Difference between revisions of "cpp/string/basic string/getline"

Revision as of 22:28, 21 October 2023

getline reads characters from an input stream and places them into a string:

Parameters

Return value

input

Notes

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:

• An explicit extraneous initial call to getline.
• Removing consecutive whitespace with std::cin >> std::ws.
• Ignoring all leftover characters on the line of input with cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');.

Example

#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';
}

What is your name? John Q. Public
Hello John Q. Public, nice to meet you.
 
The sum is 28.
 
a
b
c
d

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also