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20-Using-Console-Outputs.md

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Developer Guide: Using Console Outputs

The Icinga PowerShell Framework provides severals Cmdlets to write output into the PowerShell console, ensuring that not only a severity is added but also making it easier to dump object content into the message. In addition these functions are disabled once being called while the Framework is running as background daemon, to ensure the console is not spammed with useless information the user wont see anyway.

The only limitation is that the entire font color can not be changed by using these methods.

Build-In String Formatting

There are many different ways in PowerShell on how to format a string and add object values to them. Some will look nicer than others and by default we mostly use [string]::Format() for this task, as it provides a much better readability.

Following this guideline, a simple output to console might look like this:

Write-Host ([string]::Format('Hello World counter: {0}', 10));

Even while being correct, it is now not as easy anymore to read the line. Of course we can do some formatting to make it readable a lot better:

Write-Host (
    [string]::Format(
        'Hello World counter: {0}',
        10
    )
);

Now the output is much more readbable, but managing this syntax through the entire code structure will possibly affect the entire code again.

The Icinga PowerShell Framework is for this reason providing Cmdlets which will handle the console outputs and the formatting for the user. To simply write plain text to the console, we can do so by using Write-IcingaConsolePlain including an array of objects to add:

Write-IcingaConsolePlain -Message 'Hello World counter: {0}' -Objects 10;

The usage of the {} including the numeric input and how they are parsed is identical to [string]::Format(). -Objects is able to hold an array of elements which will replace the {x} placeholders, depending on the index of the element.

Write-IcingaConsolePlain -Message 'Hello World counter: {0}{1}Maybe adding some newlines as well?' -Objects 10, (New-IcingaNewLine);

Plain Output Without Severity

To write simple content like plugin output, wizard questions or different generic content you can use Write-IcingaConsolePlain. This will print content similar to Write-Host, but allowing the usage of the -Objects argument for easier text formatting:

Write-IcingaConsolePlain -Message 'This is a generic output to console: {0}' -Objects (Get-Random);

This is a generic output to console: 802189320

Output With Severity

To add content to the console inlcuding a severity for better understanding and readability, there are several Cmdlets available following the same structure as the above mentioned. In addition they will how ever print a colored severity in [] before the actual message.

Write-IcingaConsoleNotice

A notice is a simple notification about certain tasks which are processed and to inform the user about something. They will add a Notice message in green color before the output:

Write-IcingaConsoleNotice -Message 'This is a notice output to console: {0}' -Objects (Get-Random);

[Notice]: This is a notice output to console: 292276902

Write-IcingaConsoleWarning

A warning is in general not bad, should how ever inform the user about a possible flaw in configuration, additional required steps or that something did not went as expected. They will add a Warning message in yellow color before the output:

Write-IcingaConsoleWarning -Message 'This is a warning output to console: {0}' -Objects (Get-Random);

[Warning]: This is a warning output to console: 1107808784

Write-IcingaConsoleError

Errors indicate that something went wrong during certain tasks and possibly the intended action did not fully complete properly. They will add a Error message in red color before the output:

Write-IcingaConsoleError -Message 'This is a error output to console: {0}' -Objects (Get-Random);

[Error]: This is a error output to console: 93122235

Write-IcingaConsoleDebug

Debug prints are in general designed for developers or while troubleshooting certain issues. They will add a Debug message in blue color before the message:

Write-IcingaConsoleDebug -Message 'This is a debug output to console: {0}' -Objects (Get-Random);

[Debug]: This is a debug output to console: 1197035604

Note: Debug messages will only be printed if the debug mode of the Icinga PowerShell Framework is enabled. To enable the debug mode, you can use Enable-IcingaFrameworkDebugMode and to disable it Disable-IcingaFrameworkDebugMode. To check if the mode is enabled or disabled you can use Get-IcingaFrameworkDebugMode.