Check input device is a terminal

From Rosetta Code
Task
Check input device is a terminal
You are encouraged to solve this task according to the task description, using any language you may know.
Task

Demonstrate how to check whether the input device is a terminal or not.


Related task



Ada[edit]

Works with: GNAT

We use the interface to C library functions isatty() and fileno().

with Ada.Text_IO;          use Ada.Text_IO;
with Interfaces.C_Streams; use Interfaces.C_Streams;

procedure Test_tty is
begin
   if Isatty(Fileno(Stdin)) = 0 then
      Put_Line(Standard_Error, "stdin is not a tty.");
   else
      Put_Line(Standard_Error, "stdin is a tty.");
   end if;
end Test_tty;
Output:
$ ./test_tty 
stdin is a tty.
$ ./test_tty < /dev/null
stdin is not a tty.

BaCon[edit]

terminal = isatty(0)
PRINT terminal
Output:
prompt$ bacon -q istty.bac
Converting 'istty.bac'... done, 4 lines were processed in 0.002 seconds.
Compiling 'istty.bac'... cc  -c istty.bac.c
cc -o istty istty.bac.o    -lm
Done, program 'istty' ready.
prompt$ ./istty
1
prompt$ ./istty <<<"testing"
0

C[edit]

Use isatty() on file descriptor to determine if it's a TTY. To get the file descriptor from a FILE* pointer, use fileno:

#include <unistd.h>	//for isatty()
#include <stdio.h>	//for fileno()

int main(void)
{
	puts(isatty(fileno(stdin))
		? "stdin is tty"
		: "stdin is not tty");
	return 0;
}
Output:
$ ./a.out
stdin is tty
$ ./a.out < /dev/zero
stdin is not tty
$ echo "" | ./a.out
stdin is not tty

COBOL[edit]

Works with GnuCOBOL.

      *>
      *> istty, check id fd 0 is a tty
      *> Tectonics: cobc -xj istty.cob
      *>            echo "test" | ./istty
      *>
       identification division.
       program-id. istty.

       data division.
       working-storage section.
       01 rc usage binary-long.

       procedure division.
       sample-main.

       call "isatty" using by value 0 returning rc
       display "fd 0 tty: " rc

       call "isatty" using by value 1 returning rc
       display "fd 1 tty: " rc upon syserr

       call "isatty" using by value 2 returning rc
       display "fd 2 tty: " rc

       goback.
       end program istty.

DISPLAY for fd 1 is directed to SYSERR to get some output during the various trials.

Output:
prompt$ cobc -xj istty.cob
fd 0 tty: +0000000001
fd 1 tty: +0000000001
fd 2 tty: +0000000001
prompt$ echo "test" | ./istty
fd 0 tty: +0000000000
fd 1 tty: +0000000001
fd 2 tty: +0000000001
prompt$ echo "test" | ./istty >/dev/null
fd 1 tty: +0000000000
prompt$ echo "test" | ./istty 2>/dev/tty
fd 0 tty: +0000000000
fd 1 tty: +0000000001
fd 2 tty: +0000000001
prompt$ echo "test" | ./istty 2>/dev/null
fd 0 tty: +0000000000
fd 2 tty: +0000000000

Common Lisp[edit]

Works with: SBCL
(with-open-stream (s *standard-input*)
  (format T "stdin is~:[ not~;~] a terminal~%" 
          (interactive-stream-p s)))
Output:
$ sbcl --script rc.lisp
stdin is a terminal
$ sbcl --script rc.lisp < /dev/zero
stdin is not a terminal
$ echo "" | sbcl --script rc.lisp
stdin is not a terminal

Crystal[edit]

File.new("testfile").tty?   #=> false
File.new("/dev/tty").tty?   #=> true
STDIN.tty?  #=> true

D[edit]

import std.stdio;

extern(C) int isatty(int);

void main() {
    if (isatty(0))
        writeln("Input comes from tty.");
    else
        writeln("Input doesn't come from tty.");
}
Output:
C:\test
Input comes from tty.
C:\test < in.txt
Input doesn't come from tty.

FreeBASIC[edit]

Open Cons For Input As #1
' Open Cons abre los flujos de entrada (stdin) o salida (stdout) estándar 
' de la consola para leer o escribir. 

If Err Then
    Print "Input doesn't come from tt."
Else
    Print "Input comes from tty."
End If  
Close #1
Sleep


FutureBasic[edit]

include "NSLog.incl"

BeginCCode
  if (isatty(fileno(stdin)))
  NSLog( @"stdin is connected to a terminal" );
  else
  NSLog( @"stdin is NOT connected to a terminal" );
EndC

HandleEvents
Output:
stdin is NOT connected to a terminal


Go[edit]

package main

import (
    "golang.org/x/crypto/ssh/terminal"
    "fmt"
    "os"
)

func main() {
    if terminal.IsTerminal(int(os.Stdin.Fd())) {
        fmt.Println("Hello terminal")
    } else {
        fmt.Println("Who are you?  You're not a terminal.")
    }
}
Output:
> hello
Hello terminal
> hello </dev/null
Who are you?  You're not a terminal.


Haskell[edit]

Example uses unix package:

module Main (main) where
 
import           System.Posix.IO (stdInput)
import           System.Posix.Terminal (queryTerminal)
 
main :: IO ()
main = do
    isTTY <- queryTerminal stdInput
    putStrLn $ if isTTY
                then "stdin is TTY"
                else "stdin is not TTY"

Jsish[edit]

/* Check input device is a terminal, in Jsish */
;Interp.conf().subOpts.istty;

/*
=!EXPECTSTART!=
Interp.conf().subOpts.istty ==> false
=!EXPECTEND!=
*/
Output:
prompt$ jsish
Jsish interactive: see 'help [cmd]' or 'history'.  \ cancels > input.  ctrl-c aborts running script.
jsi> Interp.conf().subOpts.istty;
true
jsi>
prompt$ jsish --U checkInputDevice.jsi
Interp.conf().subOpts.istty ==> false

Julia[edit]

if isa(STDIN, Base.TTY)
    println("This program sees STDIN as a TTY.")
else
    println("This program does not see STDIN as a TTY.")
end
Output:
This program sees STDIN as a TTY.

Kotlin[edit]

Works with: Ubuntu version 14.04
// Kotlin Native version 0.5

import platform.posix.*

fun main(args: Array<String>) {
    if (isatty(STDIN_FILENO) != 0)
        println("stdin is a terminal")
    else
        println("stdin is not a terminal") 
}
Output:
stdin is a terminal

Nemerle[edit]

There is no explicit way (ie isatty())to do this; however, if we assume that standard input is a terminal, we can check if the input stream has been redirected (presumably to something other than a terminal).

def isTerm = System.Console.IsInputRedirected;

Nim[edit]

Using function "isatty" of standard module "terminal" which accepts a File as argument.

import terminal

echo if stdin.isatty: "stdin is a terminal" else: "stdin is not a terminal"
Output:
Command: ./check_input_dev
Result: stdin is a terminal
Command: ./check_input_dev <somefile
Result: stdin is not a terminal

OCaml[edit]

let () =
  print_endline (
    if Unix.isatty Unix.stdin
    then "Input comes from tty."
    else "Input doesn't come from tty."
  )

Testing in interpreted mode:

$ ocaml unix.cma istty.ml
Input comes from tty.
$ echo "foo" | ocaml unix.cma istty.ml
Input doesn't come from tty.

Ol[edit]

(define (isatty? fd) (syscall 16 fd 19))
(print (if (isatty? stdin)
   "Input comes from tty."
   "Input doesn't come from tty."))

Perl[edit]

use strict;
use warnings;
use 5.010;
if (-t) {
    say "Input comes from tty.";
}
else {
    say "Input doesn't come from tty.";
}
$ perl istty.pl
Input comes from tty.
$ true | perl istty.pl
Input doesn't come from tty.

Phix[edit]

without js -- (no input redirection in a browser!)
printf(1,"stdin:%t, stdout:%t, stderr:%t\n",{isatty(0),isatty(1),isatty(2)})
Output:
C:\Program Files (x86)\Phix>p test
stdin:true, stdout:true, stderr:true
C:\Program Files (x86)\Phix>echo hello | p test
stdin:false, stdout:true, stderr:true

Pike[edit]

void main()
{
    if(Stdio.Terminfo.is_tty())
	write("Input comes from tty.\n");
    else
        write("Input doesn't come from tty.\n");
}
Output:
$ ./istty.pike
Input comes from tty.
$ echo | ./istty.pike
Input doesn't come from tty.

Python[edit]

from sys import stdin
if stdin.isatty():
    print("Input comes from tty.")
else:
    print("Input doesn't come from tty.")
$ python istty.py
Input comes from tty.
$ true | python istty.py
Input doesn't come from tty.

Quackery[edit]

Translation of: Python
  [ $ |from sys import stdin
to_stack( 1 if stdin.isatty() else 0)|
    python ]                            is ttyin ( --> b )     

  ttyin if 
    [ say "Looks like a teletype." ] 
  else 
    [ say "Not a teletype." ]
Output:
Looks like a teletype.

Racket[edit]

(terminal-port? (current-input-port))

Raku[edit]

(formerly Perl 6)

Works with: Rakudo version 2015.12
say $*IN.t ?? "Input comes from tty." !! "Input doesn't come from tty.";
$ raku istty.raku
Input comes from tty.
$ true | raku istty.raku
Input doesn't come from tty.

REXX[edit]

/*REXX program determines if input comes from terminal or standard input*/

if queued()  then say 'input comes from the terminal.'
             else say 'input comes from the (stacked) terminal queue.'

                                       /*stick a fork in it, we're done.*/

Ring[edit]

# Project  : Check input device is a terminal
 
load "stdlib.ring"

if isWindows()
   write("mycmd.bat","
   @echo off
    timeout 1 2>nul >nul
    if errorlevel 1 (
       echo input redirected
        ) else (
       echo input is console
       )
       ")
    see SystemCmd("mycmd.bat")
ok

Output:

input redirected

Ruby[edit]

Example from the docs.

File.new("testfile").isatty   #=> false
File.new("/dev/tty").isatty   #=> true

Rust[edit]

/* Uses C library interface */

extern crate libc;

fn main() {
    let istty = unsafe { libc::isatty(libc::STDIN_FILENO as i32) } != 0;
    if istty {
        println!("stdout is tty");
    } else {
        println!("stdout is not tty");
    }
}

Scala[edit]

Works with: Ubuntu version 14.04
import org.fusesource.jansi.internal.CLibrary._

object IsATty  extends App {

  var enabled = true

  def apply(enabled: Boolean): Boolean = {
    // We must be on some unix variant..
    try {
      enabled && isatty(STDIN_FILENO) == 1
    }
    catch {
      case ignore: Throwable =>
        ignore.printStackTrace()
        false

    }
  }

    println("tty " + apply(true))
}

Standard ML[edit]

val stdinRefersToTerminal : bool = Posix.ProcEnv.isatty Posix.FileSys.stdin

Tcl[edit]

Tcl automatically detects whether stdin is coming from a terminal (or a socket) and sets up the channel to have the correct type. One of the configuration options of a terminal channel is -mode (used to configure baud rates on a real serial terminal) so we simply detect whether the option is present.

if {[catch {fconfigure stdin -mode}]} {
    puts "Input doesn't come from tty."
} else {
    puts "Input comes from tty."
}

Demonstrating:

$ tclsh8.5 istty.tcl 
Input comes from tty.
$ tclsh8.5 istty.tcl </dev/null
Input doesn't come from tty.

UNIX Shell[edit]

#!/bin/sh

if [ -t 0 ]
then
   echo "Input is a terminal"
else
   echo "Input is NOT a terminal"
fi

Wren[edit]

import "io" for Stdin

System.print("Input device is a terminal? %(Stdin.isTerminal ? "Yes" : "No")")
Output:
Input device is a terminal? Yes

zkl[edit]

On Unix, check to see if stdin's st_mode is a character device.

const S_IFCHR=0x2000;
fcn S_ISCHR(f){ f.info()[4].bitAnd(S_IFCHR).toBool() }
S_ISCHR(File.stdin).println();
Output:
$ zkl bbb  # from the command line
True
$ zkl bbb < bbb.zkl
False
$ cat bbb.zkl | zkl bbb
False