How to purposefully exclusively lock a file?

Question

I want to hold an exclusive lock on a file so it cannot be read or written by anything else. Is there a simple Windows tool or command to do this?

I suppose the tool or utility would implement the LockFileEx Windows Function.

Note: I've tried text editors like Notepad and Notepad++ on a text file but they don't hold an exclusive lock on it.

Why not just make one? Also, how long should they hold the lock? Should they wait for some event? — user541686, Jun 09 '11 at 02:38
I considered programming one but figured there's a quick tool, editor or command I can use. On superuser not all users are programmers. http://bit.ly/lXT6ey I didn't want to go the Stackoverflow route with this question. Am testing the behaviour of an app when it can't access files. — John K, Jun 09 '11 at 02:53
I might be able to make one for you -- just lemme know when the lock should be released. — user541686, Jun 09 '11 at 02:57
see also my similar question http://superuser.com/questions/519389/flock-command-for-windows — eadmaster, Dec 18 '12 at 02:50
Apparently, editors such as Notepad and Notepad++ don't even keep the file open non-exclusively. — John, Aug 27 '14 at 15:31

score 182 · Answer 1 · edited Oct 18 '13 at 13:15

182

Simpler solution: In the directory of interest run from cmd line:

notepad >filetolock

As re-directed stdout, it will remain locked until the application (notepad) is terminated.

Note that the "filetolock" will be overwritten by the re-direct, so you probably don't want to use an existing file of any importance. An empty "filetolock" won't matter to the application you're trying to test, as the app won't be able to open it anyway.

edited Oct 18 '13 at 13:15

Kevin Panko

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answered Sep 24 '13 at 20:09

user257114

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use append redirect instead to now overwrite filetolock: `notepad >>filetolock` – eadmaster Apr 18 '14 at 01:38
5

very useful solution, no need to install anything – Aprillion May 01 '14 at 16:06
7

This is a much better solution than downloading more freeware. – BenCr Oct 06 '14 at 12:30
2

Great sulution. The locked file can't be deleted, **but it can be copied.** – marsh-wiggle Jan 05 '15 at 13:23
11

Still works on Windows 10. Should be the accepted answer – vinczemarton Oct 14 '15 at 09:38
Extremely useful, works perfectly in Windows 8.1 too. – Spikeh Apr 08 '16 at 12:40
15

For some reason this has to be executed in cmd.exe. It doesn't work in PowerShell. File is created and notepad is opened but you can still delete file despite notepad being open. I tested this on both Windows Server 2012 and Windows 10. – Ville Salonen Mar 23 '17 at 06:56
Great for testing exception handling for File.WriteAllText and co. – TechAurelian Sep 20 '17 at 10:00
2

this method only place a write lock, not a read lock – MtwStark Jan 11 '18 at 15:34
Do not forget to run as Administrator. That did it for me. – Bonez024 Feb 27 '18 at 19:17
@VilleSalonen: any ideas why it doesn't work from PowerShell? I have found https://stackoverflow.com/questions/1215260/how-to-redirect-the-output-of-a-powershell-to-a-file-during-its-execution and the answers there (namely `powershell notepad >filetolock` and `notepad | Out-File C:\path\to\filetolock`) seem to be working without problems. I suspect, that the interpretation of `>` is internally differently dispatched in cmd and in PowerShell, but I cannot find any confirmation on that. – D. Kovács Jun 04 '18 at 10:46
And check that file is not read-only or you'll get an Access Denied. Tested on Windows 10. – saastn Jul 10 '20 at 15:54
Damn, after decades coding I just learned a new trick! – Maximiliano Rios Jan 25 '21 at 20:31
You can use any other program also. For example, running `pause > filetolock` in CMD will lock the file until you press any key. – Nulano Aug 06 '23 at 18:33

score 57 · Answer 2 · edited Dec 06 '21 at 15:55

57

Lock a file without 3rd party tools, no changes to the file being locked and file can't even be copied

This PowerShell script is a quote from an answer to a similar question.

# Specify the file name
$fileName = "C:\myfile.txt"

# Open the file in read only mode, without sharing (I.e., locked as requested)
$file = [System.io.File]::Open($fileName, 'Open', 'Read', 'None')

# Wait in the above (file locked) state until the user presses a key
Write-Host "Press any key to continue ..."
$null = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyDown")

# Close the file
$file.Close()

Edit: quoting a very usefull comment:

While testing this I found that you can also just use

[System.io.File]::Open('c:\myfile.txt', 'Open', 'Read', 'None')

which will keep the file open until you close PowerShell

edited Dec 06 '21 at 15:55

StackzOfZtuff

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answered Dec 28 '14 at 20:17

marsh-wiggle

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i found this as the only working solution. Both notepad and EasyFileLocker methods doesn't totally lock the file and still can be copied (tested on Windows 10) – HypeZ May 16 '16 at 08:26
For Powershell ISE use `[void](Read-Host 'Press Enter to continue')` instead of `$host.UI.RawUI.ReadKey(...)` as ReadKey is not supported in the pseudo-console in Powershell ISE. – Simon Elms Sep 07 '16 at 04:14
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While testing this I found that you can also just use `[System.io.File]::Open('c:\myfile.txt', 'Open', 'Read', 'None')` which will keep the file open until you close PowerShell – user665780 Sep 15 '20 at 14:54

score 32 · Answer 3 · answered Jun 10 '11 at 08:11

32

Open it with MS-Excel... this app locks a file while open.

answered Jun 10 '11 at 08:11

Ice

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And I thought Excel was useful before! – Scott Stafford Oct 04 '12 at 19:58

score 23 · Accepted Answer · edited Oct 13 '11 at 04:58

23

Try Easy File Locker (freeware).

enter image description here

edited Oct 13 '11 at 04:58

Gaff

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answered Oct 13 '11 at 04:50

David

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Does not work on Windows 2003 – Eric Bonnot Oct 29 '14 at 14:38
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This application doesn't appear to "Lock" files so much as change the permission on the file. This is an important distinction if you're trying to test how your application handles files being actively opened/locked by another application. In my case this application did not work. The 'notepad > file' solution should be the answer here. – javajavajavajavajava Jul 20 '15 at 14:48
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DOES NOT WORK ON Windows 10. And uninstallable. Beware!! – Shahar Prish Oct 08 '18 at 06:16
This app caused multiple blue screen crashes on Windows 10. This app is also designed for creating inaccessible files via permission changes, not file locking by processes. Using FileLocker from @RRKbabxW3's answer worked perfectly. – Jordan Mack Feb 05 '19 at 02:49
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Goes to blue screen of death on Windows 10. – TonySalimi Sep 13 '19 at 12:30
its asking for password and i didn't set one? – Decoder94 May 24 '21 at 16:03
@david its asking for password and i didn't set one? – Decoder94 May 24 '21 at 16:04

score 17 · Answer 5 · answered Aug 13 '14 at 15:59

17

FileLocker is a freeware/open source command line tool.

Usage:

FileLocker [/T LockTime] [/I] [/K] [/Q] file [file...]

/T LockTime     Time in milliseconds to lock the file
/I              Infinite locking until process is killed (default)
/K              Lock file until key is pressed
/Q              Be quiet.

answered Aug 13 '14 at 15:59

RRKbabxW3

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This worked for me where other solutions did not – cowlinator Jan 31 '18 at 00:46
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Note that on Windows 10, it must be run As Administrator. – cowlinator Jan 31 '18 at 00:53
compared to lots of other googled solution, this immediately worked, and also it completely locked the file (also read access was locked, not just writing). – ndbd Nov 20 '20 at 20:35

score 5 · Answer 6 · edited May 23 '17 at 12:41

5

I cannot write comments, so I add my info this way:

https://stackoverflow.com/questions/5860542/how-can-i-simulate-a-locked-file-one-which-has-a-write-lock

EDIT: summary of the other question:

pause command: ( >&2 pause ) >> file2lock.txt
MS programs like word or excel locks too (works for text-files)
Programatically use LockFileEx (windows API) with LOCKFILE_EXCLUSIVE_LOCK and LOCKFILE_FAIL_IMMEDIATELY

edited May 23 '17 at 12:41

Community

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answered Sep 14 '16 at 07:59

Mayra Delgado

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This is the only one that worked for me in Windows Server 2019+ – Markive Mar 06 '23 at 07:44

score 3 · Answer 7 · answered Mar 12 '19 at 10:31

I second the solution by marsh-wiggle. Here's my version of the script:

# This is lock_file.ps1
[CmdletBinding()]
Param(
  [Parameter(Mandatory=$False)]
  [string]$my_file_path
)
if (!$my_file_path){
   Write-Host "Parameter my_file_path is missing, quitting."
   [Environment]::Exit(1)
}
$my_file_exists = Test-Path $my_file_path -pathType Leaf
If ($my_file_exists) {
   #Open the file in read only mode, without sharing (I.e., locked as requested)
   $my_open_file = [System.io.File]::Open($my_file_path, 'Open', 'Read', 'None')
   #Wait in the above (file locked) state until the user presses a key
   Write-Host "Press any key to continue ..."
   $null = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyDown")
   #Close the file
   $my_open_file.Close()
} else {
   Write-Host "Parameter mismatch, file doesn't exist." 
}

You can call it from cmd like this:

powershell -ExecutionPolicy Unrestricted -file lock_file.ps1 "path\to\file_to_lock.txt"

score 1 · Answer 8 · answered Nov 10 '15 at 19:29

Here is how I replicate user behavior of a locked file for bug testing.

Dim s As New StreamReader("C:\test\sampleFile.txt")

I add that line to my unit test to lock the file and then run the test in debug mode to replicate bad behavior when a given file is locked.

I still do not know how my business users are locking the given file. As you said, notepad cannot lock it exclusively.

Luckily, declaring a streamreader locks a file exclusively unless you specify otherwise.

score 0 · Answer 9 · answered Sep 14 '19 at 09:00

For testing Robocopy ERROR "access denied" I just removed read-access for the user. Would that work?

For windows 10 this can be readily done from the command line

chmod 'u-r' lockfile

For windows 7, you can use file explorer security properties.

score -2 · Answer 10 · edited Dec 11 '17 at 16:30

Replace 'Your-Password-Here' with your password, and save this script as Locker.bat

*cls
@ECHO OFF
title Folder Locker
if EXIST "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}" goto UNLOCK
if NOT EXIST Locker goto MDLOCKER
:CONFIRM
echo Are you sure u want to Lock the folder(Y/N)
set/p "cho=>"
if %cho%==Y goto LOCK
if %cho%==y goto LOCK
if %cho%==n goto END
if %cho%==N goto END
echo Invalid choice.
goto CONFIRM
:LOCK
ren Locker "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}"
attrib +h +s "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}"
echo Folder locked
goto End
:UNLOCK
echo Enter password to Unlock folder
set/p "pass=>"
if NOT %pass%==Your-Password-Here goto FAIL
attrib -h -s "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}"
ren "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}" Locker
echo Folder Unlocked successfully
goto End
:FAIL
echo Invalid password
goto end
:MDLOCKER
md Locker
echo Locker created successfully
goto End
:End*

When you run the batch file, it will present you with the 'Are you sure u want to Lock the folder(Y/N)' prompt; type Y and press enter and the folder will be locked.

Run the the batch file again, and enter your password and the folder and all your files will be unlocked again.

This only works on folders, and worse, it *renames* the folder. That won't do at all. — I say Reinstate Monica, Feb 19 '18 at 15:02

How to purposefully exclusively lock a file?

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