[C++] Input (ENG)

 

Input Stream

scanf has the input problem cause it doesn't do the boundary check, so does cin. For more security:

char name[4];
cin >> setw(4) >> name;

 

 

0	1	2	3
H	W	I	\0

 

 

Stream States

Old (C):

if (fgets(line, 10, stdin) != NULL)
{
    // ...
}

 

New:

cin >> line;
if (!cin.eof())
{
    // ...
}

 

Istream states

- namespace : ios_base

- bit flag : goodbit, eofbit, failbit, badbit

- method : good(), eof(), fail(), bad()

 

example

int number;
cin >> number;

 

input	eofbit	failbit
456abc	unset	unset
456	console - unset / file - set	unset
abc	unset	set
eof	set	set

 

 

Discarding Input

clear( )

makes good state

cin.clear();

 

ignore( )

stops when reaches the eof or discards the specified number of characters

cin.ignore(); // discard 1 character
cin.ignore(10); // discard 10 characters
cin.ignore(10, '\n'); // discard 10 characters, stop when discard the newline char
cin.ignore(LLONG_MAX, '\n'); // discard LLONG_MAX, stop when discard the newline char

 

get( )

retrieves all characters before the newline character. Newline character remains in the input stream.

get(name, 100);
// get 99 chars or chars before the newline char
// put the chars in the array 'name'

get(name, 100, '#');
// get 99 chars or chars before the '#' char
// put the chars in the array 'name'

 

getline( )

retrieves all characters before the newline character. Newline character is discarded in the input stream.

getline(name, 100);
getline(name, 100, '#');