How can I simulate a "locked" file (one which has a write lock)

Question

I am trying to debug a problem where users occasionally have locked files which they try to open. The code appears to have correct exception handling but users are still reporting seeing error messages. How can I simulate a locked file so that I can debug this myself?

EDIT: For Windows.

Janeth

What error messages are they seeing? Do you know for sure that they have locked files when they get the error message? – Trawl

@Ralph, no I don't know if it's a locked file but it seems the most likely. I was also thinking it may be a file which was accessed over a network which lost a connection. This is just my first step in debugging. – Janeth

Also check to see if there are any intermittent system processes which run during that time which may be locking the folder. – Trawl

Some very useful answers to the same question on Superuser, including one to just invoke notepad > fileToLock from the command line (though it'll overwrite the file contents of course, but useful for simulating locks). – Vanvanadate

Answer 1

depends, but in case, MS word locks
if you are wonderig if your application lock files and it do not relase locks:
just modify a bit your aplication (to create a testapp) and never close the file (and keep it runnig)

Debose

Word or Excel were going to be my suggestions, so an upvote well and truly deserved... :) – Harakiri

Luis, thank you for your help. I will give this method a try. :) – Janeth

Answer 2

try this:

( >&2 pause ) >> yourfile.txt

>> opens yourfile.txt in append mode

see this for a reference

Careen

I really like this. Is easier than use big MS-Software to lock my file – Champlain

With PowerShell powershell -c ( >&2 pause ) >> yourfile.txt – Venetis

Answer 3

I used LockFileEx function from the Windows API to write a unittest in Python. This worked well for me (shutil.copy() with a locked target fails).

import win32con
import win32file
import pywintypes

p = "yourfile.txt"
f = file(p, "w")
hfile = win32file._get_osfhandle(f.fileno())
flags = win32con.LOCKFILE_EXCLUSIVE_LOCK | win32con.LOCKFILE_FAIL_IMMEDIATELY

win32file.LockFileEx(hfile, flags, 0, 0xffff0000, pywintypes.OVERLAPPED())

See: https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203%28v=vs.85%29.aspx

Champlain

Answer 4

I am using this command prompt

type yourfile.txt | more

to insert inside yourfile.txt a very long text of "few pages" and want to pipe via | more to batch the insertion. However the file seems to lock, any reason why?

Non