C++ cin object

❮ iostream objects

int x; 
cout << "Type a number: "; // Type a number and press enter
cin >> x; // Get user input from the keyboard
cout << "Your number is: " << x; // Display the input value 

Definition and Usage

The cin object is used to read keyboard input or data from a file.

The most common way to use cin is with the >> extraction operator. The extraction operator converts input data to the appropriate type for the variable:

int x;
cin >> x;

The extraction operator can be used more than once on the same line to put data into multiple variables:

int x, y;
cin >> x >> y;

Note: The cin object is defined in the <iostream> header file.

Methods

In addition to the >> extraction operator, the cin object also has methods to read input.

get()

The cin.get() method reads one character from the input source and returns it.

char c = cin.get();
cout << c;

The cin.get(str, n) method writes up to n characters into the char array str which are copied from the input source. If a new line character \n is found it stops at the new line without including it. The last written character is always a null terminating character \0.

An extra parameter can be used to specify a different character than \n as a delimiter.

char str[20];
cin.get(str, 5);
cout << c;

// Stop reading when a "." is found
cin.get(str, 5, '.');
cout << c;

getline()

The cin.getline(str, n) method is the same as get(str, n) except that when the new line character \n or specified delimiter is found, it is discarded from the input source so that the next cin operation won't use it.

char str[20];
cin.getline(str, 5);
cout << c;

// Stop reading when a "." is found
cin.getline(str, 5, '.');
cout << c;

read()

The cin.read(str, n) method reads up to n characters from the input source and writes them into the char array str without checking for delimiters and without adding a null terminating character \0.

char str[] = "Hello World";
cin.read(str, 5);
cout << str;

gcount()

The cin.gcount() method returns the number of characters that were used from the input souce by one of the above methods.

char str[20];
cin.get(str, 5);
int num = cin.gcount();
cout << "Read " << num << " characters and got " << str << "\n";

cin.clear()

If cin enters a fail state (for example, if you enter text instead of a number), you must call cin.clear() to reset the error flag before taking more input.

cin.ignore()

The cin.ignore() method skips characters in the input buffer. It's commonly used after reading input to discard extra characters or the newline character left over by cin.

This is useful when switching between cin >> and getline() to avoid skipped input.

The parameters mean: skip up to 10000 characters or until a newline ('\n') is found, whichever comes first.

❮ iostream objects