See the environment variables for a process when it was started

pargs -e <PID>

Example:

ps -ef | grep tnslsnr
  oracle 20083 11285   0   Dec 30 ?          17:22
/apps/oracle/product/10.2.0/db_1/bin/tnslsnr LISTENER -inherit

pargs -e 20083
20083:  /apps/oracle/product/10.2.0/db_1/bin/tnslsnr LISTENER -inherit
envp[0]: _=/apps/oracle/product/10.2.0/db_1/bin/lsnrctl
envp[1]: MANPATH=/usr/share/man
envp[2]: SSH_TTY=/dev/pts/1
envp[3]:
PATH=/usr/ccs/bin:/usr/bin:/usr/sbin:/usr/ucb:/usr/proc/bin:/usr/local/bin:/usr/bin/nsr:/opt/soe/local/bin:/apps/oracle/local/bin:/apps/oracle/product/10.2.0/db_1/bin
envp[4]: ORACLE_BASE=/apps/oracle
envp[5]: AWK=/usr/bin/nawk
envp[6]: ORACLE_PATH=.:/apps/oracle/local/bin
envp[7]: EDITOR=vi
envp[8]: LOGNAME=oracle
envp[9]: MAIL=/usr/mail/oracle
envp[11]: USER=oracle
envp[12]: TNS_ADMIN=/apps/oracle/net/admin
envp[13]: ORA_NLS10=/apps/oracle/product/10.2.0/db_1/nls/data
envp[15]: SHELL=/bin/ksh
envp[16]: ORATAB=/var/opt/oracle/oratab
envp[17]: HOME=/apps/oracle
envp[20]: TERM=xterm
envp[21]: ORACLE_HOME=/apps/oracle/product/10.2.0/db_1
envp[22]: OS_TYPE=SunOS
envp[23]: PWD=/apps/oracle
envp[24]: TZ=Australia/Victoria
envp[25]: ORA_NET2_DESC=5,8