How do I append lines from one file to the end of each line of another file?

Question

Suppose I have two files:

cat
dog
baboon

feline
canine
primate

I want to append the lines from one file at the end of another file after

Answer 1

paste --delimiter=' ' file1 file2

Note: the result will be written to stdout. If you want to store the result in a file, use a redirection operator:

paste --delimiter=' ' file1 file2 > outputfile

Run man paste for more information about the command.