lsyncd/docs/manual/examples/auto-image-magic/index.md

284 lines
7.2 KiB
Markdown
Raw Normal View History

---
layout: default
title: "Example: Auto-Image-Magic"
tab: "manual/examples"
---
This [example](..) is a layer 1 script to make a special "magic" directory in which image files will be converted automatically therein.
The full script:
{% highlight lua %}
local formats = { jpg = true, gif = true, png = true }
convert = {
delay = 0,
maxProcesses = 99,
action = function(inlet)
local event = inlet.getEvent()
if event.isdir then
-- ignores events on dirs
inlet.discardEvent(event)
return
end
-- extract extension and basefilename
local p = event.pathname
local ext = string.match(p, ".*%.([^.]+)$")
local base = string.match(p, "(.*)%.[^.]+$")
if not formats[ext] then
-- an unknown extenion
log("Normal", "not doing something on ."..ext)
inlet.discardEvent(event)
return
end
-- autoconvert on create and modify
if event.etype == "Create" or event.etype == "Modify" then
-- builds one bash command
local cmd = ""
-- do for all other extensions
for k, _ in pairs(formats) do
if k ~= ext then
-- excludes files to be created, so no
-- followup actions will occur
inlet.addExclude(base..'.'..k)
if cmd ~= "" then
cmd = cmd .. " && "
end
cmd = cmd..
'/usr/bin/convert "'..
event.source..p..'" "'..
event.source..base..'.'..k..
'" || /bin/true'
end
end
log("Normal", "Converting "..p)
spawnShell(event, cmd)
return
end
-- deletes all formats if you delete one
if event.etype == "Delete" then
-- builds one bash command
local cmd = ""
-- do for all other extensions
for k, _ in pairs(formats) do
if k ~= ext then
-- excludes files to be deleted, so no
-- followup actions will occur
inlet.addExclude(base..'.'..k)
if cmd ~= "" then
cmd = cmd .. " && "
end
cmd = cmd..
'rm "'..event.source..base..'.'..k..
'" || /bin/true'
end
end
log("Normal", "Deleting all "..p)
spawnShell(event, cmd)
return
end
-- ignores other events.
inlet.discardEvent(event)
end,
-----
-- Removes excludes when convertions are finished
--
collect = function(event, exitcode)
local p = event.pathname
local ext = string.match(p, ".*%.([^.]+)$")
local base = string.match(p, "(.*)%.[^.]+$")
local inlet = event.inlet
if event.etype == "Create" or
event.etype == "Modify" or
event.etype == "Delete"
then
for k, _ in pairs(formats) do
inlet.rmExclude(base..'.'..k)
end
end
end,
}
sync{convert, source="magicdir", recursive=false}
{% endhighlight %}
This creates a local table of all supported file formats. The file formats are used as keys.
{% highlight lua %}
local formats = { jpg=true, gif=true, png=true, }
{% endhighlight %}
Configures actions to be instant and there is unlimits the amount the conversion to be done at once. Well not unlimited but set the limit pretty high.
{% highlight lua %}
convert = {
delay = 0,
maxProcesses = 99,
{% endhighlight %}
This script uses the _layer 1_ inlet interface altough it greps only single events and not lists. It does this instead of _layer 2_ as it needs to do common operations for all kind of events.
{% highlight lua %}
action = function(inlet)
local event = inlet.getEvent()
{% endhighlight %}
Ignores directories. As using _layer 1_ it has to explicitly discard events it does not spawn actions for.
{% highlight lua %}
if event.isdir then
-- ignores events on dirs
inlet.discardEvent(event)
return
end
{% endhighlight %}
Uses Lua string patterns to extract the file extension from the rest - here called base.
{% highlight lua %}
-- extract extension and basefilename
local p = event.pathname
local ext = string.match(p, ".*%.([^.]+)$")
local base = string.match(p, "(.*)%.[^.]+$")
{% endhighlight %}
Looks the extension up in the formats table. This can be done, since formats are keys in that table. If not an image format it bails out.
{% highlight lua %}
if not formats[ext] then
-- an unknown extenion
log("Normal", "not doing something on ."..ext)
inlet.discardEvent(event)
return
end
{% endhighlight %}
Following actions will done on "Create" and "Modify" events.
{% highlight lua %}
-- autoconvert on create and modify
if event.etype == "Create" or event.etype == "Modify" then
{% endhighlight %}
This script builds a bash command using a string.
{% highlight lua %}
-- builds one bash command
local cmd = ""
{% endhighlight %}
It iterates for all image formats and excludes the one which is the source image.
{% highlight lua %}
-- do for all other extensions
for k, _ in pairs(formats) do
if k ~= ext then
{% endhighlight %}
This is a little trick. It creates Exclusions for the converted images. As this images are not placed in a target directory but right next to the source image in the source directory they would otherwise trigger Create actions as well.
{% highlight lua %}
-- excludes files to be created, so no
-- followup actions will occur
inlet.addExclude(base..'.'..k)
{% endhighlight %}
And for every image to be converted adds the calls to the arguments. It uses ```" || /bin/true "``` to let the shell continue if one conversion fails. In that it chains the conversion with '&&' they will be called sequentially.
{% highlight lua %}
if cmd ~= "" then
cmd = cmd .. " && "
end
cmd = cmd..
'/usr/bin/convert "'..
event.source..p..'" "'..
event.source..base..'.'..k..
'" || /bin/true'
{% endhighlight %}
And eventually it spawns the shell doing the conversions and is finished.
{% highlight lua %}
end
end
log("Normal", "Converting "..p)
spawnShell(event, cmd)
return
end
{% endhighlight %}
For deletions it does technically something similar, but it deletes all other file formats of the image.
{% highlight lua %}
-- deletes all formats if you delete one
if event.etype == "Delete" then
-- builds one bash command
local cmd = ""
-- do for all other extensions
for k, _ in pairs(formats) do
if k ~= ext then
-- excludes files to be deleted, so no
-- followup actions will occur
inlet.addExclude(base..'.'..k)
if cmd ~= "" then
cmd = cmd .. " && "
end
cmd = cmd..
'rm "'..event.source..base..'.'..k..
'" || /bin/true'
end
end
log("Normal", "Deleting all "..p)
spawnShell(event, cmd)
return
end
{% endhighlight %}
and not to forget to nicely discard all other events.
{% highlight lua %}
-- ignores other events.
inlet.discardEvent(event)
end,
{% endhighlight %}
collect is called when the conversions finished. It will remove the temporary excludes again.
{% highlight lua %}
-----
-- Removes excludes when convertions are finished
--
collect = function(event, exitcode)
local p = event.pathname
local ext = string.match(p, ".*%.([^.]+)$")
local base = string.match(p, "(.*)%.[^.]+$")
local inlet = event.inlet
if event.etype == "Create" or
event.etype == "Modify" or
event.etype == "Delete"
then
for k, _ in pairs(formats) do
inlet.rmExclude(base..'.'..k)
end
end
end,
{% endhighlight %}
And finally use the configuration to watch "magicdir".
{% highlight lua %}
sync{convert, source="magicdir", recursive=false}
{% endhighlight %}