std::getline
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 ); |
(1) | (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 ); |
(2) | |
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 ); |
(2) | (since C++11) |
getline
reads characters from an input stream and places them into a string:
1) Behaves as
UnformattedInputFunction, except that
input.gcount()
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)
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
.
3) If no characters were extracted for whatever reason (not even the discarded delimiter),
getline
sets
failbit
and returns.
2) Same as
getline(input, str, input.widen('\n'))
, that is, the default delimiter is the endline character.
Parameters
input | - | the stream to get data from |
str | - | the string to put the data into |
delim | - | the delimiter character |
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
The following example demonstrates how to use getline
function to read user's input and how to process file line by line.
#include <string> #include <iostream> #include <sstream> 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
See also
extracts characters until the given character is found (public member function of std::basic_istream<CharT,Traits> ) |
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