check centos version code example
Example 1: check centos version
$ cat /etc/redhat-release
output : CentOS Linux release 7.4.1708 (Core)
Example 2: how to know which centos version is installed
<p>On the GUI (Gnome) upper right corner click on settings and then on details </p>
By command line
cat /etc/centos-release
This command works also changing the word centos by os (os-release)