Userhost

Do you mean:

• The userhost command, /userhost [options] [nicknames...], which requests username/hostname information and displays results or invokes a callback? Callback requests can use cached results synchronously unless forced through the server path.
• The userhost function, $userhost([nicknames...]), which returns current sender information or reads local channel caches without sending a request?

With no arguments, the function reads the current message sender's user@host context; outside suitable message processing it is normally empty. With nickname arguments, unknown cached addresses are represented as <UNKNOWN>@<UNKNOWN>. The command is the appropriate interface for requesting fresh server information, but it does not synchronously return that reply as a function value.

Userhosts are server-supplied text and may contain cloaked hostnames rather than IP addresses. See the selected page for callback timing, flags, cache limitations, and server-dependent results.

Source references

• source/who.c: command request queue, cache-assisted callbacks, and reply handling.
• source/functions.c: sender-context and nickname-cache function forms.
• source/names.c: channel userhost cache.