How to get CPU info in C on Linux, such as number

Question

This question already has answers here:

How to get the number of CPUs in Linux using C? (7 answers)

Closed 11 months ago.

Is it possible to get such info by some API or function, rather than parsing the /proc/cpuinfo?

Answer 1

You can use this for mostly all kind of linux distro

For C code

 num_cpus = sysconf( _SC_NPROCESSORS_ONLN );

(In QNX systems , you can use num_cpus = sysinfo_numcpu())

For shell scripting, you can use cat /proc/cpuinfo

or use lscpu or nproc commands in linux

Answer 2

No, it is not. Either you must parse cpuinfo file, or some library will do it for you.

Answer 3

Parse the file /proc/cpuinfo. This'll give you lot of details about the CPU. Extract the relevant fields into your C/C++ file.

Answer 4

libcpuid provides a simple API which will directly return all the CPU features, including number of cores. To get the number of cores at runtime, you could do something like this:

#include <stdio.h>
#include <libcpuid.h>

int main(void)
{
    if (!cpuid_present()) {
        printf("Sorry, your CPU doesn't support CPUID!\n");
        return -1;
    }

    struct cpu_raw_data_t raw; 
    struct cpu_id_t data;     

    if (cpuid_get_raw_data(&raw) < 0) { 
        printf("Sorry, cannot get the CPUID raw data.\n");
        printf("Error: %s\n", cpuid_error());
        return -2;
    }

    if (cpu_identify(&raw, &data) < 0) {    
        printf("Sorrry, CPU identification failed.\n");
        printf("Error: %s\n", cpuid_error());
        return -3;
    }

    printf("Processor has %d physical cores\n", data.num_cores);
    return 0;
}

Answer 5

Depending on your flavor of Linux you will get different results from /proc/cpuid.

This works for me on CentOS for getting total number of cores.

cat /proc/cpuinfo | grep -w cores | sed -e 's/\t//g' | awk '{print $3}' | xargs | sed -e 's/\ /+/g' | bc

The same doesn't work in Ubuntu. For Ubuntu you can use the following command.

nproc

Answer 6

Have you ever seen the output of this shell command "cat /proc/cpuinfo"? I think there you can get out all the information that you need. To read the information in a C program I would prefer the file manipulation functions like fopen, fgets and so on.