How to set an alias inside a bash shell script so that is it visible from the outside?

problem ：

OSX: This works from the command line:OSX： This can work from the command line ：

alias ruby="/opt/local/bin/ruby1.9"

but in side a shell script, it has no effect. But in shell Script , It has no effect .I want to write a script that will switch between ruby 1.8 and ruby 1.9, so this needs to be a script - not in my profile. I want to write a ruby 1.8 and ruby 1.9 Switch between scripts , So this needs to be a script - Not in my profile .

It appears "source script.sh" works, but "./script.sh". look “source script.sh” It works , however “./script.sh”.Why is this? Why is that ？How can I replicate this in my script? How can I copy this in the script ？

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Solution ：

Reference resources ： https://stackoom.com/en/question/9Dev