The character position of the start of each field is specified by a directory.
每个栏位起始的字元位置由该目录规定。
Use implicit the defect of the file depends on, be in temporarily in the position that file directory is in, see less than taking up of file system big temporarily file.
使用隐含文件的缺点在于，在临时文件目录所在的位置中，看不到占用了文件系统的大临时文件。
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