user,so it is hard to find a function.

aizkorri · 06-13-2003, 02:44 AM

I think its easyer to call system functions like 'ps -x' from C.

turnip · 06-13-2003, 04:42 AM

something like

Code:

#include <stdio.h>
#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>


int main(){

char buffer[5000];

        system("top > output");

        ifstream output ("output");
        output.read (buffer,5000);
        cout << buffer << endl;

        ofstream outputfile ("output");
        outputfile << "";
        outputfile.close();

        system("rm output");
}

should give you what you are looking for.

you can also add another system("vmstat >> output");

for a little more information.

hope this helped.

AMDPwred · 06-14-2003, 12:35 AM

I believe some of this info is scattered around in the /proc/ directory as well.

benguin · 06-14-2003, 02:04 PM

/proc directory indeed.
use a c++ istream to open and read /proc/loadavg. That'd give you the load values.
you can use turnips way to get the process info.

:-)

cs87668 · 06-14-2003, 10:28 PM

thanks for everyboady's reply,

I trace the source code of procps package (including vmstat.c, sysinfo.c...) finally
But I still don't understand that the algorithm of code and the equation which calculate the sysytem information value.

Now, I copy some part of codes from the package, and I can get the information which I need now.

Hko · 06-15-2003, 05:51 AM

You may want to have a look at RedHat reference on the proc filesystem.