How to remove unwanted information after using grep using Linux commands

Question

I have a file that contains various different information in an unformatted way. I have been asked to create a list of all .com , .org and .net .de domain names referenced in the text. Each entry should only contain the domain.extension (stackexchange.com NOT http://www.stackexchange.com/index) and should only appear once in the list.

Here is a sample of the data:

230 User astalavista.com logged in.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls -la
227 Entering Passive Mode (212,254,194,163,2,188)
150 Opening BINARY mode data connection for 'file list'.
dr-x------   1 root users         4096 Jun  4 06:13 astalavista.com
226 Transfer complete.
ftp> cd astalavista.com
250 CWD command successful.
ftp> ls -la
227 Entering Passive Mode (212,254,194,163,2,189)
150 Opening BINARY mode data connection for 'file list'.
-rw-rw-rw-   1 astalavista.com users     23410936878 Apr 29 22:10 
09-04-28-astacom_full.tar
-rw-rw-rw-   1 astalavista.com users     20617651590 Apr 29 14:18 
09-04-28-astacom_full.tar.bz2
-rw-rw-rw-   1 astalavista.com users        88287111 Apr 29 15:57 
09-04-29-astacom_sql_full.sql.tar.bz2
-rw-rw-rw-   1 astalavista.com users     26413034040 May  2 00:21 
09-05-01-astacom-Public_HTML.tar
rw-rw-rw-   1 astalavista.com users       277843549 May  1 17:29 
09-05-01-astacom-SQL_Dump.tar
[snip]
226 Transfer complete.
ftp> mdelete *
ftp> ls -la
227 Entering Passive Mode (212,254,194,163,2,193)
150 Opening BINARY mode data connection for 'file list'.
226 Transfer complete.
ftp>

So far I have used egrep to find all the occurences of .com , .net , .org , .de .

egrep '\.\de|\.\com|\.\org|\.\net' hacklog1 

I've been trying to use sed to remove the rest of the unwanted data to no avail. Could someone suggest a command syntax to help me.

Answer 1

Try something like:

egrep -o '[0-9A-Za-z_-]+\.(com|org|net|de)\b'

It should be fairly easy to tune the characters allowed before the TLD and the list of recognized TLDs to your liking.