How to get process path on linux

$ps -eaf | grep pmon


oracle 24771 1 0 Aug14 ? 00:02:59 ora_pmon_INST1
oracle 28486 1 0 Sep05 ? 00:04:00 ora_pmon_INST2

$readlink -f /proc/24771/exe
/.../bin/oracle
$readlink -f /proc/28486/exe
/.../bin/oracle