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Showing content from https://en.cppreference.com/w/cpp/language/../named_req/../string/basic_string/getline.html below:

std::getline - cppreference.com

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

Behaves as

, except that

is not affected. After constructing and checking the sentry object, performs the following:

1) Calls str.erase().

2) Extracts characters from input and appends them to str until one of the following occurs (checked in the order listed)

end-of-file condition on

, in which case,

sets

.

b) the next available input character is delim, as tested by Traits::eq(c, delim), in which case the delimiter character is extracted from input, but is not appended to str.

characters have been stored, in which case

sets

and returns.

If no characters were extracted for whatever reason (not even the discarded delimiter),

sets

and returns.

3,4) Same as getline(input, str, input.widen('\n')), that is, the default delimiter is the endline 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:

• 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');.

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.

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