upstart-file-bridge (8) - Linux Man Pages
upstart-file-bridge: Bridge between Upstart and inotify
upstart-file-bridge - Bridge between Upstart and inotify
DESCRIPTIONupstart-file-bridge receives information about kernel file events that inotify(7) has received and creates init(8) events for them.
Supported events exposed to Upstart allow jobs to detect creation, modification and deletion. See file-event(7) for further details.
The bridge works by querying the init(8) daemon at bridge startup time to determine a list of all jobs whose start on or stop on conditions reference the file event. Further, the bridge arranges to be notified automatically when new jobs are created such that any subsequent jobs which reference the file event are also handled (as are job deletions).
See inotify(7) and for further details.
- Detach and run in the background.
- Enable debugging output.
- Show brief usage summary.
- User-session mode: connect to Upstart via the user session rather than over the D-Bus system bus.
- Enable verbose output.
JOB ENVIRONMENT VARIABLES
Path to file to watch. When run without
this must be an absolute path. If
is specified, certain relative path types are supported:
- If the path begins with '~/', the value will be expanded as would be performed by a shell for matching purposes (although when the event is emitted, the original value will be used).
- If the path begins with './', '.' will be assumed to be the users home directory.
- In all other scenarios, if the path does not begin with '/', it will be assumed to represent a file below the users home directory.
If the path ends with a slash, it is considered to be a directory which changes the match behaviour (see below).
- Event relating to FILE that job is interested in. If this variable is specified the value must be set to create, modify or delete depending on what type of file event the job is interested in. If FILE is not specified, the bridge will watch for all types and set this variable to the appropriate value when emitting the event.
WATCH TYPE BEHAVIOUR
An event will be emitted when the named file is created, modified or deleted depending on the value of EVENT. If EVENT is not specified, react to creation, modification and deletion.
An event will be emitted when the named directory is created, modified (files within it are created, modified or deleted) or deleted depending on the value of EVENT. If EVENT is not specified, react to creation, modification and deletion.
One event will be emitted per match when the glob wildcard matches any files in the directory part is created, modified or deleted, depending on the value of EVENT. If EVENT is not specified, react to creation, modification and deletion.
- A single instance of the bridge may be run at the system level, but multiple further instances may be run per user session instance by using the --user.
- All job conditions specifying the file event are multi-shot: if the same file event occurs multiple times, the bridge will emit an Upstart event each time.
Since the bridge currently uses
it is subject to the same limitations; namely that recursive watches
cannot be created reliably in all circumstances. As such, pathological
scenarios such as deep directory trees being created and then quickly
be handled reliably. The following provides advice to minimise
- Attempt to only watch for files to be created, modified or deleted in directories that are guaranteed to already exist at the time the job is registered by the bridge.
- If the system cannot guarantee that the directory will exist at job registration time, arrange for the directory to be created by an Upstart job before the bridge itself starts.
- In user session mode, if a job specifies a file to watch for and that file is created but inaccessible to the user running the bridge, no event will be emitted.
- Tilde expansion is only supported for the current user; that is '~otheruser' will not work.