GET_NPROCS(3) Linux Programmer's Manual GET_NPROCS(3)

get_nprocs, get_nprocs_conf - get number of processors

#include <sys/sysinfo.h>
int get_nprocs(void);
int get_nprocs_conf(void);

The function get_nprocs_conf() returns the number of processors configured by the operating system.

The function get_nprocs() returns the number of processors currently available in the system. This may be less than the number returned by get_nprocs_conf() because processors may be offline (e.g., on hotpluggable systems).

As given in DESCRIPTION.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
get_nprocs (), get_nprocs_conf () Thread safety MT-Safe

These functions are GNU extensions.

The current implementation of these functions is rather expensive, since they open and parse files in the /sys filesystem each time they are called.

The following sysconf(3) calls make use of the functions documented on this page to return the same information.

np = sysconf(_SC_NPROCESSORS_CONF);     /* processors configured */
np = sysconf(_SC_NPROCESSORS_ONLN);     /* processors available */

The following example shows how get_nprocs() and get_nprocs_conf() can be used.
#include <stdlib.h>
#include <stdio.h>
#include <sys/sysinfo.h>
main(int argc, char *argv[])
    printf("This system has %d processors configured and "
            "%d processors available.\n",
            get_nprocs_conf(), get_nprocs());


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