PowerShell Scripting  -WhatIf and -Confirm

Introduction to PowerShell Scripting -WhatIf and -Confirm

WhatIf and confirm are two great commands for testing complicated scripts without risking the code running amok.  For example, if you decide to delete files by using a script containing wildcards, there could be all manner of unexpected side effects.  By employing PowerShell, and appending -whatIf you get a preview of would happen without risking any damage.

WhatIf Topics

• Mission to delete files
• -WhatIf example
• -Confirm example
• Summary of -WhatIf and -confirm in PowerShell

Mission to delete files

Let us take a real life example, we wish to delete files, but because we are using wildcards we are concerned about deleting the wrong type of file.  Instead of gung-ho Guy deleting the files - ready or not, we will take the cautious approach and append -whatIf.  The result is PowerShell completes the command and shows us the result, but does not delete any files.  Incidentally, I cannot find a delete verb in PowerShell, there is however, a remove verb.

-whatIf example

By adding -whatIf at the end of the command we are saying to PowerShell: 'Just test, don't actually make any permanent changes'.  Please note, there could be serious consequences if you don't use the -whatIf switch.  If you don't understand what you are doing, you could delete all your .txt files.

A breakdown of what the above script achieves

get-Childitem  (Rather like dir)
c:\ (Location to start)
-include *.txt  (The pattern to look for)
-recurse (Search subdirectories)
| remove-Item (The equivalent of Delete)
-whatIf (PowerShell please test, but don't actually complete the operation, in this case, just show me which files with a .txt extension would be deleted if I removed the -whatIf).

Another example of -whatIf

-confirm example

Here is another parameter that you append to a 'normal' script - confirm.  It really is a case of confirm by name, and confirm by nature.  PowerShell says to you: 'Do you really want to do this?'

The result of -confirm is that PowerShell presents you with choices, however, remember this is now 'live' therefore if you press [Y] or [A] then files will be deleted.

[Y] Yes [A] Yes to all  [N] No  [L] No to all [S] Suspend

Summary of -whatIf and -confirm in PowerShell

Once you have used -whatIf and -confirm you will think, 'Why don't all scripting languages have these safety features'.

See also PowerShell syntax

• PowerShell Home   • Syntax   • Loops   • Variables  • What If   • Functions   • Replace

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