How to get the number of CPUs in Linux using C?

Question

Is there an API to get the number of CPUs available in Linux? I mean, without using /proc/cpuinfo or any other sys-node file...

I\'ve found this implementation using

Answer 1

Using /proc/cpuinfo is the cleanest and most portable solution. In case the open fails, you could simply assume 1 cpu or 2 cpus. Code that depends on knowing the number of cpus for a purpose other than micro-optimizing (e.g. choosing the ideal number of threads to run) is almost surely doing something dumb.

The _SC_NPROCESSORS_ONLN solution depends on a non-standard (glibc-specific) sysconf extension, which is a much bigger dependency than /proc (all Linux systems have /proc, but some have non-glibc libcs or older versions of glibc that lack _SC_NPROCESSORS_ONLN).