Class InstanceLockFile

Namespace

VpnHood.AppLib.App

Assembly

VpnHood.AppLib.App.dll

Provides an app's single-instance lock as a file, in a folder its host names: one only root may write, as the Linux service's, or one the person owns.

public static class InstanceLockFile

Inheritance

object

InstanceLockFile

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

The file is held open with no sharing, which .NET makes an exclusive flock on Linux, and the system lets it go with the process, so a crash leaves no stale lock. On Linux a new lock file is readable and writable by its owner only, as a lock anyone may read is one anyone may hold; a file that is there keeps its permissions.

Fields

FileName

The lock file's name in its folder.

public const string FileName = "instance.lock"

Field Value

string

Methods

IsHeld(IOException)

Returns a value indicating whether an exception from opening a file says another open holds it: a sharing or lock violation on Windows, flock's EWOULDBLOCK on Linux.

public static bool IsHeld(IOException ex)

Parameters

ex IOException

The exception from the open.

Returns

bool

true if another open holds the file; otherwise, false.

Take(string, string)

Takes the lock, making its folder where there is none.

public static FileStream Take(string folderPath, string appId)

Parameters

folderPath string

The folder of the lock file.

appId string

The app's ID, which the exception names.

Returns

FileStream

The open lock file, which holds the lock until it is disposed or the process ends.

Exceptions

AnotherInstanceIsRunningException

Another process holds the lock.

IOException

The file could not be opened for another reason.

UnauthorizedAccessException

The process may not write the folder or the file.