To open or re-open a file stream for input or output.
void open (const char* s, ios_base::openmode = ios_base::in | ios_base::out);
You would use the function open() to open a basic_fstream object and associate it with a file. You may use open() to reopen a file and associate it if the object was closed but not destroyed.
If an attempt is made to open a file in an inappropriate file opening mode, the file will not open and a test for the object will not give false, therefore use the function is_open() to check for file openings.
There is no return value.
| Opening Modes | stdio equivalent |
|---|---|
| Input Only | |
| ios:: in | "r" |
| ios:: binary | ios::in | "rb" |
| Output only | |
| ios::out | "w" |
| ios::binary | ios::out | "wb" |
| ios::out | ios::trunc | "w" |
| ios::binary | ios::out | ios::trunc | "wb" |
| ios::out | ios::app | "a" |
| Input and Output | |
| ios::in | ios::out | "r+" |
| ios::binary | ios::in | ios::out | "r+b" |
| ios:: in | ios::out | ios::trunc | "w+" |
| ios::binary | ios::in | ios::out | ios::trunc | "w+b" |
| ios::binary | ios:: out | ios::app | "ab" |
For an example, see Example of basic_fstream::rdbuf() usage.