Permanently enable a SCL
scl enable actually opens a new shell inside your current one, which is quite unclean, especially if done from a login script.
You should place, instead, in your
source scl_source enable rh-nginx18
The latter is more "elegant" as it is independent from the actual installation path.
This has the effect of loading the environment in your current shell.
Redhat proposes placing a file in
/etc/profile.d, i.e. for python:
$ cat /etc/profile.d/enablepython33.sh #!/bin/bash source scl_source enable python33
As this works for the devtools under centos for me you could try this.