SQL> ! ps -ef | grep pmon
  oracle  8311     1  0  Apr 18  ?         1:41 ora_pmon_HC890TST
  oracle 16750     1  0  Mar 16  ?         3:41 ora_pmon_HC890DEV
  oracle 17657     1  0  Mar 16  ?         3:37 ora_pmon_HC890CFG
  oracle 17430     1  0  Mar 16  ?         3:41 ora_pmon_HC890UAT
  oracle 18024     1  0  Mar 16  ?         3:41 ora_pmon_HC890DMO
  oracle  7653  7651  1 16:57:35 pts/1     0:00 grep pmon
  oracle  7651  6622  0 16:57:35 pts/1     0:00 /usr/bin/sh -c  ps -ef | grep pmon

SQL> echo $ORACLE_SID
SP2-0734: unknown command beginning "echo $ORAC..." - rest of line ignored.
SQL> !echo $ORACLE_SID
HC890TST

SQL> shutdown immediate;
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
HP-UX Error: 2: No such file or directory
SQL>