nl

nl - number lines of files.

Number lines of a file:

nl file.txt

Number empty lines of a file:

nl -b a file.txt

Change line number increment value:

nl -i 3 file.txt

Change the starting line number:

nl -v 5 file.txt

Treat multiple lines as one:

nl -b a -l 2 file.txt

Number lines of a file using left justified format:

nl -n ln file.txt

Number lines of a file using right justified format:

nl -n rn file.txt

Number lines of a file using right justified format (with leading zeros):

nl -n rz file.txt

Change line number separator:

nl -s ';' file.txt