SQL> alter user ... identified  by newpassword;

# also try "whoami" it may work better for you.
who am i | read usr junk

   while (true)
   do
      echo "Change Oracle password for \"$usr\" ? (y/n)"
      read ans
      case $ans in
      Y*|y*)   break;;
      N*|n*)   exit 0;;
      esac
   done

#read passwd twice and if same value entered
# then reset...

## you need to prompt for PASS etc here...

# check passwd for unwanted characters etc...
# untested

## escape the $...
BADCHAR=`echo $PASS | egrep '=|\$|&|%|#|@| |_' | wc -l`
if [ $BADCHAR -gt 0 ]; then
  echo "ERROR. Invalid characters found in password(@,_,space etc)"
  exit 1
fi

# check passwd length too...
## X=my_passwd
## LEN=`echo $X | wc -c` 
## if [ $LEN -lt 6 ]; then
##   echo "ERROR. Password too short.. 



sqlplus ... <<EOF
-- reset passwd for $usr
EOF
RV=$?

# test RV to see of 0 (success) or not...

#!/bin/ksh