sed substring from incoming packet

Question

String I want to sed i get from incoming sniffered packet... I want to get substring from string, f.e.

INVITE sip:[email protected]:5060 SIP/2.0

Using sed I would like to extract substring.
Substring is between sip: and @ ... So for my example, I need to get

18455845013

Answer 1

Input file

$ cat foo.txt
INVITE sip:[email protected]:5060 SIP/2.0

Result

$ sed 'y/:@/\r\n/;P;d' foo.txt
18455845013

• change : to \r
• change @ to \n
• print up to first newline
• delete pattern space