We can use another form of variable expansion to select a specific substring, based on a specific character offset and length. Try typing in the following lines under bash.

可以根据特定字符偏移和长度，使用另一种形式的变量扩展，来选择特定子字符串。

youdao

Remember that UTF-8 encodes data an a variable-length format; the Unicode character at position 450 simply needed two bytes to be encoded in UTF-8.

记住 UTF-8 编码的数据是可变长的格式；450 处的 Unicode 字符在使用 UTF-8 进行编码时实际上只需要两个字节。

youdao

The description column is a variable-length character string, so it expects a string (which you indicate by enclosing the character data within single quotes).

description列是长度可变的字符串，所以它预计是一个字符串(通过将字符数据括在单引号中指明)。

youdao