operator<<(std::basic_string_view)

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string_view

Member functions basic_string_view::basic_string_view    basic_string_view::operator= Iterators basic_string_view::beginbasic_string_view::cbegin basic_string_view::endbasic_string_view::cend basic_string_view::rbeginbasic_string_view::crbegin basic_string_view::rendbasic_string_view::crend Element access basic_string_view::at basic_string_view::operator[] basic_string_view::front basic_string_view::back basic_string_view::data Capacity basic_string_view::sizebasic_string_view::length basic_string_view::max_size basic_string_view::empty Modifiers basic_string_view::remove_prefix basic_string_view::remove_suffix basic_string_view::swap

Operations basic_string_view::copy basic_string_view::substr basic_string_view::compare basic_string_view::starts_with (C++20) basic_string_view::ends_with (C++20) basic_string_view::contains (C++23) basic_string_view::find basic_string_view::rfind basic_string_view::find_first_of basic_string_view::find_last_of basic_string_view::find_first_not_of basic_string_view::find_last_not_of Constants basic_string_view::npos Non-member functions operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) operator<< operator""sv Helper classes hash<std::string_view>hash<std::wstring_view>hash<std::u8string_view>hash<std::u16string_view>hash<std::u32string_view> (C++20) Deduction guides(C++20)

 

Defined in header <string_view>
template< class CharT, class Traits > std::basic_ostream<CharT, Traits>&     operator<<( std::basic_ostream<CharT, Traits>& os,                 std::basic_string_view <CharT, Traits> v );		(since C++17)

Behaves as a FormattedOutputFunction. After constructing and checking the sentry object, determines the output format padding as follows:

a) If v.size() is not less than os.width(), uses the range [v.begin(), v.end()) as-is

b) Otherwise, if (os.flags() & ios_base::adjustfield) == ios_base::left, places os.width()-v.size() copies of the os.fill() character after the character sequence

c) Otherwise, places os.width()-v.size() copies of the os.fill() character before the character sequence

Then stores each character from the resulting sequence (the contents of v plus padding) to the output stream os as if by calling os.rdbuf()->sputn(seq, n), where n=std::max(os.width(), str.size())

Finally, calls os.width(0) to cancel the effects of std::setw, if any.

Exceptions

May throw std::ios_base::failure if an exception is thrown during output.

Parameters

os	-	a character output stream
v	-	the view to be inserted

Return value

os

Example

Run this code

#include <iomanip>
#include <iostream>
#include <string_view>
 
int main() {
    constexpr std::string_view s{"abc"};
    constexpr int width{5};
    constexpr char fill{'-'};
 
    std::cout
       << std::setfill(fill)
       << "[" << s << "]\n"
       << "[" << std::left << std::setw(width) << s << "]\n"
       << "[" << std::right << std::setw(width) << s << "]\n";
}

Output:

[abc]
[abc--]
[--abc]

See also

operator<<operator>>

performs stream input and output on strings (function template)