以下语法的含义是:fstream myFile("test.txt"，ios :: in | ios :: out | ios :: trunc); [英] What is the meaning of following syntax:: fstream myFile("test.txt", ios::in | ios::out | ios::trunc);

问题描述

fstream myFile("test.txt", ios::in | ios::out | ios::trunc);

编译器在C ++文件处理中如何解释这一行?

How is this line interpreted by the compiler in C++ file handling?

推荐答案

ios :: out 意味着您打算写入文件，而不是读取 ios :: in .在您的情况下，该流可以用于读取和写入.

ios::out means that you intend to write to the file in contrast to reading ios::in. In your case the stream can be used for both reading and writing.

ios :: trunc 表示将丢弃当前文件内容.将此与 ios :: app 进行比较，如果存在，您将在其中附加到文件.例如，如果未指定 ios :: in ，则暗示 ios :: trunc .当用于没有ios :: app的流时，ios :: ate或ios :: in，即表示ios :: trunc."

ios::trunc means that the current file content will be discarded. Compare this to ios::app where you will append to a file if it exists. ios::trunc is implied if not ios::in is specified for example. "When used for an ofstream without ios::app, ios::ate or ios::in, ios::trunc is implied."

奖金:

iso :: binary 意味着将要写的内容逐字放入文件中(否则，对于Windows \ n 可以用 \ n \代替r 例如)

iso::binary means that what you will write will be put verbatim into the file (otherwise for windows \n could be replaced with \n\r for example)

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