How to add line numbers to a text file?

[WU SHI-KUEI]

With System V you have several choices for numbering lines in text files,
none of which use sed, awk, perl etc., etc.:

1. If the document will be formatted with n/troff, turn on line numbering
   with the .nm request.

2. If the document has been formatted and is paginated, 'pr -tn file' will
   do just fine if you don't mind having all lines numbered.

3. The line numbering filter 'nl' offers all sorts of options worth
   exploring.

Regardless of your choice, RTFM.