How to save both matching and non-matching from grep

Question

I use grep very often and am familiar with it\'s ability to return matching lines (by default) and non-matching lines (using the -v parameter). However, I want to be able to

Answer 1

Step 1 : Read the file

Step 2 : Replace spaces with a new line and save the result in a temporary file

Step 3 : Get only lines contains '_' from the temporary file and save it into multiwords.txt

Step 4 : Exclude the lines that contains '-' from the temporary file then save the result into singlewords.txt

Step 5 : Delete the temporary file

  cat file | tr ' ' '\n' > tmp.txt | grep '_' tmp.txt > multiwords.txt | grep -v '_' tmp.txt > singlewords.txt | find . -type f -name 'tmp.txt' -delete