https://www.cnblogs.com/37yan/p/6962563.html
caution!!! if should be end with fi
caution!!! there should be a space between [ and ! , also between 1 and ]
if [ ! $# -eq 1 ];then
#!/bin/bash # 判断传入的参数的个数是不是一个 if [ ! $# -eq 1 ];then echo param error! exit 1 fi # 判断目录是不是已经存在，如果不存在则创建，存在则输出“dir exist” dirname=$1 echo "the dir name is $dirname" if [ ! -d $dirname ];then mkdir $dirname else echo dir exist fi
原文：https://www.cnblogs.com/zealousness/p/9483523.html