Today in my PowerShell class, the question came up of how to ask a user for valid information if what they provided is not correct. I did not want to go into parameter validation just yet so I did it in code. This allowed me to demonstration a looping construct and how to use functions inside of your code.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 7 72 73 74 75 76 | Function Get-MyEvents { [cmdletBinding()] Param ( [parameter(Mandatory=$true)] [String]$Logname, [Int]$Newest = 5)
# -- Test-Log ---------------------------------------------------------------- # Test to determine if the log file is valid. # Return code 0 for yes and 1 for no. Function Test-Log { Param ( $LogName ) $ErrorCode = 0 Try { Get-EventLog -LogName $Logname -Newest 1 -ea Stop } Catch { $ErrorCode = 1 } Write-Output $ErrorCode }
# -- Get-Info ---------------------------------------------------------------- # Get the event log info. Function Get-Info { Param($LogName, $Newest) Get-EventLog -LogName $Logname -Newest $Newest }
# -- Main Code --------------------------------------------------------------- # Set the error code to 1 (Unsuccessful) $ErrorCode = 1
# Loop until the Errorcode is 0. Do { # Call Test-Log to retrieve an error code. $ErrorCode = Test-log -LogName $LogName
# If the error code is 1, the ask for a valid file. If ($ErrorCode -eq 1) { $LogName = Read-Host('Please enter a valid log file')
}
} While ($ErrorCode -eq 1)
# Get the log file information. Get-Info -LogName $Logname -Newest $Newest
<# .SYNOPSIS This gets me event.
.DESCRIPTION Gets what ever event log I say.
.PARAMETER Logname This is the name of the logfile you wat to get info from.
.PARAMETER Newest The number of events to return.
.EXAMPLE Get-MyEvents -Logname System -Newest 10 This recovered the newest 10 events from the system log. #> } |
In the Main Code, starting at line 37, I created a variable called $ErrorCode and set it to 1. As long as this variable is equal to 1, the user would be asked for the name of a valid log file.
In line 45, I give the opportunity for that error code to be changed by calling the function Test-Log. This function will attempt to call a record from the event log specified by the user. If it is successful, an ErrorCode of zero is returned. If it is not, an ErrorCode of 1 is returned.
At line 48, if the ErrorCode is 1, the user is prompted for the name of a different log. The loop then executes and the process starts over again.
Line 57 calls another function that actually gets the log information. This function call could have been omitted and just instead move line 34 to line 57. Again, I was demonstrating calling functions.
Comments