nl – Number lines of files
Write each FILE to stdout, with line numbers added.
With No FILE or -, read stdin
nl myfile — Writes all non-empty lines with number.
nl -ba myfile — Number all lines.
nl -ba -l2 myfile — Count 2 empty line as 1 and display
nl -nln myfile — Numbers are left justified.
nl -nrz myfile — Numbers are right justified and leading zeros
nl -w2 myfile — Uses 2 column for the line number.
nl -s”> ” myfile — Insert “> ” in between number and line.
ls | nl — ls Output with line numbers
Read : man nl