删除字符串的命令如下：
${string#substring} #删除string开头处与substring匹配的最短子串
${string##substring} #删除string开头处与substring匹配的最长子串
echo $another_string
20091114 Reading Hadoop
echo ${another_string#2*1}
114 Reading Hadoop
echo ${another_string##2*1}
4 Reading Hadoop
删除字符串还有从结尾开始删除的，命令如下：
${string%substring} #删除string结尾处与substring匹配的最短子串
${string%%substring} #删除string结尾处与substring匹配的最长子串
echo ${another_string%a*p}
20091114 Reading H
echo ${another_string%%a*p}
20091114 Re