49.11. $userID

$userID returns the user ID of the current user, if possible. The form of the user ID is described in the relevant part of the MAINSAIL System-Specific User's Guides.

If the operating system does not provide a user ID, a prompt is written to logFile and a user name read from cmdFile. After the user is prompted once, the user ID is remembered and returned on all subsequent calls to $userID within the same process.

The only valid ctrlBits bits are $login and errorOK.

If errorOK is set, the null STRING is returned without dialogue if the user ID is unavailable.

Some systems distinguish between a login user ID (the user ID under which the current user logged in) and the effective user ID (if the user ID was somehow changed during the login session). If $login is specified, the login user ID is returned, if available; otherwise, the effective user ID is returned, if available. The relevant part of the MAINSAIL System-Specific User's Guides for each system where $login makes a difference describes its effect.

It is advisable always to check $userID's return for the null STRING, since it is fairly common for either the effective user ID or the login user ID to be unavailable, depending on the operating system.