nl: Number Lines
Published on 21 Sep 2003Tags #Linux
It is often useful to use line numbered code to document the stuff you implemented. So instead of manually adding them or writing YALNT (yet another line numbering tools) you better use nl.
- Creating a file for testing
$ cat >test <<EOF
> heading
> ========
>
> introductionary text
>
>
> chapter
> --------
>
> some more text
> a new paragraph
> EOF
$ _
- Simplified syntax
nl [-b<STYLE>] [-n<FORMAT>] [-s<SEPARATOR>] [-w<WIDTH>]
| Option | Content | Description |
|---|---|---|
| STYLE | a | Number all lines |
| t | Number non-empty lines (DEFAULT) | |
| a | Number no lines | |
| FORMAT | ln | Left justifies, no leading zeros |
| rn | Right justifies, no leading zeros (DEFAULT) | |
| rz | Right justified, leading zeros | |
| SEPARATOR | A string which is inserted between the line number and the line content (DEFAULT: TAB) | |
| WIDTH | The number of characters used for the line number (DEFAULT: 6) |
- Basic usage
$ nl test
1 heading
2 --------
3 introductionary text
4 chapter
5 --------
6 some more text
7 a new paragraph
$ _
- Numbering all lines
In case you do not want empty lines to be left out.
$ nl -ba test
1 heading
2 --------
3
4 introductionary text
5
6
7 chapter
8 --------
9
10 some more text
11 a new paragraph
$ _
- Adjusting the width and padding
Use smaller width for line numbers and zero pad them.
$ nl -ba -nrz -w3 test
001 heading
002 --------
003
004 introductionary text
005
006
007 chapter
008 --------
009
010 some more text
011 a new paragraph
$ _
- Adjusting the separator
Don’t use TAB for separating the line numbers and the content to make the output more dense.
$ nl -ba -nrz -w3 -s" " test
001 heading
002 --------
003
004 introductionary text
005
006
007 chapter
008 --------
009
010 some more text
011 a new paragraph
$ _
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