std::basic_filebuf::open
性病：基本[医]文件：：打开
| std::basic_filebuf | (1) | |
|---|---|---|
| std::basic_filebuf<CharT, Traits>* open( const std::string& str, std::ios_base::openmode mode ) | (2) | (since C++11) |
| std::basic_filebuf<CharT, Traits>* open( const std::filesystem::path& p, std::ios_base::openmode mode ) | (3) | (since C++17) |
| std::basic_filebuf<CharT, Traits>* open( const std::filesystem::path::value_type* s, std::ios_base::openmode mode ) | (4) | (since C++17) |
以给定的名称%28打开文件s，，，p.c_str()%28自C++17%29或str.c_str()，取决于过载%29。
| Overload (4) is only provided if std::filesystem::path::value_type is not char. | (since C++17) |
|---|
打开该文件时，就好像通过调用std::fopen(s, modestring)，在哪里modestring决定如下：
| modestring | openmode & ~ate | Action if file already exists | Action if file does not exist |
|---|---|---|---|
| "r" | in | Read from start | Failure to open |
| "w" | out, out|trunc | Destroy contents | Create new |
| "a" | app, out|app | Append to file | Create new |
| "r+" | out|in | Read from start | Error |
| "w+" | out|in|trunc | Destroy contents | Create new |
| "a+" | out|in|app, in|app | Write to end | Create new |
| "rb" | binary|in | Read from start | Failure to open |
| "wb" | binary|out, binary|out|trunc | Destroy contents | Create new |
| "ab" | binary|app, binary|out|app | Write to end | Create new |
| "r+b" | binary|out|in | Read from start | Error |
| "w+b" | binary|out|in|trunc | Destroy contents | Create new |
| "a+b" | binary|out|in|app, binary|in|app | Write to end | Create new |
如果openmode不是列出的模式之一，open()失败了。
如果打开的操作成功，并且openmode &std::ios_base::ate!=0%28ate位设置为%29，将文件位置重新定位到文件末尾，就像通过调用std::fseek(file, 0,SEEK_END)如果重新定位失败，调用close()并返回指示失败的空指针。
如果关联文件已经打开，则立即返回一个空指针。
参数
| s, str, p | - | the file name to open |
|---|---|---|
| openmode | - | the file opening mode, a binary OR of the std::ios_base modes |
返回值
this如果成功，则为失败的空指针。
注记
open()通常通过构造函数或open()成员函数std::basic_fstream...
例
另见
| is_open | checks if the associated file is open (public member function) |
|---|---|
| close | flushes the put area buffer and closes the associated file (public member function) |
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