Stable sort

Shell Programming and Scripting
1

if i use this pattern: last -R

I get this:

vsetm7am pts/2 Thu Aug 21 14:33 still logged in
vsetm7am pts/0 Thu Aug 21 13:21 still logged in
hoffp7am pts/2 Thu Aug 21 11:40 - 11:41 (00:00)
vsetm7am pts/1 Thu Aug 21 11:11 still logged in
vsetm7am pts/0 Thu Aug 21 09:51 - 13:21 (03:30)
valcj4am pts/2 Thu Aug 21 02:06 - 02:06 (00:00)
vsetm7am pts/0 Thu Aug 21 00:40 - 03:01 (02:20)
vsetm7am pts/1 Wed Aug 20 21:03 - 03:01 (05:58)
vsetm7am pts/0 Wed Aug 20 20:54 - 21:18 (00:23)
vsetm7am pts/1 Wed Aug 20 17:17 - 21:03 (03:45)
vsetm7am pts/0 Wed Aug 20 13:12 - 20:40 (07:27)
valcj4am pts/0 Wed Aug 20 02:05 - 02:06 (00:00)
vsetm7am pts/0 Tue Aug 19 21:02 - 21:40 (00:38)
vsetm7am pts/1 Tue Aug 19 17:32 - 17:53 (00:21)
vsetm7am pts/2 Tue Aug 19 12:52 - 20:11 (07:18)
vsetm7am pts/1 Tue Aug 19 12:21 - 13:08 (00:47)
vsetm7am pts/0 Tue Aug 19 12:21 - 20:11 (07:49)
valcj4am pts/2 Tue Aug 19 02:05 - 02:06 (00:00)
vsetm7am pts/2 Mon Aug 18 19:26 - 19:26 (00:00)
vsetm7am pts/1 Mon Aug 18 19:23 - 03:13 (07:49)
vsetm7am pts/2 Mon Aug 18 19:22 - 19:22 (00:00)
vsetm7am pts/2 Mon Aug 18 19:15 - 19:15 (00:00)
vsetm7am pts/2 Mon Aug 18 19:15 - 19:15 (00:00)
vsetm7am pts/1 Mon Aug 18 18:40 - 19:23 (00:42)
vsetm7am pts/0 Mon Aug 18 18:40 - 03:04 (08:24)
vsetm7am pts/1 Mon Aug 18 18:37 - 18:40 (00:02)
vsetm7am pts/2 Mon Aug 18 18:33 - 18:40 (00:06)
vsetm7am pts/2 Mon Aug 18 18:26 - 18:26 (00:00)
vsetm7am pts/1 Mon Aug 18 18:25 - 18:33 (00:08)
vsetm7am pts/0 Mon Aug 18 18:20 - 18:40 (00:19)
vsetm7am pts/2 Mon Aug 18 18:08 - 18:19 (00:11)
vsetm7am pts/2 Mon Aug 18 18:05 - 18:05 (00:00)
vsetm7am pts/0 Mon Aug 18 17:44 - 18:19 (00:35)
vsetm7am pts/1 Mon Aug 18 15:46 - 18:19 (02:33)
vsetm7am pts/1 Mon Aug 18 15:45 - 15:46 (00:00)
vsetm7am pts/0 Mon Aug 18 12:21 - 17:44 (05:22)
valcj4am pts/0 Mon Aug 18 02:02 - 02:02 (00:00)
vsetm7am pts/0 Sun Aug 17 12:51 - 22:30 (09:38)
kavkm2am pts/0 Sun Aug 17 09:39 - 09:39 (00:00)
valcj4am pts/0 Sun Aug 17 02:05 - 02:06 (00:00)
tutan4am pts/0 Sat Aug 16 12:14 - 12:17 (00:03)
mlejj5am pts/0 Sat Aug 16 12:00 - 12:00 (00:00)
valcj4am pts/0 Sat Aug 16 02:05 - 02:06 (00:00)
kotrj7am pts/0 Fri Aug 15 17:31 - 17:50 (00:19)
valcj4am pts/0 Fri Aug 15 02:05 - 02:05 (00:00)
valcj4am pts/0 Thu Aug 14 02:05 - 02:06 (00:00)
valcj4am pts/0 Wed Aug 13 02:05 - 02:06 (00:00)
valcj4am pts/0 Tue Aug 12 02:05 - 02:06 (00:00)
mlejj5am pts/0 Mon Aug 11 12:44 - 12:53 (00:09)
valcj4am pts/0 Mon Aug 11 02:05 - 02:06 (00:00)
valcj4am pts/0 Sat Aug 9 02:06 - 02:06 (00:00)
valcj4am pts/0 Thu Aug 7 02:05 - 02:05 (00:00)
suskm3am tty11 Wed Aug 6 16:43 - 16:49 (00:05)
valcj4am pts/0 Wed Aug 6 02:05 - 02:05 (00:00)
valcj4am pts/0 Tue Aug 5 02:05 - 02:05 (00:00)
valcj4am pts/0 Mon Aug 4 02:05 - 02:05 (00:00)
suflp4am pts/0 Sun Aug 3 21:12 - 22:52 (01:39)
suflp4am pts/0 Sun Aug 3 21:07 - 21:10 (00:02)
suflp4am pts/0 Sun Aug 3 13:39 - 14:20 (00:41)
valcj4am pts/1 Sun Aug 3 02:05 - 02:05 (00:00)
valcj4am pts/1 Sat Aug 2 02:04 - 02:05 (00:00)
suskm3am tty11 Fri Aug 1 11:42 - 12:31 (00:49)

When I use pattern like this: last -R | sort -s -t " " -k 1

I get this output:

hoffp7am pts/2 Thu Aug 21 11:40 - 11:41 (00:00)
kavkm2am pts/0 Sun Aug 17 09:39 - 09:39 (00:00)
kotrj7am pts/0 Fri Aug 15 17:31 - 17:50 (00:19)
mlejj5am pts/0 Mon Aug 11 12:44 - 12:53 (00:09)
mlejj5am pts/0 Sat Aug 16 12:00 - 12:00 (00:00)
suflp4am pts/0 Sun Aug 3 13:39 - 14:20 (00:41)
suflp4am pts/0 Sun Aug 3 21:07 - 21:10 (00:02)
suflp4am pts/0 Sun Aug 3 21:12 - 22:52 (01:39)
suskm3am tty11 Fri Aug 1 11:42 - 12:31 (00:49)
suskm3am tty11 Wed Aug 6 16:43 - 16:49 (00:05)
tutan4am pts/0 Sat Aug 16 12:14 - 12:17 (00:03)
valcj4am pts/0 Fri Aug 15 02:05 - 02:05 (00:00)
valcj4am pts/0 Mon Aug 4 02:05 - 02:05 (00:00)
valcj4am pts/0 Mon Aug 11 02:05 - 02:06 (00:00)
valcj4am pts/0 Mon Aug 18 02:02 - 02:02 (00:00)
valcj4am pts/0 Sat Aug 9 02:06 - 02:06 (00:00)
valcj4am pts/0 Sat Aug 16 02:05 - 02:06 (00:00)
valcj4am pts/0 Sun Aug 17 02:05 - 02:06 (00:00)
valcj4am pts/0 Thu Aug 7 02:05 - 02:05 (00:00)
valcj4am pts/0 Thu Aug 14 02:05 - 02:06 (00:00)
valcj4am pts/0 Tue Aug 5 02:05 - 02:05 (00:00)
valcj4am pts/0 Tue Aug 12 02:05 - 02:06 (00:00)
valcj4am pts/0 Wed Aug 6 02:05 - 02:05 (00:00)
valcj4am pts/0 Wed Aug 13 02:05 - 02:06 (00:00)
valcj4am pts/0 Wed Aug 20 02:05 - 02:06 (00:00)
valcj4am pts/1 Sat Aug 2 02:04 - 02:05 (00:00)
valcj4am pts/1 Sun Aug 3 02:05 - 02:05 (00:00)
valcj4am pts/2 Thu Aug 21 02:06 - 02:06 (00:00)
valcj4am pts/2 Tue Aug 19 02:05 - 02:06 (00:00)
vsetm7am pts/0 Mon Aug 18 12:21 - 17:44 (05:22)
vsetm7am pts/0 Mon Aug 18 17:44 - 18:19 (00:35)
vsetm7am pts/0 Mon Aug 18 18:20 - 18:40 (00:19)
vsetm7am pts/0 Mon Aug 18 18:40 - 03:04 (08:24)
vsetm7am pts/0 Sun Aug 17 12:51 - 22:30 (09:38)
vsetm7am pts/0 Thu Aug 21 00:40 - 03:01 (02:20)
vsetm7am pts/0 Thu Aug 21 09:51 - 13:21 (03:30)
vsetm7am pts/0 Thu Aug 21 13:21 still logged in
vsetm7am pts/0 Tue Aug 19 12:21 - 20:11 (07:49)
vsetm7am pts/0 Tue Aug 19 21:02 - 21:40 (00:38)
vsetm7am pts/0 Wed Aug 20 13:12 - 20:40 (07:27)
vsetm7am pts/0 Wed Aug 20 20:54 - 21:18 (00:23)
vsetm7am pts/1 Mon Aug 18 15:45 - 15:46 (00:00)
vsetm7am pts/1 Mon Aug 18 15:46 - 18:19 (02:33)
vsetm7am pts/1 Mon Aug 18 18:25 - 18:33 (00:08)
vsetm7am pts/1 Mon Aug 18 18:37 - 18:40 (00:02)
vsetm7am pts/1 Mon Aug 18 18:40 - 19:23 (00:42)
vsetm7am pts/1 Mon Aug 18 19:23 - 03:13 (07:49)
vsetm7am pts/1 Thu Aug 21 11:11 still logged in
vsetm7am pts/1 Tue Aug 19 12:21 - 13:08 (00:47)
vsetm7am pts/1 Tue Aug 19 17:32 - 17:53 (00:21)
vsetm7am pts/1 Wed Aug 20 17:17 - 21:03 (03:45)
vsetm7am pts/1 Wed Aug 20 21:03 - 03:01 (05:58)
vsetm7am pts/2 Mon Aug 18 18:05 - 18:05 (00:00)
vsetm7am pts/2 Mon Aug 18 18:08 - 18:19 (00:11)
vsetm7am pts/2 Mon Aug 18 18:26 - 18:26 (00:00)
vsetm7am pts/2 Mon Aug 18 18:33 - 18:40 (00:06)
vsetm7am pts/2 Mon Aug 18 19:15 - 19:15 (00:00)
vsetm7am pts/2 Mon Aug 18 19:15 - 19:15 (00:00)
vsetm7am pts/2 Mon Aug 18 19:22 - 19:22 (00:00)
vsetm7am pts/2 Mon Aug 18 19:26 - 19:26 (00:00)
vsetm7am pts/2 Thu Aug 21 14:33 still logged in
vsetm7am pts/2 Tue Aug 19 12:52 - 20:11 (07:18)

And the question is why the stable sort doesn't keep lines with "still logged in" at the beginning of the output of a given name? It should sort output only with respect to first column and still the second column seems to be sorted too.

Thank you!

2 
 -k keydef          The keydef argument is a restricted  sort
                        key  field definition. The format of this
                        definition is:

                          -k field_start [type] [,field_end [type] ]
.
.
.
                        A missing field_end means the last
                        character of the line.

So you are sorting on everything.

3

Thank you!

So that the right pattern is:

last -R | sort -s -t " " -k 1,1