Check out example codes for "ruby install on fedora". It will help you in understanding the concepts better.

Code Example 1

rvm list

   ruby-2.4.4 [ x86_64 ]
 * ruby-2.5.1 [ x86_64 ]
=> ruby-2.7.0 [ x86_64 ]

# => - current
# =* - current && default
#  * - default

Code Example 2

ruby --version

ruby 2.7.0p0 (2019-12-25 revision 647ee6f091) [x86_64-linux]

Code Example 3

source /etc/profile.d/rvm.sh
rvm reload

Code Example 4

sudo -i
dnf install gcc-c++ patch readline readline-devel zlib zlib-devel \
    libyaml-devel libffi-devel openssl-devel make \
    bzip2 autoconf automake libtool bison sqlite-devel

Code Example 5

curl -sSL https://rvm.io/mpapis.asc | gpg2 --import -
curl -sSL https://rvm.io/pkuczynski.asc | gpg2 --import -
curl -L get.rvm.io | bash -s stable

Code Example 6

rvm requirements run

Checking requirements for fedora.
Requirements installation successful.

Code Example 7

rvm use 2.7 --default

Using /usr/local/rvm/gems/ruby-2.7.0

Code Example 8

rvm install 2.7

Code Example 9

rvm list known

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