unable to retrieve string from a big string with special symbols. Any help?

[indianhans]

Hi Wish to retrieve hammadahmad from below string. Below string contain html tag ( & a p o s ; ) without space.

• String = &a pos;hammadahmad&ap os; (service Active Directory)
• Current Regular Expression : | rex "Session login, user(?P/<USER/>.*?)logging in from machine"

Any help will be appreciated.

[sduff_splunk]

rex field=USERNAME "&apos;(?<user>\S+)&apos;"