The read function returns the number of bytes read (up to the maximum that you specify), -1 on error, or zero if the end of the file has been reached.

read函数返回读取的字节数（最高为您指定的最大值）；或者 -1，表示错误；或者0，如果已经到达文件末尾。

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This count can match the expected number of items or be less (even zero) due to a matching failure, a reading error, or the reach of the end-of-file.

这个数可以匹配项目的预期数量或是少(甚至为零)由于匹配失败，读取错误，或文件结束达到。

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This count can match the expected number of items or be less (even zero) due to a matching failure, a reading error, or the reach of the end-of-file.

这个数可以匹配项目的预期数量或是少(甚至为零)由于匹配失败，读取错误，或文件结束达到。

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