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Programming-Idioms

  • Fortran
  • Rust
  • JS
  • Elixir

Idiom #120 Read integer from stdin

Read an integer value from the standard input into the variable n

n = String.to_integer IO.gets ""
   integer :: n
   read (*,*) n
use std::io::BufRead;
let n: i32 = std::io::stdin()
    .lock()
    .lines()
    .next()
    .expect("stdin should be available")
    .expect("couldn't read from stdin")
    .trim()
    .parse()
    .expect("input was not an integer");
#[macro_use] extern crate text_io;
let n: i32 = read!();

Can also parse several values and types and delimiters with scan!()

Also see Rust RFC #3183
fn get_input() -> String {
    let mut buffer = String::new();
    std::io::stdin().read_line(&mut buffer).expect("Failed");
    buffer
}

let n = get_input().trim().parse::<i64>().unwrap();

Change i64 to what you expect to get. Do not use unwrap() if you're not sure it will be parsed correctly.
use std::io;
let mut input = String::new();
io::stdin().read_line(&mut input).unwrap();
let n: i32 = input.trim().parse().unwrap();
const {createInterface} = require('readline')

const rl = createInterface ({
  input: process.stdin,
  output: process.stdout
})

rl.question('Input an integer: ', response => {
  let n = parseInt (response)
  // stuff to be done with n goes here

  rl.close()
})

This example only works with nodeJS (server-side JS) because browser JS does not have a standard input.
#include <stdio.h>
int n[15];
fgets(n, 15, stdin);

int n[15]; Int with 15 bytes to use.

Fgets gets user input, and sets n to what it gets
New implementation...
< > ⌨
programming-idioms.org 
n = String.to_integer IO.gets ""
   integer :: n
   read (*,*) n
let n: i32 = std::io::stdin()
    .lock()
    .lines()
    .next()
    .expect("stdin should be available")
    .expect("couldn't read from stdin")
    .trim()
    .parse()
    .expect("input was not an integer");
let n: i32 = read!();

fn get_input() -> String {
    let mut buffer = String::new();
    std::io::stdin().read_line(&mut buffer).expect("Failed");
    buffer
}

let n = get_input().trim().parse::<i64>().unwrap();
let mut input = String::new();
io::stdin().read_line(&mut input).unwrap();
let n: i32 = input.trim().parse().unwrap();
const {createInterface} = require('readline')

const rl = createInterface ({
  input: process.stdin,
  output: process.stdout
})

rl.question('Input an integer: ', response => {
  let n = parseInt (response)
  // stuff to be done with n goes here

  rl.close()
})
int n[15];
fgets(n, 15, stdin);
int n;
scanf("%d", &n);
(def n (Integer/parseInt (read-line)))
IDENTIFICATION DIVISION.
PROGRAM-ID. stdin.
PROCEDURE DIVISION.
    ACCEPT n
STOP RUN.
std::cin >> n;
n = int.Parse(Console.ReadLine());
readf("%d", &n);
String? s = stdin.readLineSync();  
int? n = int.tryParse(s ?? "");
_, err := fmt.Scanf("%d", &n)
_, err := fmt.Scan(&n)
n <- (read :: String -> Int) <$> getContents
Scanner in = new Scanner(System.in);
n = in.nextInt();
Scanner s = new Scanner(System.in);
int n = parseInt(s.nextLine());
s.close();
Scanner in = new Scanner(System.in);
int n = in.nextInt();
(setf n (read-from-string (remove-if-not #'digit-char-p (read-line))))
n = io.read("n")
scanf("%d",&n);
fscanf(STDIN, "%d\n", $n);
read(n);
my $n = <> + 0;  # read a line from STDIN, add 0 to convert to int
n = int(input("Input Prompting String: "))
n = int(input())
n = $stdin.gets.to_i
val n = Try(StdIn.readInt())