Defined in header <string> | ||
---|---|---|
template< class CharT, class Traits, class Allocator > std::basic_istream<CharT, Traits>& getline( std::basic_istream<CharT, Traits>& input, std::basic_string<CharT, Traits, Allocator>& str, CharT delim ); | (1) | |
template< class CharT, class Traits, class Allocator > std::basic_istream<CharT, Traits>& getline( std::basic_istream<CharT, Traits>&& input, std::basic_string<CharT, Traits, Allocator>& str, CharT delim ); | (2) | (since C++11) |
template< class CharT, class Traits, class Allocator > std::basic_istream<CharT, Traits>& getline( std::basic_istream<CharT, Traits>& input, std::basic_string<CharT, Traits, Allocator>& str ); | (3) | |
template< class CharT, class Traits, class Allocator > std::basic_istream<CharT, Traits>& getline( std::basic_istream<CharT, Traits>&& input, std::basic_string<CharT, Traits, Allocator>& str ); | (4) | (since C++11) |
getline
reads characters from an input stream and places them into a string:
input.gcount()
is not affected. After constructing and checking the sentry object, performs the following:str.erase()
input
and appends them to str
until one of the following occurs (checked in the order listed)delim
, as tested by Traits::eq(c, delim)
, in which case the delimiter character is extracted from input
, but is not appended to str
.getline
sets failbit
and returns.getline(input, str, input.widen('\n'))
, that is, the default delimiter is the endline character.input | - | the stream to get data from |
str | - | the string to put the data into |
delim | - | the delimiter character |
input
.
When consuming whitespace-delimited input (e.g. int n; std::cin >> n;
) any whitespace that follows, including a newline character, will be left on the input stream. Then when switching to line-oriented input, the first line retrieved with getline
will be just that whitespace. In the likely case that this is unwanted behaviour, possible solutions include:
getline
std::cin >> std::ws
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
The following example demonstrates how to use the getline
function to read user input, and to process a stream line by line, or by parts of a line using the delim
parameter.
#include <iostream> #include <sstream> #include <string> int main() { // greet the user std::string name; std::cout << "What is your name? "; std::getline(std::cin, name); std::cout << "Hello " << name << ", nice to meet you.\n"; // read file line by line std::istringstream input; input.str("1\n2\n3\n4\n5\n6\n7\n"); int sum = 0; for (std::string line; std::getline(input, line); ) sum += std::stoi(line); std::cout << "\nThe sum is " << sum << ".\n\n"; // use separator to read parts of the line std::istringstream input2; input2.str("a;b;c;d"); for (std::string line; std::getline(input2, line, ';'); ) std::cout << line << '\n'; }
Possible output:
What is your name? John Q. Public Hello John Q. Public, nice to meet you. The sum is 28. a b c d
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 91 | C++98 | getline did not behave as an unformatted input function | behaves as an unformatted input function |
extracts characters until the given character is found (public member function of std::basic_istream<CharT,Traits> ) |
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