get_nprocs(3) — Linux manual page

get_nprocs(3)            Library Functions Manual           get_nprocs(3)

NAME         top

       get_nprocs, get_nprocs_conf - get number of processors

LIBRARY         top

       Standard C library (libc, -lc)

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(), get_nprocs_conf()      │ Thread safety │ MT-Safe │
       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS         top

       GNU.

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 */

EXAMPLES         top

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

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

       int
       main(void)
       {
           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

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Linux man-pages 6.15            2025-05-17                  get_nprocs(3)

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

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