With python, the command python
starts 2.x, and python3
starts the 3.x python interpreter. I think ruby is the same,
I was running the ruby command with no arguments. Then, the line breaks to the next line, but the prompt is not displayed and the process does not end.
The cause was the wrong command. The interpreter for ruby was ʻirb. Use the
ruby` command to evaluate a string as ruby in a script file or with the -e option.