# nl
# Number lines of files

# Number lines given to nl(1) via STDIN.
printf "Here\nis\nsome\nexample\ntext." | nl

# Number (all) lines given to nl(1) via provided file(s).
nl -b a /path/to/file
# The above can also be achieved with cat(1), which is perhaps more portable:
cat -n /path/to/file