This worked with me in Redhat and Ubuntu-based distros:

“less /proc/cpuinfo”

you can get the number of processors easily if you don’t want to read a lot of text:

“less /proc/cpuinfo | grep processor”
processor : 0
processor : 1
processor : 2
processor : 3

The above sample is on my own laptop with a quad-core Intel Core i5 Processor