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Programming-Idioms

  • Perl
  • Pascal

Idiom #278 Read one line from the standard input

Read one line into the string line.

Explain what happens if EOF is reached.

$line = <STDIN>;

The < > operator evaluates a filehandle, in this case the built-in filehandle STDIN, which in turn reads a line and returns it. $line contains its trailing newline, if it was present. If EOF is reached, the undefined value (undef) is returned. Perl treats undef as false when tested in a condition.
readln(line);

processing reading the inputs stops when EOF is reached.
with Ada.Text_IO;
Line : constant String := Ada.Text_IO.Get_Line;

End_Error is raised if EOF is reached.
New implementation...
< > ⌨
programming-idioms.org 
$line = <STDIN>;
readln(line);
Line : constant String := Ada.Text_IO.Get_Line;
int main() {
    for (std::string line; std::getline(std::cin, line);) {
        std::cout << line << std::endl;
    }
    return 0;
}
var line = Console.ReadLine();
s := bufio.NewScanner(os.Stdin)
if ok := s.Scan(); !ok {
	log.Fatal(s.Err())
}
line := s.Text()
String line = null;
Scanner in = new Scanner(System.in);
if(in.hasNextLine())
    line = in.nextLine();
Scanner s = new Scanner(System.in);
String line = s.nextLine();
s.close();
line = sys.stdin.readline()
line = gets
let mut buffer = String::new();
let mut stdin = io::stdin();
stdin.read_line(&mut buffer).unwrap();