# Lists. Need a bit of help

**URL:** https://discourse.nodered.org/t/lists-need-a-bit-of-help/14157
**Category:** General
**Created:** [8 August 2019 21:30 UTC](https://discourse.nodered.org/t/lists-need-a-bit-of-help/14157 "2019-08-08T21:30:24Z")
**Posts on this page:** 1
**Showing post:** 15

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### Author: ![bakman2](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bakman2/32/6207_2.png) [@bakman2](https://discourse.nodered.org/u/bakman2)
#### Post date: [10 August 2019 15:44 UTC](https://discourse.nodered.org/t/lists-need-a-bit-of-help/14157/15 "2019-08-10T15:44:23Z")

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`tac` is a reverse `cat`

a command which produces output (stdout) and can be 'piped' `|` to another command.  
Linux/unix is extremely powerful with the pipe command.

So in this case the `tail` sends 16 lines to stdout and through the pipe to `tac` which reverses it.

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