How do I retrieve the number of processors on C / Linux?

Question

I am writing a small C application that use some threads for processing data. I want to be able to know the number of processors on a certain machine, without using system() & in combination to a small script.

The only way i can think of is to parse /proc/cpuinfo. Any other useful suggestions ?

Answer 1

As others have mentioned in comments, this answer is useful:

numCPU = sysconf( _SC_NPROCESSORS_ONLN );

Leaving as a solution for folks that might skip over comments...

Answer 2

Why not use sys/sysinfo.h?

#include <sys/sysinfo.h>
#include <stdio.h>
void main () {
   printf ("You have %d processors.\n", get_nprocs ());
}

Way more information can be found on the man page

$ man 3 get_nprocs