at 명령 사용 시 나타나는 경고 메시지 제거 [중복]

나는 bash 구성 파일에서 명령을 사용하여 at매 시간마다 시간을 에코하여 시간을 상기시켜 주지만 이제 명령줄을 열면 다음과 같은 성가신 경고가 많이 깜박입니다.

warning: commands will be executed using /bin/sh
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job 251 at Wed Aug 31 10:00:00 2016
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job 252 at Wed Aug 31 11:00:00 2016
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job 253 at Wed Aug 31 12:00:00 2016
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job 254 at Wed Aug 31 13:00:00 2016
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job 255 at Wed Aug 31 14:00:00 2016
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job 256 at Wed Aug 31 15:00:00 2016
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job 257 at Wed Aug 31 16:00:00 2016
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job 258 at Wed Aug 31 17:00:00 2016
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job 259 at Wed Aug 31 18:00:00 2016
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job 260 at Wed Aug 31 19:00:00 2016
warning: commands will be executed using /bin/sh
job 261 at Wed Aug 31 20:00:00 2016
warning: commands will be executed using /bin/sh
job 262 at Wed Aug 31 21:00:00 2016
warning: commands will be executed using /bin/sh
job 263 at Wed Aug 31 22:00:00 2016
warning: commands will be executed using /bin/sh
job 264 at Wed Aug 31 23:00:00 2016

내가 실행하려는 명령은 예입니다.

echo "midnight" | at 00:00

이러한 경고를 어떻게 제거할 수 있나요?

at참고: 이는 " 명령을 실행하기 위해 /bin/sh를 사용한다는 경고가 표시되는 이유는 무엇입니까? 다른 쉘을 원하면 어떻게 됩니까?"라는 질문과 다릅니다. 경고를 제거하는 방법 및 쉘에 대한 정보를 알고 싶지 않습니다.