It will not return an error to standard output if the file is not found. One way to test the return of the command is to use substitution, like shown in Listing 8.
即使找不到文件，它也不会向标准输出返回错误。
Because the traditional calibrating method is not suitable for testing optical electric current transformer, a novel test system is designed based on the IEC standard and error analysis theory.
鉴于传统的电流互感器测试方法已经不适于校验新型的电流互感器，依据IEC标准和误差分析理论，提出了光电电流互感器的测试和校验方法。
A new tool that can test the clock base frequency error of energy measuring devices and provide GPS standard time to calibrate real-time clock was introduced in this paper.
介绍了一种用来测量电能计量装置的时钟基频误差，并提供GPS标准时间以校准其实时时钟的新型工具。
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