I'm using Sysdig to capture some events and have a small chisel (LUA script) to capture and format the events as necessary. On the on_init() I'm requesting fields like so :
f_field = chisel.request_field("<field>")
My question is how can I check if a field exists before requesting it? I'm going to use a new field only just released on 0.24.1 but ideally I'd like my chisel to continue to work on older versions of sysdig without this field. I've tried wrapping the call to chisel.request_field in a pcall() like so :
ok, f_field = pcall(chisel.request_field("<field>"))
and even implementing my own "get_field" function :
function get_field(field)
ok, f = pcall(chisel.request_field(field))
if ok then return f else return nil end
end
f_field = get_field("<field>")
if f_field ~= nil then
-- do something
end
but the error ("chisel requesting nonexistent field <field>") persists.
I can't see a way to check if a field exists but I can't seem to handle the error either. I really don't want multiple versions of my scripts if possible.
Thanks
Steve H
You're almost there. Your issue is in how you're using pcall. Pcall takes a function value and any arguments you wish to call that function with. In your example you're passing the result of the request_field function call to pcall. Try this instead..
ok, f = pcall(chisel.request_field, "field")
pcall will call the chisel method with your args in a protected mode and catch any subsequent errors.
Related
Using the code:
function createNewBody(name,mass)
if not world.body[name]==nil then
print("This body has already been created. Maybe you meant to update it's values?\n")
else
world.body[name]={mass=m,x=0,y=0,xAccel=0,yAccel=0,xR=0,yR=0,properties={gaseous=false,texture=""}}
world.bodies=world.bodies+1
end
end
This code shows no errors, but when I bind createNewBody(moon,1.622) to a key and then use it, it lets me spam the key without showing the error message.
And, yes, I have defined world.bodies and world.body
not world.body[name]==nil is parsed as (not world.body[name])==nil. Since the result of not is a boolean, it is never nil.
Try not(world.body[name]==nil) or world.body[name]~=nil.
I have a WoW/LUA script that I am attempting to start, but it seems to conflict with the Stubby addon, which is a part of the Auctioneer addon, I believe. Here is the message I receive:
Error occured in: Stubby Count: 1 Message: Error: Original call failed
after running hooks for: ChatFrame_OnEvent Usage:
SendChatMessage(text [,type] [,language] [,targetPlayer]) Debug:
(tail call): ? [string ":OnEvent"]:1:
[string ":OnEvent"]:1
Now, the only thing that's happening in the conflicting addon is:
ChatFrame_AddMessageEventFilter("CHAT_MSG_PARTY", partyMsg)
The code within partyMsg is very simple as well:
local function partyMsg(msg,author,language,lineID,senderGUID)
if (store ~= msg) then
SendChatMessage(msg,"SAY",nil,nil);
end
store = msg;
end
Is this error due to two addons both trying to filter the chat frame? If so, how can this be done? It seems odd to me that Blizzard would have such a simple and yet important concept limited to one addon.
I think I see what happened here.
The reference you were using, Events/Communication, shows only the specific parameters for a particular event, regardless of context.
The context is usually an OnEvent handler.
The ChatFrame_AddMessageEventFilter function lets you use the chat frame's OnEvent handler instead of your own for chat frame events, and has well defined parameters for filters you add.
An OnEvent handler might look like:
function Foo_OnEvent(self, event, ...)
A 'ChatFrame' filter must look like this, for the first two parameters:
function Foo_ChatFrameFilter(self, event, msg, ...)
The ChatFrame filter is specific. For OnEvent however, you can make a Lua 'handler' that doesnt care about what frame it came from:
<OnEvent>
MyEventHandler(event, ...)
</OnEvent>
For the sake of completion, I will include the entire source of this addon:
local function partyMsg(someTable,msgType,msg,user,language,...)
if (store ~= msg) then
SendChatMessage(user .. " just said: ".. msg .. " using that sneaky " .. language .. " language.");
end
store = msg;
return false;
end
ChatFrame_AddMessageEventFilter("CHAT_MSG_PARTY", partyMsg)
ChatFrame_AddMessageEventFilter("CHAT_MSG_PARTY_LEADER",partyMsg)
There were a couple issues with the original code:
1) I was using WoWWiki to get my information, and first, I read it incorrectly. lineID and senderGUID are not the 4th and 5th arguments. Then, beyond this, WoWWiki is incorrect on this page in general. The correct arguments are listed above in the source. The first argument, a table, I am unsure of its purpose. In any case, this code now works fully.
I have a problem which i suppose must be very common and most of you would have faced it.
I have written a program in lua, say main.lua which on receiving key event should modify the coordinates and display the geometry figure.
This lua code calls reg.c, where it kind of registers.
Now in reg.c i have a function engine which receives the key pressed and passes it to the lua function responsible for key handling.
But by the time key event comes, lua code is done with the registration and exits, thus the call from engine() becomes illegal memory access leading to segmentation fault.
Also i suppose we can't have lua call hanging in reg function, and call engine function from somewhere else.
Then what should be the solution, please guide me through this.
#jacob: here is the prototype of what i am trying to achieve:
function key_handler() //this function will get the latest key pressed from some other function
{
draw.image();
draw.geometry();
...
...
while(1)
{
//draw Points until some condition goes wrong
}
}
Now, once entered into key_handler, while he is busy drawing the points unless and until the failing condition occurs, i am unable to receive key pressed till that time.
I hope this explanation is much simpler and have made my point, and will help others to understand the problem.
I am really sorry, but i am not good at expressing or making others understand.
One more thing, i ahve followed the C syntax to explain, however this is completely implemented in lua
Your code snippet is still largely non-informative (ideally one should be able to just run your code in a stock Lua interpreter and see your problem). If you're describing a Lua problem, use Lua code to describe it.
However I'm beginning to see where you want to go.
The thing you need to could do is have a coroutine that's called in your key handler, which passes an argument back to your handler:
function isContinue() --just to simulate whatever function you use getting keypresses.
-- in whatever framework you're using there will probably be a function key_pressed or the like.
print('Initialize checking function')
while true do
print('Continue looping?')
local ans = io.read():match('[yY]')
local action
if not ans then
print('Do what instead?')
action = io.read()
if action:match('kill') then -- abort keychecker.
break
end
end
coroutine.yield(ans,action)
end
print('finalizing isContinue')
return nil,'STOP' -- important to tell key_handler to quit too, else it'll be calling a dead coroutine.
end
function key_handler()
local coro = coroutine.create(isContinue)
local stat,cont,action
while true do
print'Draw point'
stat,cont,action = coroutine.resume(coro)
if not stat then
print('Coroutine errored:',cont)
elseif not cont then
print('isContinue interrupted keyhandler')
print("We'll "..action.." instead.")
break
end
end
print('finalizing key_handler')
end
key_handler()
-- type something containing y or Y to continue, all else aborts.
-- when aborting, you get asked what to do instead of continuing,
--- with "kill" being a special case.
This should be self explanatory. You should probably take a good look at Programming in Lua, chapter 9: Coroutines.
The big difficulty (well, if you're not accustomed to collaborative threading) is that a coroutine should yield itself: it's not the calling function that's in charge of returning control.
Hope this helps you.
So I'm looking at how listener taps work. What I've come up with at this point is:
my_tap = Listener.new(nil, "myfilter")
myvar = Field.new("something to look at")
-- then the callback
function my_tap.packet(pinfo)
-- format the time like os.date("%c", pinfo.abs_ts)
-- what else is in pinfo.???
-- lots of stuff
end
I have been unable to find any thorough documentation on what gets exposed to lua via the pinfo parameter to the packet callback. So far I have found *pinfo.abs_ts*. Which is great because tcp.options.timestamp.tsval seems to either be null or contain incorrect / incomplete information all the time.
What exactly gets exposed through pinfo? Is there a list of information I can pull somewhere other than pinfo.abs_ts?
wireshark.org/docs/wsug_html_chunked/lua_module_Pinfo.html seems to describe pretty much everything I was looking for
I'm trying to get a handle on how OOP is done in Lua, and I thought I had a simple way to do it but it isn't working and I'm just not seeing the reason. Here's what I'm trying:
Person = { };
function Person:newPerson(inName)
print(inName);
p = { };
p.myName = inName;
function p:sayHello()
print ("Hello, my name is " .. self.myName);
end
return p;
end
Frank = Person.newPerson("Frank");
Frank:sayHello();
FYI, I'm working with the Corona SDK, although I am assuming that doesn't make a difference (except that's where print() comes from I believe). In any case, the part that's killing me is that inName is nil as reported by print(inName)... therefore, myName is obviously set to nil so calls to sayHello() fail (although they work fine if I hardcode a value for myName, which leads me to think the basic structure I'm trying is sound, but I've got to be missing something simple). It looks, as far as I can tell, like the value of inName is not being set when newPerson() is called, but I can't for the life of me figure out why; I don't see why it's not just like any other function call.
Any help would be appreciated. Thanks!
Remember that this:
function Person:newPerson(inName)
Is equivalent to this:
function Person.newPerson(self, inName)
Therefore, when you do this:
Person.newPerson("Frank");
You are passing one parameter to a function that expects two. You probably don't want newPerson to be created with :.
Try
Frank = Person:newPerson("Frank");