File Locker

A debugger's tool: open any file in fmShareExclusive mode so no other application can read or write it. Useful when you need to reproduce a file-in-use error path that your own program has to handle.

What it does

You point File Locker at any file on disk. It opens a stream on that file in exclusive-share mode and keeps it open until you close the program. Any other application that tries to read, write, or delete that file will fail with a sharing violation.

When you need it

• Testing your own program's behaviour when a file is unexpectedly locked
• Reproducing a customer's "file is in use" bug report in a controlled way
• Verifying retry-on-locked logic with deterministic locking
• Forcing other apps to wait, fall back, or surface a clear error message

Features

• Single executable — portable, no installer
• One file at a time
• Lock released the instant you close the program
• Useful in combination with debugger breakpoints

System requirements

• Windows 7, 8, 10, 11
• A few MB of free RAM
• Under 1 MB of disk space