bash 使用参数和返回值在bash中执行命令
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Execute command in bash with parameter and return value
提问by Disco
I have the following script to check if a NFS mount is currently mounted on the server :
我有以下脚本来检查服务器上当前是否安装了 NFS 安装：
#!/bin/bash
$targetserver=192.168.3.1
commandline="mount | grep '$targetserver' | wc -l"
checkmount=`$commandline`
if [ $checkmount == "1" ]; then
echo "Mounted !"
else
echo "Not mounted"
fi
But it seems that my checkmount is not returning anything.
但似乎我的 checkmount 没有返回任何东西。
What am I missing here ?
我在这里错过了什么？
回答by jgr
This should work better.
这应该工作得更好。
#!/bin/bash
targetserver="192.168.3.1"
commandline=$(mount | grep "$targetserver" | wc -l)
if [ $commandline -gt 0 ]; then
echo "Mounted !"
else
echo "Not mounted"
fi
You could shorten it down though, using $?, redirection and control operators.
不过，您可以使用$?、重定向和控制运算符缩短它。
targetserver="192.168.3.1"
mount | grep "$targetserver" > /dev/null && echo "mounted" || echo "not mounted"
Depending on system grep /etc/mtabdirectly might be a good idea too. Not having to execute mountwould be cleaner imho.
grep /etc/mtab直接依赖于系统也可能是一个好主意。不必执行mount会更清洁恕我直言。
Cheers!
干杯!
回答by plundra
I'd maybe do this, or just but the content of the function directly in if, if you just use it in one place.
我可能会这样做，或者只是直接在 中的函数内容if，如果你只是在一个地方使用它。
nfsismounted() {
mount | grep -qm1 "":
}
q = quiet (we just want the return code), m1 = quit on first match.
q = 安静（我们只想要返回码），m1 = 在第一场比赛时退出。
And use it as such:
并使用它：
if nfsismounted 192.168.0.40; then
echo "Mounts found"
else
echo "Not mounts"
fi
A side note on the code in your question, you don't test with == in the shell, just =. == Will break on, for example, dash which is /bin/sh in Debian/Ubuntu since a while.
关于您问题中代码的旁注，您不在 shell 中使用 == 进行测试，而只是使用 =。== 将打破，例如，破折号，它是 Debian/Ubuntu 中的 /bin/sh 一段时间。
Edit: For added portability (non-GNU grep), remove the flags on grepand > /dev/null. Tests were done on bash/dash/ksh
编辑：为了增加可移植性（非 GNU grep），删除grep和> /dev/null. 测试是在 bash/dash/ksh 上完成的
