Ensure that a file exists

From Rosetta Code

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.

[edit] Ada

This example should work with any Ada 95 compiler.

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;

This example should work with any Ada 2005 compiler.

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;

[edit] Aikido

The stat function returns a System.Stat object for an existing file or directory, or null if it can't be found.

 
function exists (filename) {
    return stat (filename) != null
}
 
exists ("input.txt")
exists ("/input.txt")
exists ("docs")
exists ("/docs")

[edit] 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.

Another option is AutoHotkey's IfExist/IfNotExist command

; FileExist() function examples
ShowFileExist("input.txt")
ShowFileExist("\input.txt")
ShowFolderExist("docs")
ShowFolderExist("\docs")
 
; IfExist/IfNotExist command examples (from documentation)
IfExist, D:\
  MsgBox, The drive exists.
IfExist, D:\Docs\*.txt
  MsgBox, At least one .txt file exists.
IfNotExist, C:\Temp\FlagFile.txt
  MsgBox, The target file does not exist.
 
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
}

[edit] BASIC

Works with: QBasic

 
ON ERROR GOTO ohNo
f$ = "input.txt"
GOSUB opener
f$ = "\input.txt"
GOSUB opener
 
'can't directly check for directories,
'but can check for the NUL device in the desired dir
f$ = "docs\nul"
GOSUB opener
f$ = "\docs\nul"
GOSUB opener
END
 
opener:
    e$ = " found"
    OPEN f$ FOR INPUT AS 1
    PRINT f$; e$
    CLOSE
    RETURN
 
ohNo:
    IF (53 = ERR) OR (76 = ERR) THEN
        e$ = " not" + e$
    ELSE
        e$ = "Unknown error"
    END IF
    RESUME NEXT

You can also check for a directory by trying to enter it.

 
ON ERROR GOTO ohNo
d$ = "docs"
CHDIR d$
d$ = "\docs"
CHDIR d$
END
 
ohNo:
    IF 76 = ERR THEN
        PRINT d$; " not found"
    ELSE
        PRINT "Unknown error"
    END IF
    RESUME NEXT

Works with: QuickBasic version 7.1 Works with: PowerBASIC for DOS

Later versions of MS-compatible BASICs include the DIR$ keyword, which makes this pretty trivial.

 
f$ = "input.txt"
GOSUB opener
f$ = "\input.txt"
GOSUB opener
 
'can't directly check for directories,
'but can check for the NUL device in the desired dir
f$ = "docs\nul"
GOSUB opener
f$ = "\docs\nul"
GOSUB opener
END
 
opener:
    d$ = DIR$(f$)
    IF LEN(d$) THEN
        PRINT f$; " found"
    ELSE
        PRINT f$; " not found"
    END IF
    RETURN

[edit] 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.

[edit] C

Works with: POSIX

#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");
  return 0;
}

[edit] C++

Library: boost

#include "boost/filesystem.hpp"
#include <string>
#include <iostream>
 
void testfile(std::string name)
{
  boost::filesystem::path file(name);
  if (exists(file))
  {
    if (is_directory(file))
      std::cout << name << " is a directory.\n";
    else
      std::cout << name << " is a non-directory file.\n";
  }
  else
    std::cout << name << " does not exist.\n";
}
 
int main()
{
  testfile("input.txt");
  testfile("docs");
  testfile("/input.txt");
  testfile("/docs");
}

[edit] C#

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"));

[edit] Clojure

(import '(java.io File))
 
(defn kind [filename]
  (let [f (File. filename)]
    (cond
      (.isFile f)      "file"
      (.isDirectory f) "directory"
      (.exists f)      "other" 
      :else            "(non-existent)" )))
 
(defn look-for [filename]
  (println filename ":" (kind filename)))
 
(look-for "input.txt")
(look-for "/input.txt")
(look-for "docs")
(look-for "/docs")

[edit] Common Lisp

probe-file returns nil if a file does not exist. directory returns nil if there are no files in a specified directory.

(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"))

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

(if (cl-fad:directory-exists-p (make-pathname :directory '(:relative "docs")))
    (print "rel directory exists")
    (print "rel directory does not exist"))

[edit] D

import std.stdio: writeln;
import std.file: exists;
import std.path: sep;
 
void verify(string name) {
    if (name.exists())
        writeln("'", name, "' exists");
    else
        writeln("'", 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");
}

[edit] 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!` })
}

[edit] Factor

: print-exists? ( path -- )
    [ write ": " write ] [ exists? "exists." "doesn't exist." ? print ] bi ;
 
{ "input.txt" "/input.txt" "docs" "/docs" } [ print-exists? ] each

[edit] 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

[edit] 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)

Actually, f90,f95 are able to deal with directory staff:

logical :: dir_e
! a trick to be sure docs is a dir
inquire( file="./docs/.", exist=dir_e )
if ( dir_e ) then
  write(*,*), "dir exists!"
else
  ! workaround: it calls an extern program...
  call system('mkdir docs')
end if

[edit] 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"

[edit] HicEst

   OPEN(FIle=   'input.txt', OLD, IOStat=ios, ERror=99)
   OPEN(FIle='C:\input.txt', OLD, IOStat=ios, ERror=99)
! ...
99 WRITE(Messagebox='!') 'File does not exist. Error message ', ios

[edit] Icon and Unicon

[edit] Icon

Icon doesn't support 'stat'; however, information can be obtained by use of the system function to access command line.

[edit] Unicon

every dir := !["./","/"] do {
   write("file ", f := dir || "input.txt", if stat(f) then " exists." else " doesn't exist.") 
   write("directory ", f := dir || "docs", if stat(f) then " exists." else " doesn't exist.") 
   }

Note: Icon and Unicon accept both / and \ for directory separators.

[edit] J

require 'files'
fexist 'input.txt'
fexist '/input.txt'
direxist=: 2 = ftype
direxist 'docs'
direxist '/docs'

[edit] 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);
   }
}

[edit] JavaScript

Works with: JScript

var fso = new ActiveXObject("Scripting.FileSystemObject");
 
fso.FileExists('input.txt');
fso.FileExists('c:/input.txt');
fso.FolderExists('docs');
fso.FolderExists('c:/docs');

[edit] Liberty BASIC

'fileExists.bas - Show how to determine if a file exists
dim info$(10,10)
input "Type a file path (ie. c:\windows\somefile.txt)?"; fpath$
if fileExists(fpath$) then
    print fpath$; " exists!"
else
    print fpath$; " doesn't exist!"
end if
end
 
'return a true if the file in fullPath$ exists, else return false
function fileExists(fullPath$)
    files pathOnly$(fullPath$), filenameOnly$(fullPath$), info$()
    fileExists = val(info$(0, 0)) > 0
end function
 
'return just the directory path from a full file path
function pathOnly$(fullPath$)
    pathOnly$ = fullPath$
    while right$(pathOnly$, 1) <> "\" and pathOnly$ <> ""
        pathOnly$ = left$(pathOnly$, len(pathOnly$)-1)
    wend
end function
 
'return just the filename from a full file path
function filenameOnly$(fullPath$)
    pathLength = len(pathOnly$(fullPath$))
    filenameOnly$ = right$(fullPath$, len(fullPath$)-pathLength)
end function

[edit] Logo

Works with: UCB Logo

show file? "input.txt
show file? "/input.txt
show file? "docs
show file? "/docs

Alternatively, one can set a file prefix used for subsequent file commands.

setprefix "/
show file? "input.txt

[edit] Mathematica

wd = NotebookDirectory[];
FileExistsQ[wd <> "input.txt"]
DirectoryQ[wd <> "docs"]
 
FileExistsQ["/" <> "input.txt"]
DirectoryQ["/" <> "docs"]

[edit] MAXScript

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

[edit] Modula-3

MODULE FileTest EXPORTS Main;
 
IMPORT IO, Fmt, FS, File, OSError, Pathname;
 
PROCEDURE FileExists(file: Pathname.T): BOOLEAN =
  VAR status: File.Status;
  BEGIN
    TRY
      status := FS.Status(file);
      RETURN TRUE;
    EXCEPT
    | OSError.E => RETURN FALSE;
    END;
  END FileExists;
 
BEGIN
  IO.Put(Fmt.Bool(FileExists("input.txt")) & "\n");
  IO.Put(Fmt.Bool(FileExists("/input.txt")) & "\n");
  IO.Put(Fmt.Bool(FileExists("docs/")) & "\n");
  IO.Put(Fmt.Bool(FileExists("/docs")) & "\n");
END FileTest.

[edit] Objective-C

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");

[edit] OCaml

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

[edit] Oz

declare
  [Path] = {Module.link ['x-oz://system/os/Path.ozf']}
in
  {Show {Path.exists "docs"}}
  {Show {Path.exists "input.txt"}}
  {Show {Path.exists "/docs"}}
  {Show {Path.exists "/input.txt"}}

[edit] 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 there in the root dir';

[edit] 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";'

[edit] Perl 6

'input.txt'.IO ~~ :e;
'docs'.IO ~~ :d;
'/input.txt'.IO ~~ :e;
'/docs'.IO ~~ :d

[edit] PicoLisp

(if (info "file.txt")
   (prinl "Size: " (car @) " bytes, last modified " (stamp (cadr @) (cddr @)))
   (prinl "File doesn't exist") )

[edit] Pike

import Stdio;
 
int main(){
   if(exist("/var")){
      write("/var exists!\n");
   }
 
   if(exist("file-exists.pike")){
      write("I exist!\n");
   }
}

[edit] 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.

[edit] PowerShell

 Test-Path input.txt

[edit] PureBasic

result = ReadFile(#PB_Any, "input.txt")
If result>0 : Debug "this local file exists"
  Else : Debug "result=" +Str(result) +" so this local file is missing"
EndIf 
 
result = ReadFile(#PB_Any, "/input.txt")
If result>0 : Debug "this root file exists"
  Else : Debug "result=" +Str(result) +" so this root file is missing"
EndIf 
 
result = ExamineDirectory(#PB_Any,"docs","")
If result>0 : Debug "this local directory exists"
  Else : Debug "result=" +Str(result) +" so this local directory is missing"
EndIf 
 
result = ExamineDirectory(#PB_Any,"/docs","")
If result>0 : Debug "this root directory exists"
  Else : Debug "result=" +Str(result) +" so this root directory is missing"
EndIf

[edit] Python

Works with: Python version 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")

[edit] R

file.exists("input.txt")
file.exists("/input.txt")
file.exists("docs")
file.exists("/docs")
 
# or
file.exists("input.txt", "/input.txt", "docs", "/docs")

The function file.exists returns a logical value (or a vector of logical values if more than one argument is passed)

[edit] 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

[edit] REBOL

exists? %input.txt
exists? %docs/
 
exists? %/input.txt
exists? %/docs/

[edit] Ruby

File.exist?("input.txt")
File.exist?("/input.txt")
File.exist?("docs")
File.exist?("/docs")

[edit] Scheme

Works with: Scheme version R6RS[1]

(file-exists? filename)

[edit] Seed7

$ include "seed7_05.s7i";
 
const proc: main is func
  begin
    writeln(fileType("input.txt") = FILE_REGULAR);
    writeln(fileType("/input.txt") = FILE_REGULAR);
    writeln(fileType("docs") = FILE_DIR);
    writeln(fileType("/docs") = FILE_DIR);
  end func;

[edit] Slate

(File newNamed: 'input.txt') exists
(File newNamed: '/input.txt') exists
(Directory root / 'input.txt') exists
(Directory newNamed: 'docs') exists
(Directory newNamed: '/docs') exists

[edit] 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.

[edit] Standard ML

OS.FileSys.access ("input.txt", []);
OS.FileSys.access ("docs", []);
OS.FileSys.access ("/input.txt", []);
OS.FileSys.access ("/docs", []);

[edit] 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"
}

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

[edit] Toka

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

[edit] UNIX Shell

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

[edit] Vedit macro language

Vedit allows using either '\' or '/' as directory separator character, it is automatically converted to the one used by the operating system.

// In current directory
if (File_Exist("input.txt")) { M("input.txt exists\n") } else { M("input.txt does not exist\n") }
if (File_Exist("docs/nul", NOERR)) { M("docs exists\n") } else { M("docs does not exist\n") }
 
// In the root directory
if (File_Exist("/input.txt")) { M("/input.txt exists\n") } else { M("/input.txt does not exist\n") }
if (File_Exist("/docs/nul", NOERR)) { M("/docs exists\n") } else { M("/docs does not exist\n") }

[edit] 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"))