typeset的用法，用-开启各个选项，用+关闭选项。
-L Left justify and remove blank spaces
-R Right justify and to fill with leading blanks
-Zn Right justify to n length and fill with leading zeros if the first
non-blank character is a digit
-i Variable is an integer
-l Convert uppercase characters to lowercase characters
-u Convert lowercase characters to uppercase characters
-x Automatically export this variable