Check that file exists

Check that file exists
You are encouraged to solve this task according to the task description, using any language you may know.

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 95 compiler. <lang ada>with Ada.Text_IO; use Ada.Text_IO;

procedure File_Exists is

  function Does_File_Exist (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 Does_File_Exist;

begin

  Put_Line (Boolean'Image (Does_File_Exist ("input.txt" )));
  Put_Line (Boolean'Image (Does_File_Exist ("\input.txt")));

end File_Exists;</lang> This example should work with any Ada 2005 compiler. <lang ada>with Ada.Text_IO; use Ada.Text_IO; with Ada.Directories; use Ada.Directories;

procedure File_Exists is

  procedure Print_File_Exist (Name : String) is
  begin
     Put_Line ("Does " & Name & " exist? " &
                 Boolean'Image (Exists (Name)));
  end Print_File_Exist;
  procedure Print_Dir_Exist (Name : String) is
  begin
     Put_Line ("Does directory " & Name & " exist? " &
                 Boolean'Image (Exists (Name) and then Kind (Name) = Directory));
  end Print_Dir_Exist;

begin

  Print_File_Exist ("input.txt" );
  Print_File_Exist ("/input.txt");
  Print_Dir_Exist ("docs");
  Print_Dir_Exist ("/docs");

end File_Exists;</lang>

AutoHotkey

AutoHotkey’s FileExist() function returns an attribute string (a subset of "RASHNDOCT") if a matching file or directory is found. The attribute string must be parsed for the letter D to determine whether the match is a directory or file. <lang autohotkey>ShowFileExist("input.txt") ShowFileExist("\input.txt") ShowFolderExist("docs") ShowFolderExist("\docs") return

ShowFileExist(file) {

  if ( FileExist(file)  && !InStr(FileExist(file), "D"))
     MsgBox, file: %file% exists.
  else
     MsgBox, file: %file% does NOT exist.
  return

}

ShowFolderExist(folder) {

  if InStr(FileExist(folder), "D")
        MsgBox, folder: %folder% exists.
  else
     MsgBox, folder: %folder% does NOT exist.
  return

}</lang>

C

Works with: POSIX

<lang c>#include <sys/types.h>

1. include <sys/stat.h>
2. include <unistd.h>

int main(){

 struct stat file_stat;
 if(stat("/tmp/test",&file_stat) ==0)
   printf("file exists");
 else 
   printf("no file lol");
 return 0;

}</lang>

C#

<lang csharp>using System.IO;

Console.WriteLine(File.Exists("input.txt")); Console.WriteLine(File.Exists("/input.txt")); Console.WriteLine(Directory.Exists("docs")); Console.WriteLine(Directory.Exists("/docs"));</lang>

Clojure

 (import '(java.io File))
 (doseq file (list (new File "input.txt")
                   (new File "/input.txt"))
   (when (not (. file exists)) (println file "is missing"))
   (when (. file isDirectory)  (println file "is a directory!")))
 
 (doseq file (list (new File "docs")
                   (new File "/docs"))
   (when (not (. file exists)) (println file "is missing"))
   (when (. file isDirectory)  (println file "is a directory!"))

Common Lisp

probe-file returns nil if a file does not exist. directory returns nil if there are no files in a specified directory. <lang lisp>(if (probe-file (make-pathname :name "input.txt"))

   (print "rel file exists"))

(if (probe-file (make-pathname :directory '(:absolute "") :name "input.txt"))

   (print "abs file exists"))

(if (directory (make-pathname :directory '(:relative "docs")))

   (print "rel directory exists")
   (print "rel directory is not known to exist"))

(if (directory (make-pathname :directory '(:absolute "docs")))

   (print "abs directory exists")
   (print "abs directory is not known to exist"))</lang>

There is no standardized way to determine if an empty directory exists, as Common Lisp dates from before the notion of directories as a type of file was near-universal. CL-FAD provides many of the therefore-missing capabilities in a cross-implementation library.

Library: CL-FAD

<lang lisp>(if (cl-fad:directory-exists-p (make-pathname :directory '(:relative "docs")))

   (print "rel directory exists")
   (print "rel directory does not exist"))</lang>

D

<lang d> import std.file, std.path: sep;

void verify(string name) {

 if (name.exists()) writefln(name, " exists");
 else writefln(name, " doesn't exist");

}

void main() {

 // check in current working dir
 verify("input.txt"); verify("docs");
 // check in root
 verify(sep~"input.txt"); verify(sep~"docs");

} </lang>

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.

E

for file in [<file:input.txt>,
             <file:///input.txt>] {
  require(file.exists(),       fn { `$file is missing!` })
  require(!file.isDirectory(), fn { `$file is a directory!` })
}

for file in [<file:docs>,
             <file:///docs>] {
  require(file.exists(),      fn { `$file is missing!` })
  require(file.isDirectory(), fn { `$file is not a directory!` })
}

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

Fortran

Works with: Fortran version 90 and later

Cannot check for directories in Fortran

LOGICAL :: file_exists
INQUIRE(FILE="input.txt", EXIST=file_exists)   ! file_exists will be TRUE if the file exists and FALSE otherwise
INQUIRE(FILE="/input.txt", EXIST=file_exists)   

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"

Java

<lang java>import java.io.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.separator + "input.txt");
       test("directory", "docs");
       test("directory", File.separator + "docs" + File.separator);
  }

}</lang>

MAXScript

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

Objective-C

<lang objc>NSFileManager *fm = [NSFileManager defaultManager]; NSLog(@"input.txt %s", [fm fileExistsAtPath:@"input.txt"] ? @"exists" : @"doesn't exist"); NSLog(@"docs %s", [fm fileExistsAtPath:@"docs"] ? @"exists" : @"doesn't exist");</lang>

OCaml

<lang ocaml>Sys.file_exists "input.txt";; Sys.file_exists "docs";; Sys.file_exists "/input.txt";; Sys.file_exists "/docs";;</lang>

PHP

<lang php>if (file_exists('input.txt')) echo 'input.txt is here right by my side'; if (file_exists('docs' )) echo 'docs is here with me'; if (file_exists('/input.txt')) echo 'input.txt is over there in the root dir'; if (file_exists('/docs' )) echo 'docs is over ther in the root dir';</lang>

Perl

<lang perl>use File::Spec::Functions qw(catfile rootdir);

1. here

print -e 'input.txt'; print -d 'docs';

1. root dir

print -e catfile rootdir, 'input.txt'; print -d catfile rootdir, 'docs';</lang>

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;

The above works but is not the only way or the best way to check status of a file in Pop11. There is a very general procedure sys_file_stat that allows interrogation of a file or directory. The full documentation can be seen in the online documentation (search for sys_file_stat):

http://wwwcgi.rdg.ac.uk:8081/cgi-bin/cgiwrap/wsi14/poplog/pop11/ref/sysio

http://www.poplog.org/docs/popdocs/pop11/ref/sysio

http://www.cs.bham.ac.uk/research/projects/poplog/doc/popref/sysio (Not so well formatted).

Users can easily define special cases of the general procedure.

PowerShell

Test-Path input.txt

Python

Works with: Python version 2.5

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

<lang python>import os

os.path.exists("input.txt") os.path.exists("/input.txt") os.path.exists("docs") os.path.exists("/docs")</lang>

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

Ruby

<lang ruby>File.exist?("input.txt") File.exist?("/input.txt") File.exist?("docs") File.exist?("/docs")</lang>

Smalltalk

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

<lang smalltalk> FileDirectory new fileExists: 'c:\serial'.

  (FileDirectory on: 'c:\') directoryExists: 'docs'.</lang>

In GNU Smalltalk instead you can do:

<lang smalltalk> (Directory name: 'docs') exists ifTrue: [ ... ]

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

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

Standard ML

<lang sml>OS.FileSys.access ("input.txt", []); OS.FileSys.access ("docs", []); OS.FileSys.access ("/input.txt", []); OS.FileSys.access ("/docs", []);</lang>

Tcl

Taking the meaning of the task from the DOS example: <lang tcl>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"

}</lang> Note that these operations do not require the use of file nativename on either Windows or any version of Unix.

Toka

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

UNIX Shell

test -f input.txt
test -f /input.txt
test -d docs
test -d /docs

Visual Basic .NET

Platform: .NET

Works with: Visual Basic .NET 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"))