class QFileSystemWatcher#

The QFileSystemWatcher class provides an interface for monitoring files and directories for modifications. More…

Synopsis#

Methods#

def __init__()
def addPath()
def addPaths()
def directories()
def files()
def removePath()
def removePaths()

Signals#

def directoryChanged()
def fileChanged()

Note

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Detailed Description#

QFileSystemWatcher monitors the file system for changes to files and directories by watching a list of specified paths.

Call addPath() to watch a particular file or directory. Multiple paths can be added using the addPaths() function. Existing paths can be removed by using the removePath() and removePaths() functions.

QFileSystemWatcher examines each path added to it. Files that have been added to the QFileSystemWatcher can be accessed using the files() function, and directories using the directories() function.

The fileChanged() signal is emitted when a file has been modified, renamed or removed from disk. Similarly, the directoryChanged() signal is emitted when a directory or its contents is modified or removed. Note that QFileSystemWatcher stops monitoring files once they have been renamed or removed from disk, and directories once they have been removed from disk.

Notes:

On systems running a Linux kernel without inotify support, file systems that contain watched paths cannot be unmounted.

The act of monitoring files and directories for modifications consumes system resources. This implies there is a limit to the number of files and directories your process can monitor simultaneously. On all BSD variants, for example, an open file descriptor is required for each monitored file. Some system limits the number of open file descriptors to 256 by default. This means that addPath() and addPaths() will fail if your process tries to add more than 256 files or directories to the file system monitor. Also note that your process may have other file descriptors open in addition to the ones for files being monitored, and these other open descriptors also count in the total. macOS uses a different backend and does not suffer from this issue.

See also

QFile QDir

__init__([parent=None])#

Parameters:: parent – QObject

Constructs a new file system watcher object with the given parent.

__init__(paths[, parent=None])

Parameters:

paths – list of strings
parent – QObject

Constructs a new file system watcher object with the given parent which monitors the specified paths list.

addPath(file)#

Parameters:: file – str
Return type:: bool

Adds path to the file system watcher if path exists. The path is not added if it does not exist, or if it is already being monitored by the file system watcher.

If path specifies a directory, the directoryChanged() signal will be emitted when path is modified or removed from disk; otherwise the fileChanged() signal is emitted when path is modified, renamed or removed.

If the watch was successful, true is returned.

Reasons for a watch failure are generally system-dependent, but may include the resource not existing, access failures, or the total watch count limit, if the platform has one.

Note

There may be a system dependent limit to the number of files and directories that can be monitored simultaneously. If this limit is been reached, path will not be monitored, and false is returned.