This PowerShell function `Wait-ForFileReady` is designed to determine when a...

August 28, 2025 at 05:12 PM

function Wait-ForFileReady {
    param([string]$Path, [int]$TimeoutSec = 60)
    $sw = [Diagnostics.Stopwatch]::StartNew()
    $lastSize = -1
    while ($sw.Elapsed.TotalSeconds -lt $TimeoutSec) {
        try {
            if (-not (Test-Path -LiteralPath $Path)) { Start-Sleep -Milliseconds 200; continue }
            $info = Get-Item -LiteralPath $Path -ErrorAction Stop
            # If size is stable for 1 second and file can be opened for Read, consider it ready
            if ($info.Length -eq $lastSize -and $lastSize -ge 0) {
                $fs = [System.IO.File]::Open($Path, [System.IO.FileMode]::Open, [System.IO.FileAccess]::Read, [System.IO.FileShare]::Read)
                $fs.Close()
                return $true
            }
            $lastSize = $info.Length
        } catch { }
        Start-Sleep -Seconds 1
    }
    return $false
}

This PowerShell function Wait-ForFileReady is designed to determine when a file located at a specified path is "ready" to be accessed. It does this by implementing the following logic:

Parameters:

[string]$Path: The full path to the file to monitor.
[int]$TimeoutSec = 60: The maximum number of seconds to wait for the file to become ready (default is 60 seconds).

Process:

Initialize Stopwatch: A stopwatch ($sw) is started to track the elapsed time.
Monitor File Path:
- If the file does not exist at the given path (Test-Path), the function waits briefly (200 milliseconds) and then checks again.
- If the file exists, it queries the file's metadata using Get-Item.
Determine File Readiness:
- The function checks if the file's size ($info.Length) has stabilized (i.e., the size is the same as the last recorded size for at least 1 second).
- If the size is stable and the file can be successfully opened in Read mode (using [System.IO.File]::Open), the function considers the file ready and exits with $true.
Timeout Handling:
- If the file does not become ready before the $TimeoutSec limit is reached, the function exits with $false.

Purpose:

This function is useful for scenarios where a process needs to wait for a file to be completely created, written, or copied into a location before further actions are taken on it (e.g., reading or processing the file). It prevents accessing a file prematurely, which could result in errors or incomplete data.

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