Searching in http://wiki.mikrotik.com/wiki/Manual:Scripting I could not find the meaning of "no such item" that I sometimes get in scripts and which aborts the script.

Two questions:

1. What's the meaning of that message?
2. Why does it abort a script?

In the mean time I'm going to track down where in the script it terminates.

There are some Google Search results, but to me they're not conclusive: https://www.google.com/search?q=mikrotik+"no+such+item"

--jeroen

It is when your script is trying to access item that does not exist any more. Dynamic entry that was removed etc.

It is when your script is trying to access item that does not exist any more. Dynamic entry that was removed etc.

What do you mean with `etc.`? Can you be more specific? Are there examples that show this going wrong at will? (i.e. reproducible cases).

--jeroen

To be more precise, menu specific "get" and "set" commands (be it "/interface get", "/interface set", "/queue simple get", "/queue simple set", "/ip arp get", "/ip arp set", etc.) throw this error when you give a non existent ID or name as value for the "number(s)" argument.

f.e. is a valid command call (so it's no syntax error), and is semantically equivalent to If a queue with name "test" existed, then the command will return the queue *(as an associative array with each property being array key, and the corresponding value being the member's value).

But if there is no queue with the name "test" at the time the command is actually called, the error is thrown.

If an item (be it a queue, an interface, an ARP item... anything, at any menu) is dynamically generated, and is suddenly removed, you could end up in situations where in one second, a "print" at the menu would tell you the item exists, and a second later, it won't.

An example of dynamically generated items are for example queues, which can be generated from various places, such as the "/ip hotspot" menu - you set up queues for each logged in user, and the queue gets created when the user logs in, and gets removed when the user logs out. Any scripts that do something while the user is logged in may end up in a situation where they attempt to do something, but in the middle of it, the user logs out, causing any future get/set calls related to them to fail.

* Wrong. Sorry. The above would error that you need to specify a property to retrieve. You must specify that as a second argument, at which point the command returns the value of the specified property... The point about the error being thrown when the item doesn't exist is still valid, but my description of "get" was utterly wrong.

To be more precise, menu specific "get" and "set" commands (be it "/interface get", "/interface set", "/queue simple get", "/queue simple set", "/ip arp get", "/ip arp set", etc.) throw this error when you give a non existent ID or name as value for the "number(s)" argument.

Thanks. Now I know what's wrong. I've an associative array with IDs by name. Sometime that ID isn't there, so the `get` won't get it and - instead of the nil I expected - barfs.

--jeroen

A good rule of thumb is to check if an object exist before trying to get/set it.
Quick example: It is however possible to do this in one simple line if you don't care rather it was executed or not. This command will only run if the "[find]" actually returns an object. So it is safe to use in a script, even if there is no interface named "WAN" enabled.

...

Code: Select all

/interface {
    :local varif [find name="WAN" disabled=no]
    :if ([:len $varif] != 0) do={
        :put "Interface \"WAN\" was enabled, disabling."
        set $varif disabled=yes
    } else={
        :put "Interface \"WAN\" was not found or is already disabled."
    }
}

Does `:len` work for `:typeof` returning "nil"?

(I used "nil" which in my case seems to work, but maybe a `:len` check is more general and therefore preferred).

--jeroen

...

Code: Select all

/interface {
    :local varif [find name="WAN" disabled=no]
    :if ([:len $varif] != 0) do={
        :put "Interface \"WAN\" was enabled, disabling."
        set $varif disabled=yes
    } else={
        :put "Interface \"WAN\" was not found or is already disabled."
    }
}

Does `:len` work for `:typeof` returning "nil"?

(I used "nil" which in my case seems to work, but maybe a `:len` check is more general and therefore preferred).

--jeroen

I am not totally sure what is actually preferred.

I always use ":len" to get the count of the objects, this may make a difference if the "[find]" returns an array of objects rather than a single object. At least it is a lot easier to make it work specifically with single objects by doing "[:len $varif] = 1".

Edit: My idea of it returnimg a single object array may be a little off. Since "[/interface find name=WAN]" will return "*0", which has a length of 2.