Current Principal (User) Name (_u)
The _u convenience variable holds the current simple principal name. The dcecp program sets this variable from the login context inherited from the parent process. You can change its value by performing another login operation. Setting it using set generates an error.
dcecp> puts $_u
cell_admin
A practical use of this variable could be in scripts that test for a certain DCE identity before proceeding. On finding an incorrect identity, scripts could prompt for the necessary identity information and perform a dce_login operation.
See the cell name variable description in Current Cell Name (_c) for information about composing fully qualified principal names