std::basic_istream<CharT,Traits>::getline

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std::basic_istream
 
basic_istream& getline( char_type* s, std::streamsize count );
 (1)
basic_istream& getline( char_type* s, std::streamsize count, char_type delim );
 (2)

Extracts characters from stream until end of line or the specified delimiter delim.

The first overload is equivalent to getline(s, count, widen('\n')).

Behaves as UnformattedInputFunction. After constructing and checking the sentry object, extracts characters from *this and stores them in successive locations of the array whose first element is pointed to by s, until any of the following occurs (tested in the order shown):

  1. end of file condition occurs in the input sequence.
  2. the next available character c is the delimiter, as determined by Traits::eq(c, delim). The delimiter is extracted (unlike basic_istream::get()) and counted towards gcount(), but is not stored.
  3. count is non-positive, or count - 1 characters have been extracted (setstate(failbit) is called in this case).

If the function extracts no characters, ​failbit is set in the local error state before setstate() is called.

In any case, if count > 0, it then stores a null character CharT() into the next successive location of the array and updates gcount().

Notes

Because condition #2 is tested before condition #3, the input line that exactly fits the buffer does not trigger failbit.

Because the terminating character is counted as an extracted character, an empty input line does not trigger failbit.

Parameters

s - pointer to the character string to store the characters to
count - size of character string pointed to by s
delim - delimiting character to stop the extraction at. It is extracted but not stored.

Return value

*this

Exceptions

failure if an error occurred (the error state flag is not goodbit) and exceptions() is set to throw for that state.

If an internal operation throws an exception, it is caught and badbit is set. If exceptions() is set for badbit, the exception is rethrown.

Example

Run this code
#include <array>
#include <iostream>
#include <sstream>
#include <vector>
 
int main()
{
    std::istringstream input("abc|def|gh");
    std::vector<std::array<char, 4>> v;
 
    // note: the following loop terminates when std::ios_base::operator bool()
    // on the stream returned from getline() returns false
    for (std::array<char, 4> a; input.getline(&a[0], 4, '|');)
        v.push_back(a);
 
    for (auto& a : v)
        std::cout << &a[0] << '\n';
}

Output: 

abc
def
gh

Defect reports

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

DR Applied to Behavior as published Correct behavior
LWG 531 C++98 std::getline could not handle the
case where count is non-positive 		no character is
extracted in this case

See also

 read data from an I/O stream into a string
(function template)
extracts formatted data
(public member function)
extracts characters
(public member function)
extracts blocks of characters
(public member function)
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