std::basic_fstream::basic_fstream

(1) default constructor

Constructs a basic_fstream object that is not associated with any file.
Internally, its basic_iostream base constructor is passed a pointer to a newly constructed basic_filebuf object (the internal file stream buffer).

(2) initialization constructor

Constructs a basic_fstream object, initially associated with the file identified by its first argument (filename), open with the mode specified by mode.
Internally, its basic_iostream base constructor is passed a pointer to a newly constructed basic_filebuf object (the internal file stream buffer). Then, basic_filebuf::open is called with filename and mode as arguments.
If the file cannot be opened, the stream's failbit flag is set.

(3) copy constructor (deleted)

Deleted (no copy constructor).

(4) move constructor

Acquires the contents of x.
First, the function move-constructs both its base basic_iostream class from x and a basic_filebuf object from x's internal basic_filebuf object, and then associates them by calling member set_rdbuf.
x is left in an unspecified but valid state.

Parameters

filename

A string representing the name of the file to be opened.
Specifics about its format and validity depend on the library implementation and running environment.

mode

Flags describing the requested input/output mode for the file.
This is an object of the bitmask member type openmode that consists of a combination of the following member constants:

member constant	stands for	access
in	input	File open for reading: the internal stream buffer supports input operations.
out	output	File open for writing: the internal stream buffer supports output operations.
binary	binary	Operations are performed in binary mode rather than text.
ate	at end	The output position starts at the end of the file.
app	append	All output operations happen at the end of the file, appending to its existing contents.
trunc	truncate	Any contents that existed in the file before it is open are discarded.

These flags can be combined with the bitwise OR operator (|).

If the mode has both trunc and app set, the opening operation fails. It also fails if either is set but out is not, or if both app and in are set.

If the mode has both trunc and app set, the opening operation fails. It also fails if trunc is set but out is not.

x

A basic_fstream object of the same type (with the same class template parameters charT and traits), whose value is moved.

Example

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// fstream constructor.
#include <fstream>      // std::fstream
int main () {
  std::fstream fs ("test.txt", std::fstream::in | std::fstream::out);
  // i/o operations here
  fs.close();
  return 0;
}

Data races

Exception safety

See also

basic_fstream::open

Open file (public member function)