Adding alias to end of alias list in .bashrc file using sed

Question

I'm writing a shell script that I want to add an alias to the end of the alias list in the .bashrc file. I'm thinking something with sed would work, just not sure how to find the last line that begins with alias, then add on the next line another alias.

Answer 1

Why do you need to add it to an "alias list"? If you don't have additional requirements that you did not specify in the question, just append your alias to .bashrc:

echo "alias youralias='yourcmd'" >> /home/user/.bashrc

Answer 2

When I hear "do something after the last whatever", I think of reversing the file and do something when I see the first whatever:

tac .bashrc | 
awk -v newalias="alias new=foo" '$1 == "alias" {print newalias} 1' | 
tac > .bashrc.new
mv .bashrc .bashrc.$(date +%Y%m%d%H%M%S) && mv .bashrc.new .bashrc