is theere any function to extract login user id to server operating system, i tried $user but it returns value USER. server os is unix

I get $processinfo output only when exclusive connection is opened as shown below .

(_detail) CONNECT_UROUTER:1 activate "OSUSR"."GET_OSID"( PID )
(_detail) CONNECT_UROUTER:2 [-155] putmess "output is is %%PID" <——————- before exclusive connection opening
output is is
(_detail) CONNECT_UROUTER:3 [-155] putmess "in connect urouter – %%$$FUNC_ID, %%$$SERVER"
in connect urouter – rsm2app2, SMART2AP
(_detail) CONNECT_UROUTER:4 [-155] open "|%%$$FUNC_ID|%%$PINFO$|%%$$SERVER /ex", "$LOG/NET"
(_detail) CONNECT_UROUTER:5 putmess "status is %%$status"
status is 0
(_detail) CONNECT_UROUTER:6 if ($status < 0)
(_detail) CONNECT_UROUTER:10 endif
(_detail) CONNECT_UROUTER:11 activate "OSUSR"."GET_OSID"( PID ) <—————after exclusive connetion opening
(_detail) CONNECT_UROUTER:12 putmess "output is is %%PID"
output is is rsm2app2

code in osusr services
==================

operation get_osid
params
string vPID : inout
endparams
vPID = $processinfo("user")
end