NAME¶

std::basic_string_view::substr - std::basic_string_view::substr

Synopsis¶

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

Returns a view of the substring [pos, pos + rlen), where rlen 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 + rlen).

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, i.e. data[0, 5] that is [0, 6)
std::cout << data.substr(pos_t(1)) << '\n'; // BCDEF, i.e. [1, 6)
std::cout << data.substr(pos_t(2), count_t(3)) << '\n'; // CDE, i.e. [2, 2 + 3)
std::cout << data.substr(pos_t(4), count_t(42)) << '\n'; // EF, i.e. [4, 6)

try
{
[[maybe_unused]]
auto sub = 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 copies characters
(public member function)
find find characters in the view
(public member function)
substr returns a substring
(public member function of std::basic_string<CharT,Traits,Allocator>)