I'm trying to parse my /var/log/secure file so that I can close down my system with iptables after repeated incorrect logins. I can extract the correct IP address to a file, but the file (depending on the number of login attempts) lists the same address multiple times. Is there any way to either 1) only add a line of text to a file if that line of text isn't already present... or 2) parse a file with a list of IP addresses and come up with a list of each IP only one time? Or to put that another way:

aaa.bbb.ccc.ddd
aaa.bbb.ccc.ddd
aaa.bbb.ccc.ddd
aaa.bbb.ccc.ddd
aaa.bbb.ccc.ddd
aaa.bbb.ccc.ddd
eee.fff.ggg.hhh
eee.fff.ggg.hhh
eee.fff.ggg.hhh
eee.fff.ggg.hhh

[magic happens here]

aaa.bbb.ccc.ddd
eee.fff.ggg.hhh

Thank you kindly.
ink

Just add a -u to the sort (that you're presumably
doing)...


Cheers,
Tink