nl(1posix) - line numbering filter
-b  type
       Specify which logical page body lines shall be numbered. Recognized types and their meaning are:
-d  delim
       Specify  the  delimiter characters that indicate the start of a logical page section. These can be
       changed from the default characters "\:" to two user-specified characters. If only  one  character
       is entered, the second character shall remain the default character ':' .
-f  type
       Specify  the  same as b type except for footer. The default for logical page footer shall be n (no
       lines numbered).
-h  type
       Specify the same as b type except for header. The default type for logical page header shall be  n
       (no lines numbered).
-i  incr
       Specify the increment value used to number logical page lines. The default shall be 1.
-l  num
       Specify  the  number of blank lines to be considered as one. For example, -l 2 results in only the
       second adjacent blank line being numbered (if the appropriate -h a, -b a, or -f a option is  set).
       The default shall be 1.
-n  format
       Specify  the  line  numbering  format.  Recognized  values  are: ln, left justified, leading zeros
       suppressed; rn, right justified, leading zeros suppressed;  rz,  right  justified,  leading  zeros
       kept. The default format shall be rn (right justified).
-p     Specify that numbering should not be restarted at logical page delimiters.
-s  sep
       Specify  the  characters  used  in separating the line number and the corresponding text line. The
       default sep shall be a <tab>.
-v  startnum
       Specify the initial value used to number logical page lines. The default shall be 1.
-w  width
       Specify the number of characters to be used for the line number. The default width shall be 6.