shell判断一个变量是否为空方法总结

#!/bin/shpara1=if [ ! -n "$para1" ]; then  echo "IS NULL"else  echo "NOT NULL"fi

#!/bin/shpara1=if [ ! $para1 ]; then  echo "IS NULL"else  echo "NOT NULL"fi

#!/bin/shdmin=if test -z "$dmin"then  echo "dmin is not set!"else    echo "dmin is set !"fi

#!/bin/sh dmin=if [ "$dmin" = "" ]then  echo "dmin is not set!"else    echo "dmin is set !"fi