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I wrote this simple awk program:

last -n 10 | awk'{print "username: " $1}'

I was surprised when i got the following output:

> username: someUsername1
> username: someUsername2
> username: someUsername3
> ...
> username: someUsername10
> username: 
> username: wtmp

using last -n 10 | wc -l i learned that the last command return two more lines than the number i gave it (the output was 12)

I checked in man last and didn't find anything about those two extra lines or how to get rid of them.

what are those blank and 'wtmp' lines? and how can i ignore them? (maybe in the side of the awk?)

Thanks!

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A generic solution which will work everywhere, and when there are fewer than ten entries in the login database, is to trim the last two lines:

last -n 10 | head -n -2 | awk'{print "username: " $1}'

Recent versions of util-linux (2.30.2 and later) allow the wtmp line to be dropped:

last -n 10 --time-format=notime | awk'{print "username: " $1}'
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If I run last without any arguments, I get the following output:

wtmp begins Fri Sep 22 18:15:02 2017

And an empty line before it. This is the date from which the logins are recorded.

You can get rid of this using head.

last | head -n10
  • In fact, you may drop all options to last as you're limiting the number of lines with head anyway. Also, 10 lines is the default for head (and tail). – Kusalananda Nov 5 '18 at 11:12
  • Good point. Will edit my answer to include this. – Panki Nov 5 '18 at 11:14
  • This fails when there are fewer than ten entries in wtmp. – Stephen Kitt Nov 5 '18 at 11:17
  • thanks! but Stephan solution is cover all cases – Z E Nir Nov 5 '18 at 11:22

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