-bash：[：@：预期为二进制运算符 [英] -bash: [: @: binary operator expected

问题描述

全部，

我正在最后一行中检查文件中的错误信息，如果出现错误，我希望结果为是 。我的Shell脚本如下所示：

I am checking the error info in a file in the last line, I would like to have a "yes" result if there is an "Error". My shell script is like below:

[ $(tail -1 error.log | grep -E "Error") ] && echo "yes"

然后我在标题中得到了上面的错误：

then I got the error like above in the title:

-bash: [: @: binary operator expected

最后一行中的错误消息如下：

The error message in the last line is like below:

[aaa,bbb,ccc, Error.ddd @ ]

我认为这是因为错误消息的格式为[@]内容导致此错误。但是我不知道如何解决它。有谁知道如何处理此[@]问题。非常感谢

I think that is because of the the Error message, which has [ @ ] format content caused this error. But I do not know how to fix it. Is there any one knows how to process this [ @ ] problem. Thanks very much

@csiu，非常感谢您的快速回复。

@csiu, thanks very much for your quick reply.

此处的窍门是使用双 [，如下所示：

The trick here is to use double "[" as below:

 [[ $(tail -1 error.log | grep -E "Error") ]] && echo "yes"

推荐答案

除了@csiu的答案，不要完全不需要 test 命令。您可以根据grep的退出状态进行操作：

Additionally to @csiu's answer, don't need the test command at all. You can operate based on grep's exit status:

tail -1 error.log | grep -qE "Error" && echo yes

使用 -q 静音grep的输出。效率更高，因为一旦找到模式，grep就会立即退出。

Use -q to silence the output from grep. It's also more efficient because grep will exit immediately once the pattern is found.

由于我们只有一行输入，我们甚至不需要grep：

Since we only have one line of input, we don't even need grep:

[[ $(tail -1 error.log) == *Error* ]] && echo yes

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