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

NAME         top

       get_nprocs, get_nprocs_conf - get number of processors

SYNOPSIS         top

       #include <sys/sysinfo.h>

       int get_nprocs(void);
       int get_nprocs_conf(void);

DESCRIPTION         top

       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).

RETURN VALUE         top

       As given in DESCRIPTION.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).

       ┌──────────────────┬───────────────┬─────────┐
       │Interface         │ Attribute     │ Value   │
       ├──────────────────┼───────────────┼─────────┤
       │get_nprocs(),     │ Thread safety │ MT-Safe │
       │get_nprocs_conf() │               │         │
       └──────────────────┴───────────────┴─────────┘

CONFORMING TO         top

       These functions are GNU extensions.

NOTES         top

       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 */

EXAMPLE         top

       The following example shows how get_nprocs() and get_nprocs_conf()
       can be used.

       #include <stdlib.h>
       #include <stdio.h>
       #include <sys/sysinfo.h>

       int
       main(int argc, char *argv[])
       {
           printf("This system has %d processors configured and "
                   "%d processors available.\n",
                   get_nprocs_conf(), get_nprocs());
           exit(EXIT_SUCCESS);
       }

SEE ALSO         top

       nproc(1)

COLOPHON         top

       This page is part of release 4.15 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

GNU                              2017-09-15                    GET_NPROCS(3)

Pages that refer to this page: sched_setaffinity(2),  sysconf(3)

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