std::basic_string_view<CharT,Traits>::substr

 

C++

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Feature test macros (C++20)

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Technical specifications

Symbols index

External libraries

 

Strings library

Null-terminated strings

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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)

 

constexpr basic_string_view substr( size_type pos = 0,                                     size_type count = npos ) const;		(since C++17)

Returns a view of the substring [pos, pos + rcount), where rcount is the smaller of count and size() - pos.

Parameters

pos	-	position of the first character
count	-	requested length

Return value

View of the substring [pos, pos + rcount).

Exceptions

std::out_of_range if pos > size()

Complexity

Constant.

Example

Run this code

#include <cstddef>
#include <iostream>
#include <stdexcept>
#include <string_view>
 
int main()
{
    typedef std::size_t count_t, pos_t;
 
    constexpr std::string_view data{"ABCDEF"};
 
    std::cout << data.substr() << '\n'; // ABCDEF
    std::cout << data.substr(pos_t(1)) << '\n'; // BCDEF
    std::cout << data.substr(pos_t(2), count_t(3)) << '\n'; // CDE
 
    std::cout << data.substr(pos_t(4), count_t(42)) << '\n'; // EF
        // count -> 2 == size() - pos == 6 - 4
 
    try {
        data.substr(pos_t(666), count_t(1)); // throws: pos > size()
    }
    catch(std::out_of_range const& ex) {
        std::cout << ex.what() << '\n';
    }
}

Possible output:

ABCDEF
BCDEF
CDE
EF
basic_string_view::substr: __pos (which is 666) > __size (which is 6)

See also

copy (C++17)	copies characters (public member function)
find (C++17)	find characters in the view (public member function)
substr	returns a substring (public member function of std::basic_string<CharT,Traits,Allocator>)