1.变量通过“ ”引号引起来
如下所示,可以得到结果为 is null
#!/bin/bash para1= if[! -n "$para1"] then echo "is null" else echo "not null" fi
2.直接通过变量判断:
如下所示,得到的记过为: is null
#!/bin/bash para1= if[!${para1}];then echo "is null" else echo "not null" fi
3.使用test判断
#!/bin/bash dmin= if test -z "$dmin" then echo "dmin is not set!" else echo "dmin is set !" fi
4.使用""判断
#!/bin/bash dmin= if [ "$dmin" = "" ] then echo "dmin is not set!" else echo "dmin is set !" fi