how to number lines in a file with sed and paste

file testfile contents:

spam
eggs
foo
bar

number the lines:

sed = testfile | paste -s -d '\t\n' - -

output (written to the terminal):

1       spam
2       eggs
3       foo
4       bar

number the lines and save to a new file:

sed = testfile | paste -s -d '\t\n' - - >testfile.numbered

that’s all folks!
…dave
Wed Oct 25 22:31:46 UTC 2017