Use following commands
AD_TOP=/u01/apps/[hostname]/apps/apps_st/appl/ad/12.0.0/
PATH=$AD_TOP/bin:$PATH
COMMON_TOP=/u01/apps/[hostname]/apps/apps_st/comn
INST_TOP=/u01/apps/[hostname]/inst/apps/[SID]_[hostname]
. /u01/apps/EBS12/inst/apps/[SID]_[hostname]/ora/10.1.2/[SID]_[hostname].env
APPL_TOP=/u01/apps/[hostname]/apps/apps_st/appl
. /u01/apps/[hostname]/apps/apps_st/appl/[SID]_[hostname].env
Where
Assumptions
Environment used for demonstration