1. str="we are not the man who would just accept everything!"
   2022 $ echo ${#str}
   52
2. str="we are not the man who would just accept everything! "
   2020 $ echo ${#str}
   53

对比发现string的末尾空格是会被算长度的

3. 2008 $ echo ${str:2}
   are not the man who would just accept everything!
   2013 $ echo ${str:2}|wc -c
   50

4. 2011 $ echo ${str:3}
   are not the man who would just accept everything!
   2012 $ echo ${str:3}|wc -c
   50

对比发现字符串截取时第一位是空格的话echo默认去掉了空格。

5. 2014 $ str="we are not the man who would just accept everything! "
   [root@mc-adn-deploy-172-17-0-17@~@17:02:23]
   2015 $ echo ${str:2}|wc -c
   50

对比发现字符串末尾的空格在字符串被截取时也被移除了，所以长度和末尾没有空格时一样——这时因为用了wc -c ？
是的。请看：
2028 $ str2=${str:2}
2029 $ echo ${#str2}
54
此处将截取的字符串内容保存再算长度，得到的就是包含空格的长度。

echo是很好的去掉字符串开始和末尾的空格的一种方式！