-bash: [: @: binary operator expected

Question

all,

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"

then I got the error like above in the title:

-bash: [: @: binary operator expected

The error message in the last line is like below:

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

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, thanks very much for your quick reply.

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

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

Answer 1

well since my comment works, might as well post it in the answer section ;)

Use double "[["

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

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Answer 2

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

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

---

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

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