shell 判断字符串长度是否为0

test.sh

#!/bin/bash
echo "enter the string:"
read filename
if test -z $filename ; then
echo "the length is 0"
else
echo "the length is not 0"
fi

执行

sudo chmod +x test.sh
./test.sh

输出

enter the string:

the length is 

执行

./test.sh

输出

enter the string:
sssssss
the length is not