Code:
ldapsearch -x -D cn=Manager,dc=domain,dc=com -W -y .passwd.txt -L "(&(objectclass=person)(!(pwdChangedTime=*)))" userPassword
| sed '/dn: /a\changetype: modify\nreplace: userPassword'
| ldapmodify -x -D cn=Manager,dc=domain,dc=com -W -y .passwd.txt