有个问题很有意思！

Iambitious

str="08";integer=$(($str+1));echo $integer
出现错误bash: 08: value too great for base (error token is "08")
感觉很奇怪，于是测试了一些其他的值
str="07"正确，06 05 04 03 02 01都正确
str="349938" 正确，开头不为0的数正确
str="016"错误输出15
str="017"错误输出16
str="0127"错误输出88
str="0128"bash: 08: value too great for base (error token is "0128")
发现任何出现8以及9的以0开头的数都出现此错误，恍然大悟，原来以0开头的数，bash会把其解释成8进制的数。

troll

Constants with a leading 0 are interpreted as octal numbers. A leading 0x or 0X denotes hexadecimal. Otherwise, numbers take the form [base#]n, where base is a decimal number between 2 and 36 representing the arithmetic base, and n is a number in that base. If base is omitted, then base 10 is used.

bash手册

Iambitious

thanks a lot这回终于彻底明白了。