Bash 警告 - 预期的参数
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Bash warning - argument expected
提问by user986959
The bash script bellow takes a MAC address as a variable and finds the IP address corresponding to this MAC address.
下面的 bash 脚本将 MAC 地址作为变量，并找到该 MAC 地址对应的 IP 地址。
#!/bin/bash
read address
OUTPUT="$(nmap -sn -n /IP_ADDRESS_RANGE/ | grep -B 2 "$address" |
grep -e ^.*[0-9].[0-9].[0-9].[0-9] | awk '{print substr(find.sh: 7: [: =: argument expected
/IP_ADDRESS/
**:**:**:**:*:* **:**:**:**:**:** 0806 42: arp reply 192.168.1.1 is-at **:**:**:**:*:*
,22)}')"
if [ ${OUTPUT} = ""]; then
echo "not found"
else
echo "${OUTPUT}"
arpspoof -i wlan1 -t ${OUTPUT} /GATEWAY/
fi
Although it works fine and as expected I get a warning when I execute it and I want to find out how to fix it. The output I get after I enter the MAC address:
虽然它工作正常并且按预期执行，但我在执行它时收到警告，我想找出如何修复它。输入MAC地址后得到的输出：
if [ ${OUTPUT} = "" ]
^--- Required
回答by that other guy
There are multiple errors. shellcheckfinds the most obvious ones:
有多个错误。shellcheck找到最明显的：
First, you are missing a space here:
首先，您在这里缺少一个空格：
if [ "${OUTPUT}" = "" ]
^-- Here -^
Second, you're missing required quoting:
其次，您缺少必需的引用：
[ -z "${OUTPUT}" ]
This should be sufficient to get rid of the error you're seeing.
这应该足以消除您看到的错误。
Here are the other problems:
以下是其他问题：
Your regex tries to match an ipv4 address, but instead matches 8 character strings where every other character is a digit.
The regex is unquoted, so it could also accidentally match files in the directory and break
grepYou run the script with
sh yourscript. This only works forshscripts. To runbashscripts, usebash yourscript.
您的正则表达式尝试匹配 ipv4 地址，但匹配 8 个字符串，其中每个其他字符都是数字。
正则表达式未加引号，因此它也可能不小心匹配目录中的文件并中断
grep您使用
sh yourscript. 这仅适用于sh脚本。要运行bash脚本，请使用bash yourscript.
回答by Droopy4096
why not use:
为什么不使用：
[ "z${OUTPUT}" = "z" ]
instead? people have also use an ugly trick like this:
反而？人们还使用了这样一个丑陋的技巧：
##代码##to catch empty strings
捕捉空字符串
