test -n和test -z都为真的情况 [英] A case in which both test -n and test -z are true

问题描述

#! /bin/bash

echo "Please input 2 nums: "

read a b

if [ -z $b ]; then
        echo b is zero !
fi

if [ -n $b ]; then
        echo b is non-zero !
fi

当运行脚本时，仅输入1个数字，而另一个则保留为空，则b应该为空.但结果是同时打印了两个回声.

when run the script, only input 1 number, and leave the other empty, then b is supposed to be null. but the result is both echo is printed.

-laptop:~$ ./test.sh 
Pleaes input 2 nums: 
5 
b is zero !
b is non-zero !

b既为空又为非空?有人可以对此发表评论吗?谢谢！

b is both null and non-null ?! Could anyone comment on this ? Thanks !

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推荐答案

替换

if [ -z $b ]; then

使用

if [ -z "$b" ]; then

并在其他 if 条件下也进行同样的操作.

And do the same in the other if condition as well.

请参见 http://tldp.org/LDP/abs/html/testconstructs.html进行一些有趣的测试.

See http://tldp.org/LDP/abs/html/testconstructs.html for some interesting tests.

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