man3/get_nprocs_conf.3

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  26 .TH GET_NPROCS 3   2019-03-06 "GNU" "Linux Programmer's Manual"
  27 .SH NAME
  28 get_nprocs, get_nprocs_conf \- get number of processors
  29 .SH SYNOPSIS
  30 .B #include <sys/sysinfo.h>
  31 .PP
  32 .BI "int get_nprocs(void);"
  33 .br
  34 .BI "int get_nprocs_conf(void);"
  35 .SH DESCRIPTION
  36 The function
  37 .BR get_nprocs_conf ()
  38 returns the number of processors configured by the operating system.
  39 .PP
  40 The function
  41 .BR get_nprocs ()
  42 returns the number of processors currently available in the system.
  43 This may be less than the number returned by
  44 .BR get_nprocs_conf ()
  45 because processors may be offline (e.g., on hotpluggable systems).
  46 .SH RETURN VALUE
  47 As given in DESCRIPTION.
  48 .SH ATTRIBUTES
  49 For an explanation of the terms used in this section, see
  50 .BR attributes (7).
  51 .TS
  52 allbox;
  53 lb lb lb
  54 l l l.
  55 Interface       Attribute       Value
  56 T{
  57 .BR get_nprocs (),
  58 .br
  59 .BR get_nprocs_conf ()
  60 T}      Thread safety   MT-Safe
  61 .TE
  62 .sp 1
  63 .SH CONFORMING TO
  64 These functions are GNU extensions.
  65 .SH NOTES
  66 The current
  67 .\" glibc 2.15
  68 implementation of these functions is rather expensive,
  69 since they open and parse files in the
  70 .I /sys
  71 filesystem each time they are called.
  72 .PP
  73 The following
  74 .BR sysconf (3)
  75 calls make use of the functions documented on this page
  76 to return the same information.
  77 .PP
  78 .in +4n
  79 .EX
  80 np = sysconf(_SC_NPROCESSORS_CONF);     /* processors configured */
  81 np = sysconf(_SC_NPROCESSORS_ONLN);     /* processors available */
  82 .EE
  83 .in
  84 .SH EXAMPLE
  85 The following example shows how
  86 .BR get_nprocs ()
  87 and
  88 .BR get_nprocs_conf ()
  89 can be used.
  90 .PP
  91 .EX
  92 #include <stdlib.h>
  93 #include <stdio.h>
  94 #include <sys/sysinfo.h>
  95
  96 int
  97 main(int argc, char *argv[])
  98 {
  99     printf("This system has %d processors configured and "
 100             "%d processors available.\en",
 101             get_nprocs_conf(), get_nprocs());
 102     exit(EXIT_SUCCESS);
 103 }
 104 .EE
 105 .SH SEE ALSO
 106 .BR nproc (1)