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95 lines
4.5 KiB
Markdown
95 lines
4.5 KiB
Markdown
---
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layout: default3
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title: "Config Layer 2: Advanced onAction"
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short: "Config Layer 2"
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---
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While Layer 4 and 3 feel like normal configuration files, Layer 2 and 1 enter the realm of coding. It is thus supposed you have some coding knowledge when using Layer 2 or 1.
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Instead of designating actions as strings as in Layer 3 Lua functions can used to do some small scripts right within Lsyncd.
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This example will convert any file with the suffix ".ps" created in a directory into a PDF.
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{% highlight lua %}
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autopdf = {
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onCreate = function(event)
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log("Normal", "got an onCreate Event")
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if string.ends(event.pathname, ".ps") then
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spawn(event, "/usr/bin/ps2pdf", event.sourcePath)
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end
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end
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}
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{% endhighlight %}
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The function can take any valid Lua code.
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Lsyncd provides you a set of functions to be used in user scripts.
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log(Category, ...)
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------------------
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Logs a message into file/stdout/syslog. The first parameter is the logging category all others are strings to be logged. A logging category must start with a capital letter. "Normal" and "Error" are standard categories for log messages. All others are categories for debugging.
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spawn(Event, Binary, ...)
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--------------------------
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Spawns a new process associated with the event (or event list, see below) as first parameter. The second parameter specifies a binary to call. All others are arguments for the binary.
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If the third parameter is "<", then along with fourth parameter they will not be passed as arguments to the binary. The fourth parameter is a string that will piped through stdin to the binary.
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Do not use Lua's ```os.execute``` as opposed to Lsyncd's ```spawn()``` it will block and thus block the whole Lsyncd daemon until the command is completed. Lsyncd's ```spawn``` on the other hand returns immediately while the child process runs.
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spawnShell(Event, Command, ... )
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--------------------------------
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The same as spawn(), only it will invoke a shell. Any parameters are referred as $1, $2, $3 and so on in the command.
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By the way, this is the simple implementation of spawnShell:
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{% highlight lua %}
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function spawnShell(agent, command, ...)
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return spawn(agent, "/bin/sh", "-c", command, "/bin/sh", ...)
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end
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{% endhighlight %}
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terminate(exitcode)
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-------------------
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Lets Lsyncd terminate with ```exitcode```.
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event
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-----
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Variables of the actions are given by the _event_ field. It has following fields.
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|Field|Meaning|
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|:----|:----|
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| event.config | the configuration as called with sync{} |
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| event.inlet | see [layer 1](../layer1/) about inlets |
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| event.etype | the event type. Can be 'ATTRIB', 'CREATE', 'MODIFY', 'DELETE', 'MOVE' |
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| event.status | the status of the event. 'wait' when it is ready to be spawned and 'active' if there is a process running associated with this event |
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| event.isdir | true if the event relates to a directory |
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| event.name | the filename, directories end with a slash |
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| event.basename | the filename, directories do not end with a slash |
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| event.path | see ^path of [Layer 3](../layer3/#all-possible-variables) |
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| event.pathname | see ^pathname of [Layer 3](../layer3/#all-possible-variables) |
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| event.source | see ^source of [Layer 3](../layer3/#all-possible-variables) |
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| event.sourcePath | see ^sourcePath of [Layer 3](../layer3/#all-possible-variables) |
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| event.sourcePathname | see ^sourcePathname of [Layer 3](../layer3/#all-possible-variables) |
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| event.target | see ^target of [Layer 3](../layer3/#all-possible-variables) |
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| event.targetPath | see ^targetPath of [Layer 3](../layer3/#all-possible-variables) |
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| event.targetPathname | see ^targetPathname of [Layer 3](../layer3/#all-possible-variables) |
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onMove actions have two events as parameter, the origin and the destination of the move.
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This example will tattle about all moves within the observed directory tree.
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{% highlight lua %}
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tattleMove = {
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onMove = function(oEvent, dEvent)
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log("Normal", "A moved happened from ",
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oEvent.pathname, " to ", dEvent.pathname)
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end,
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}
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{% endhighlight %}
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Action functions have to be short and fast. They are running right within Lsyncd's one and only main thread. If you have to do any more time consuming calculations _spawn{}_ a child process instead.
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There can only be one child process associated to a event.
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Layer 3 is nothing else than Lsyncd automatically write Layer 2 functions for you on initialization. Start Lsyncd with ```-log FWrite``` on a Layer 3 configuration to see what functions it dynamically writes and loads for you. Thus Layer 3 and 2 can also be be mixed at will.
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