1. Name

2. Synopsis

nl [OPTION]... [FILE]... 

3. Frequently used options

-b, --body-numbering=STYLE
    use STYLE for numbering body lines
-f, --footer-numbering=STYLE
    use STYLE for numbering footer lines
-h, --header-numbering=STYLE
    use STYLE for numbering header lines 

4. Examples

$ echo -e "one\ntwo\nthree\nfour\nfive\n\nsix" > file 

$ nl file