The earliest versions were created in 2.9 BSD as a convenience form for who am i, the Berkeley Unix who command's way of printing just the logged in user's identity.

The command is available as a separate package for Microsoft Windows as part of the GnuWin32 project[3] and the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities.

[4] On Intel iRMX 86 this command lists the currents user's identification and access rights.

[7] The ReactOS version was developed by Ismael Ferreras Morezuelas and is licensed under the GPLv2.

It also outputs the current connections to which server the workstation is attached with which username.