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Running commands

The normal use of NSClient++ is to request information via queries (or check commands) for example check_cpu. Sometimes you want to do other things like run a command or script without involvement of a check command or based on some other stimuli.

Adding custom Scripts

Adding script are detailed in the CheckExternalScripts module documentation as well as the howto. So here I will only give one example and point out some key points.

To run scripts we need to enable the module:

[/modules]
CheckExternalScripts = enabled

Then we also need to add a script (We will use the long format here for simplicity).

[/settings/external scripts/scripts/my_ok1]
command = scripts\check_ok.bat

Lastly we need to decide how the script should run. To do that there are a set of options we can set.

  • session Should the command be attached to a users session
  • display Should the command be visible to users or not?
  • timeout How long is the command allowed to run?
  • capture output Should we monitor and kill the program or not?
  • user/password Does the script require to run as a special user?

Scheduling commands

Next up we need to run the script the simplest way is to use the scheduler. Normally the scheduler runs a command very x minutes. In some cases we need greater control of when the command should run in which case we can set a specific schedule instead.

In either case we need to start with enabling the scheduler:

[/modules]
Scheduler = enabled

Then we need to add the schedule and we can do this in two way the simple is to specify an interval and the command will be executed for instance every 5 minutes:

[/settings/scheduler/schedules/cmd_interval]
interval = 5m
command = my_ok1

The other option is to use the cron-like schedule to specify more advanced rules to make the command run 47 minutes past every hour for instance:

[/settings/scheduler/schedules/cmd_schedule]
schedule = 47 * * * *
command = my_ok1

Lastly we need to direct the output somewhere

Normally when we use the scheduler we use it for passive monitoring i.e. when we run a check at a given interval and submit the result back. This means we normally send the result to the NSCA client but here we need to redirect the result elsewhere. A few options comes to mind.

  • noop Send the result nowhere (discard it)
  • file Use the SimpleFileWriter to write the result to a file somewhere.
  • script We could create a script which intercepts the result and do whatever we want with it.

Noop

If we do not care about the result the simplest option is to throw it away by setting the target to noop:

[/settings/scheduler/schedules/cmd_1]
schedule = 47 * * * *
command = my_ok1
channel = noop

file

Targeting the file is similar to noop we simply put file as channel:

[/settings/scheduler/schedules/cmd_1]
schedule = 47 * * * *
command = my_ok1
channel = file

But for this to make sense we also need to enable the SimpleFileWriter module and configure it to suite our needs:

[/modules]
SimpleFileWriter = enabled

We can of course configure this module as well but for now we leave it as is which appends the output to output.txt

Full Example

Here is a full example where we every hour run the command and send the result to a file as well as every 5 seconds where we discard it:

[/modules]
CheckExternalScripts = enabled
Scheduler = enabled
SimpleFileWriter = enabled

[/settings/external scripts/scripts/my_ok1]
command = scripts\check_ok.bat

[/settings/scheduler/schedules/cmd_interval]
interval = 5s
command = my_ok1
channel = noop

[/settings/scheduler/schedules/cmd_schedule]
schedule = 18 * * * *
command = my_ok1
channel = file