Inserting blank lines 2

[screwloose]

Using either sed or awk, if I have a file that contains:

Jul 23 08:23:45 saturn
Jul 23 08:24:45 saturn
Jul 23 08:23:46 neptune
Jul 23 08:21:47 mercury
Jul 23 08:23:45 venus
Jul 23 08:32:45 venus
Jul 23 08:33:45 pluto
Jul 23 08:23:45 jupiter
Jul 23 08:23:45 jupiter
Jul 23 08:23:45 jupiter

And I want to insert a blank line AFTER each new instance of a hostname:

Jul 23 08:23:45 saturn
Jul 23 08:24:45 saturn

Jul 23 08:23:46 neptune

Jul 23 08:21:47 mercury

Jul 23 08:23:45 venus
Jul 23 08:32:45 venus

Jul 23 08:33:45 pluto

Jul 23 08:23:45 jupiter
Jul 23 08:23:45 jupiter
Jul 23 08:23:45 jupiter


Thanks!!

 

[CaKiwi]

Untested

{
if (hn!=$NF) {
if (NR > 1) print ""
hn = $NF
}
print
}

CaKiwi

 

[vgersh99]

inst != $NF { printf "\n"; inst=$NF}
1

vlad
+----------------------------+
| #include<disclaimer.h> |
+----------------------------+

 

[vgersh99]

<modesty>
great minds think alike!
</modesty>

vlad
+----------------------------+
| #include<disclaimer.h> |
+----------------------------+

 

[screwloose]

I aplogize that I made a mistake. There is text on the line after the hostname. Taking this into account, how would this change the awk syntax?

Thanks!
***********************************

Jul 23 08:23:45 saturn libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:24:45 saturn libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:23:46 neptune libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:21:47 mercury libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:23:45 venus libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:32:45 venus libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:33:45 pluto libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:23:45 jupiter libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:23:45 jupiter libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered
Jul 23 08:23:45 jupiter libcsa: [ID 702911 user.error] c2admin: RPC: Program not registered

 

[CaKiwi]

Still untested

{
if (hn!=$4) {
if (NR > 1) print ""
hn = $4
}
print
}

CaKiwi

 

[screwloose]

Thanks. Worked perfect.