attr|attribute -c|-create attr_name -p|-project [-f|-force]
-t|-type attr_type [-v|-value attr_value] project_spec...
attr|attribute -c|-create attr_name -t|-type attr_type
[-v|-value attr_value] [-f|-force] object_spec...
ccm attr -c attr_name -t type 和 ccm attr -c attr_name -f -t type 之间的区别在于,如果属性存在,那么不带 -force 选项的命令会失败。
ccm attr -c new_attr -type string driver.c