Check that file exists

In this task, the job is to verify that a file called "input.txt" and the directory called "docs" exist. This should be done twice: once for the current working directory and once for a file and a directory in the filesystem root.

Ada

This example should work with any ada compiler. It has been tested with Gnat 3.15p

 with ada.text_io; use ada.text_io;
 procedure fileExists is  
    function file_exists( name : string ) return boolean is
       the_file:Ada.Text_IO.file_type;
    begin
       open(the_file, in_file, name);
       close( the_file);
       return true;
    exception
       when name_error =>
       return false;
    end file_exists;
    procedure putBool(bool: boolean) is
    begin
       if (bool) then
          put_line ("true");
       else
          put_line ("false");
       end if;  
    end;    
 begin  
    putBool( file_exists("input.txt" ) );
    putBool( file_exists("\input.txt") );    
 end;

C

#include <sys/types.h> 
#include <sys/stat.h>
#include <unistd.h>
int main(){
 struct stat file_stat;
 if(stat("/tmp/test",&file_stat) ==0)
   printf("file exists");
 else 
   printf("no file lol");
}

DOS Batch File

 if exist input.txt echo The following file called input.txt exists.
 if exist \input.txt echo The following file called \input.txt exists.
 if exist docs echo The following directory called docs exists.
 if exist \docs\ echo The following directory called \docs\ exists.

Forth

: .exists ( str len -- ) 2dup file-status nip 0= if type ."  exists" else type ."  does not exist" then ;
 s" input.txt" .exists
s" /input.txt" .exists
 s" docs" .exists
s" /docs" .exists

Java

import java.util.File;
public class FileExistsTest {
   public static boolean isFileExists(String filename) {
       boolean exists = new File(filename).exists();
       return exists;
   }
   public static void test(String type, String filename) {
       System.out.println("The following " + type + " called " + filename + 
           (isFileExists(filename) ? " exists." : " not exists.")
       );
   }
   public static void main(String args[]) {
        test("file", "input.txt");
        test("file", File.seperator + "input.txt");
        test("directory", "docs");
        test("directory", File.seperator + "docs" + File.seperator);
   }
}

Haskell

import System.IO
import System.Directory

check :: (FilePath -> IO Bool) -> FilePath -> IO ()
check p s = do
  result <- p s
  putStrLn $ s ++ if result then " does exist" else " does not exist"

main = do
  check doesFileExist "input.txt"
  check doesDirectoryExist "docs"
  check doesFileExist "/input.txt"
  check doesDirectoryExist "/docs"

MAXScript

-- Here
doesFileExist "input.txt"
(getDirectories "docs").count == 1
-- Root
doesFileExist "\input.txt"
(getDirectories "C:\docs").count == 1

OCaml

Sys.file_exists "input.txt";;
Sys.file_exists "docs";;
Sys.file_exists "/input.txt";;
Sys.file_exists "/docs";;

PHP

// List of files.
$files = array('./input.txt','./docs','/input.txt','/docs');
// Process Each File
foreach($files as $fileToCheck){
  // List Findings
  print "The file ";
  if( file_exists($fileToCheck) ){
    print $fileToCheck." exists.\n";
  }else{
    print $fileToCheck." does not exist.\n";
  }
}

Perl

use File::Spec::Functions qw(catfile rootdir);
# here
print -e 'input.txt';
print -d 'docs';
# root dir
print -e catfile rootdir, 'input.txt';
print -d catfile rootdir, 'docs';

Without a Perl Module

A 1 is printed if the file or dir exists.

perl -e 'print -e "./input.txt", "\n";'
perl -e 'print -d "./docs", "\n";'
perl -e 'print -e "/input.txt", "\n";'
perl -e 'print -d "/docs", "\n";'

Pop11

sys_file_exists('input.txt') =>
sys_file_exists('/input.txt') =>
sys_file_exists('docs') =>
sys_file_exists('/docs') =>

Note that the above literally checks for existence. Namely sys_file_exists returns true if file exists but can not be read.

The only sure method to check if file can be read is to try to open it. If one just wants to check if file is readable the following may be useful:

;;; Define an auxilary function, returns boolean
define file_readable(fname);
   lvars f = sysopen(fname, 0, true, `A`);
   if f then
       sysclose(f);
       return (true);
   else
       return (false);
   endif;
enddefine;

PowerShell

Test-Path input.txt

Python

Interpreter: Python 2.5

The os.path.exists method will return True if a path exists False if it does not.

 import os
 
 os.path.exists("input.txt")
 os.path.exists("/input.txt")
 os.path.exists("docs")
 os.path.exists("/docs")

Raven

'input.txt'  exists if 'input.txt exists'  print
'/input.txt' exists if '/input.txt exists' print
'docs'  isdir if 'docs exists and is a directory'  print
'/docs' isdir if '/docs exists and is a directory' print

Smalltalk

Squeak has no notion of 'current directory' because it isn't tied to the shell that created it.

  FileDirectory new fileExists: 'c:\serial'.
  (FileDirectory on: 'c:\') directoryExists: 'docs'.

In GNU Smalltalk instead you can do:

  (Directory name: 'docs') exists ifTrue: [ ... ]
  (Directory name: 'c:\docs') exists ifTrue: [ ... ]
  (File name: 'serial') isFile ifTrue: [ ... ]
  (File name: 'c:\serial') isFile ifTrue: [ ... ]

Using exists in the third and fourth case will return true for directories too.

Tcl

Taking the meaning of the task from the DOS example:

if { [file exists input.txt] } { puts "input.txt exists" } 
if { [file exists [file nativename /input.txt]] } { puts "/input.txt exists" }

if { [file isdirectory docs] } { puts "docs exists and is a directory" } 
if { [file isdirectory [file nativename /docs]] } { puts "/docs exists and is a directory" }

Toka

 [ "R" file.open dup 0 <> [ dup file.close ] ifTrue 0 <> ] is exists?
 " input.txt" exists? .
 " /input.txt" exists? .
 " docs" exists? .
 " /docs" exists? .

Visual Basic .NET

Platform: .NET

Language Version: 9.0+

'Current Directory
Console.WriteLine(If(IO.Directory.Exists("docs"), "directory exists", "directory doesn't exists"))
Console.WriteLine(If(IO.Directory.Exists("output.txt"), "file exists", "file doesn't exists"))

'Root
Console.WriteLine(If(IO.Directory.Exists("\docs"), "directory exists", "directory doesn't exists"))
Console.WriteLine(If(IO.Directory.Exists("\output.txt"), "file exists", "file doesn't exists"))

'Root, platform independent
Console.WriteLine(If(IO.Directory.Exists(IO.Path.DirectorySeparatorChar & "docs"), _ 
   "directory exists", "directory doesn't exists"))
Console.WriteLine(If(IO.Directory.Exists(IO.Path.DirectorySeparatorChar & "output.txt"), _ 
  "file exists", "file doesn't exists"))