std::basic_istream::getline(3)

NAME
std::basic_istream::getline - std::basic_istream::getline

Synopsis
   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 no character is
                      case where count is non-positive extracted in this case

See also
   getline read data from an I/O stream into a string
              (function template)
   operator>> extracts formatted data
              (public member function)
   get extracts characters
              (public member function)
   read extracts blocks of characters
              (public member function)