作用：
- 检查元素文件语法；
- 转换格式、支持xml binary json；
- 插入key－value；
- 打印内部信息；
详细解释：
-lint check the property list files for syntax errors
-convert fmt rewrite property list files in format
fmt is one of: xml1 binary1 json
-insert keypath -type value insert a value into the property list before writing it out
keypath is a key-value coding key path, with one extension:
a numerical path component applied to an array will act on the object at that index in the array
or insert it into the array if the numerical path component is the last one in the key path
type is one of: bool, integer, float, date, string, data, xml, json
-bool: YES if passed "YES" or "true", otherwise NO
-integer: any valid 64 bit integer
-float: any valid 64 bit float
-string: UTF8 encoded string
-date: a date in XML property list format, not supported if outputting JSON
-data: a base-64 encoded string
-xml: an XML property list, useful for inserting compound values
-json: a JSON fragment, useful for inserting compound values
value YES, NO, a number, a date, or a base-64 encoded blob of data
-p print property list in a human-readable fashion
There are some additional optional arguments that apply to the -convert, -insert, -remove, -replace, and -extract verbs:
-s be silent on success
-o path specify alternate file path name for result;
the -o option is used with -convert, and is only
useful with one file argument (last file overwrites);
the path '-' means stdout
-e extension specify alternate extension for converted files
-r if writing JSON, output in human-readable form
-- specifies that all further arguments are file names