.TH upstart\-file\-bridge 8 2013-03-11 upstart
.\"
.SH NAME
upstart\-file\-bridge \- Bridge between Upstart and inotify
.\"
.SH SYNOPSIS
.B upstart\-file\-bridge
.RI [ OPTIONS ]...
.\"
.SH DESCRIPTION
.B upstart\-file\-bridge
receives information about kernel file events that
.BR inotify (7)
has received and creates
.BR init (8)
events for them.

Supported events exposed to Upstart allow jobs to detect creation,
modification and deletion. See
.BR file\-event (7)
for further details.

The bridge works by querying the
.BR init (8)
daemon at bridge startup time to determine a list of all jobs whose
.B start on
or
.B stop on
conditions reference the
.B file
event. Further, the bridge arranges to be notified automatically when
new jobs are created such that any subsequent jobs which reference the
.B file
event are also handled (as are job deletions).

See \fBinotify\fP(7) and for further details.

.\"
.SH OPTIONS
.\"
.TP
.B \-\-daemon
Detach and run in the background.
.\"
.TP
.B \-\-debug
Enable debugging output.
.\"
.TP
.B \-\-help
Show brief usage summary.
.\"
.TP
.B \-\-user
User-session mode: connect to Upstart via the user session rather than
over the D\-Bus system bus.
.\"
.TP
.B \-\-verbose
Enable verbose output.
.\"
.SH JOB ENVIRONMENT VARIABLES
.TP
.B FILE
Path to file to watch. When run without
.BR \-\-user ","
this must be an absolute path. If
.BR \-\-user
is specified, certain relative path types are supported:
.RS
.IP \[bu] 2
If the path begins with \(aq~/\(aq, 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).
.\"
.IP \[bu]
If the path begins with \(aq./\(aq, \(aq.\(aq will be assumed to be the
users home directory.
.\"
.IP \[bu]
In all other scenarios, if the path does not begin with \(aq/\(aq, it
will be assumed to represent a file below the users home directory.
.P
If the path ends with a slash, it is considered to be a directory which
changes the match behaviour (see below).
.P
If the path is not a directory, the file (but not the directory) portion
of the path may contain wildcard matches. See
.BR fnmatch (3)
and
.BR glob (7)
for further details.
.RE
.\"
.TP
.B EVENT
Event relating to
.B FILE
that job is interested in. If this variable is specified the value must
be set to 
.BR create ", "
.BR modify " or "
.B delete
depending on what type of file event the job is interested in. If
.B FILE
is not specified, the bridge will watch for all types and set this
variable to the appropriate value when emitting the event.
.\"
.SH WATCH TYPE BEHAVIOUR

The bridge emits events depending not only on the value of
.BR EVENT ", "
but also on the entity specified by
.BR FILE ":"
.\"
.SS File

An event will be emitted when the named file is created, modified or
deleted depending on the value of \fBEVENT\fR. If
.B EVENT
is not specified, react to creation, modification and deletion.

If the file already exists when the job is registered, and
.B EVENT
either specifies
.I create
or the variable is not specified, the event will be emitted.
.\"
.SS Directory

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
\fBEVENT\fR. If
.B EVENT
is not specified, react to creation, modification and deletion.

If the directory already exists when the job is registered, and
.B EVENT
either specifies
.I create
or the variable is not specified, the event will be emitted.
.\"
.SS Glob

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
\fBEVENT\fR. If
.B EVENT
is not specified, react to creation, modification and deletion.

If any matches already exist when the job is registered, and
.B EVENT
either specifies
.I create
or the variable is not specified, events will be emitted.
.\"
.SH NOTES

.IP \(bu 4
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
.BR \-\-user "."
.IP \(bu
All job conditions specifying the
.B file
event are multi-shot: if the same file event occurs multiple times, the
bridge will emit an Upstart event each time.
.\"
.SH LIMITATIONS

.IP \(bu 4
Since the bridge currently uses 
.BR inotify (7) "" ","
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
removed
.B cannot
be handled reliably. The following provides advice to minimise
unexpected behaviour:
.RS
.IP \(bu 4
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.
.\"
.IP \(bu
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.
.\"
.IP \(bu
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.
.RE
.IP \(bu
Tilde expansion is only supported for the current user; that is
\(aq~otheruser\(aq will not work.
.\"
.SH AUTHOR
Written by James Hunt
.RB < james.hunt@canonical.com >
.\"
.SH BUGS
Report bugs at 
.RB < https://launchpad.net/ubuntu/+source/upstart/+bugs >
.\"
.SH COPYRIGHT
Copyright \(co 2013 Canonical Ltd.
.PP
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
.SH SEE ALSO
.BR init (5)
.BR init (8)
.BR inotify (7)
.BR file-event (7)