std::basic_ofstream

< cpp‎ | io
 
C++
 
Input/output library
I/O manipulators
C-style I/O
Buffers
(deprecated in C++98)
(C++20)
Streams
Abstractions
File I/O
basic_ofstream
String I/O
Array I/O
(deprecated in C++98)
(deprecated in C++98)
(deprecated in C++98)
Synchronized Output
(C++20)
Types
Error category interface
(C++11)
(C++11)
 
std::basic_ofstream
 
Defined in header <fstream>
template<

    class CharT,
    class Traits = std::char_traits<CharT>

> class basic_ofstream : public std::basic_ostream<CharT, Traits>

The class template basic_ofstream implements high-level output operations on file based streams. It interfaces a file-based streambuffer (std::basic_filebuf) with the high-level interface of (std::basic_ostream).

A typical implementation of std::basic_ofstream holds only one non-derived data member: an instance of std::basic_filebuf<CharT, Traits>.

cpp/io/ios basecpp/io/basic ioscpp/io/basic ostreamstd-basic ofstream-inheritance.svg

Inheritance diagram

Two specializations for common character types are also defined:

Defined in header <fstream>
Type Definition
ofstream basic_ofstream<char>
wofstream basic_ofstream<wchar_t>

Member types

Member type Definition
char_type CharT
traits_type Traits; the program is ill-formed if Traits::char_type is not CharT.
int_type Traits::int_type
pos_type Traits::pos_type
off_type Traits::off_type

Member functions

 constructs the file stream
(public member function)
(destructor)
[virtual] (implicitly declared)
 destructs the basic_ofstream and the associated buffer, closes the file
(virtual public member function)
(C++11)
 moves the file stream
(public member function)
(C++11)
 swaps two file streams
(public member function)
returns the underlying raw file device object
(public member function)
File operations
checks if the stream has an associated file
(public member function)
opens a file and associates it with the stream
(public member function)
closes the associated file
(public member function)

Non-member functions

(C++11)
 specializes the std::swap algorithm
(function template)


Inherited from std::basic_ostream

Member functions

Formatted output
inserts formatted data
(public member function of std::basic_ostream<CharT,Traits>)
Unformatted output
inserts a character
(public member function of std::basic_ostream<CharT,Traits>)
inserts blocks of characters
(public member function of std::basic_ostream<CharT,Traits>)
Positioning
returns the output position indicator
(public member function of std::basic_ostream<CharT,Traits>)
sets the output position indicator
(public member function of std::basic_ostream<CharT,Traits>)
Miscellaneous
synchronizes with the underlying storage device
(public member function of std::basic_ostream<CharT,Traits>)

Member classes

 implements basic logic for preparation of the stream for output operations
(public member class of std::basic_ostream<CharT,Traits>)

Inherited from std::basic_ios

Member types

Member type Definition
char_type CharT
traits_type Traits
int_type Traits::int_type
pos_type Traits::pos_type
off_type Traits::off_type

Member functions

State functions
checks if no error has occurred i.e. I/O operations are available
(public member function of std::basic_ios<CharT,Traits>)
checks if end-of-file has been reached
(public member function of std::basic_ios<CharT,Traits>)
checks if an error has occurred
(public member function of std::basic_ios<CharT,Traits>)
checks if a non-recoverable error has occurred
(public member function of std::basic_ios<CharT,Traits>)
checks if an error has occurred (synonym of fail())
(public member function of std::basic_ios<CharT,Traits>)
(until C++11)(since C++11)
 checks if no error has occurred (synonym of !fail())
(public member function of std::basic_ios<CharT,Traits>)
returns state flags
(public member function of std::basic_ios<CharT,Traits>)
sets state flags
(public member function of std::basic_ios<CharT,Traits>)
modifies state flags
(public member function of std::basic_ios<CharT,Traits>)
Formatting
copies formatting information
(public member function of std::basic_ios<CharT,Traits>)
manages the fill character
(public member function of std::basic_ios<CharT,Traits>)
Miscellaneous
manages exception mask
(public member function of std::basic_ios<CharT,Traits>)
sets the locale
(public member function of std::basic_ios<CharT,Traits>)
manages associated stream buffer
(public member function of std::basic_ios<CharT,Traits>)
manages tied stream
(public member function of std::basic_ios<CharT,Traits>)
narrows characters
(public member function of std::basic_ios<CharT,Traits>)
widens characters
(public member function of std::basic_ios<CharT,Traits>)

Inherited from std::ios_base

Member functions

Formatting
manages format flags
(public member function of std::ios_base)
sets specific format flag
(public member function of std::ios_base)
clears specific format flag
(public member function of std::ios_base)
manages decimal precision of floating point operations
(public member function of std::ios_base)
manages field width
(public member function of std::ios_base)
Locales
sets locale
(public member function of std::ios_base)
returns current locale
(public member function of std::ios_base)
Internal extensible array
[static]
 returns a program-wide unique integer that is safe to use as index to pword() and iword()
(public static member function of std::ios_base)
resizes the private storage if necessary and access to the long element at the given index
(public member function of std::ios_base)
resizes the private storage if necessary and access to the void* element at the given index
(public member function of std::ios_base)
Miscellaneous
registers event callback function
(public member function of std::ios_base)
[static]
 sets whether C++ and C IO libraries are interoperable
(public static member function of std::ios_base)
Member classes
stream exception
(public member class of std::ios_base)
initializes standard stream objects
(public member class of std::ios_base)

Member types and constants

Type Explanation
stream open mode type

The following constants are also defined:

Constant Explanation
app seek to the end of stream before each write
binary open in binary mode
in open for reading
out open for writing
trunc discard the contents of the stream when opening
ate seek to the end of stream immediately after open

(typedef)
formatting flags type

The following constants are also defined:

Constant Explanation
dec use decimal base for integer I/O: see std::dec
oct use octal base for integer I/O: see std::oct
hex use hexadecimal base for integer I/O: see std::hex
basefield dec|oct|hex. Useful for masking operations
left left adjustment (adds fill characters to the right): see std::left
right right adjustment (adds fill characters to the left): see std::right
internal internal adjustment (adds fill characters to the internal designated point): see std::internal
adjustfield left|right|internal. Useful for masking operations
scientific generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific
fixed generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed
floatfield scientific|fixed. Useful for masking operations
boolalpha insert and extract bool type in alphanumeric format: see std::boolalpha
showbase generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase
showpoint generate a decimal-point character unconditionally for floating-point number output: see std::showpoint
showpos generate a + character for non-negative numeric output: see std::showpos
skipws skip leading whitespace before certain input operations: see std::skipws
unitbuf flush the output after each output operation: see std::unitbuf
uppercase replace certain lowercase letters with their uppercase
equivalents in certain output operations: see std::uppercase

(typedef)
state of the stream type

The following constants are also defined:

Constant Explanation
goodbit no error
badbit irrecoverable stream error
failbit input/output operation failed (formatting or extraction error)
eofbit associated input sequence has reached end-of-file

(typedef)
seeking direction type

The following constants are also defined:

Constant Explanation
beg the beginning of a stream
end the ending of a stream
cur the current position of stream position indicator

(typedef)
specifies event type
(enum)
callback function type
(typedef)

Example

Run this code
#include <iostream>
#include <fstream>
#include <string>
 
int main() {
    std::string filename = "Test.b";
    {
        std::ofstream ostrm(filename, std::ios::binary);
        double d = 3.14;
        ostrm.write(reinterpret_cast<char*>(&d), sizeof d); // binary output
        ostrm << 123 << "abc" << '\n';                      // text output
    }
    // read back
    std::ifstream istrm(filename, std::ios::binary);
    double d;
    istrm.read(reinterpret_cast<char*>(&d), sizeof d);
    int n;
    std::string s;
    istrm >> n >> s;
    std::cout << " read back: " << d << " " << n << " " << s << '\n';
}

Output: 

read back: 3.14 123 abc