PowerShell Language Examples

# =============================================================================
# Test files or directories for existence
#
# -Path The path to the file or directory to test for existence.
# =============================================================================
if (Test-Path -Path "C:\path\to\file\or\directory") {
    Write-Host "File exists."
} else {
    Write-Host "File does not exist."
}

# =============================================================================
# Copy one or more files or folders
#
# -Path        The source path of the file or directory to copy.
# -Destination The destination path for the copied file or directory.
# -Recurse     Include the entire contents of the copied directory to the destination.
# =============================================================================

# To copy source a directory recursively to another directory:
Copy-Item -Path "C:\path\to\source" -Destination "C:\path\to\destination" -Recurse

# To copy only "*.txt" files from source to destination:
Copy-Item C:\path\to\source\*.txt C:\path\to\destination

# =============================================================================
# PowerShell Comparison Operators
#
# Description                Operator  Example
# ------------               --------  --------------------------
# Greater than               -gt       1 -gt 2   (Returns $false)
# Less than                  -lt       1 -lt 2   (Returns $true)
# Equals                     -eq       2 -eq 1+1 (Returns $true)
# Not equals                 -ne       3 -ne 1+1 (Returns $true)
# Greater than or equal to   -ge       3 -ge 1+1 (Returns $true)
# Less than or equal to      -le       2 -le 1+1 (Returns $true)
#
# http://www.tomsitpro.com/articles/powershell-comparison-operators-conditional-logic,2-850.html
# =============================================================================

# To select processes related to various web browsers:
Get-Process | Where-Object {($_.Name -eq "iexplore") -or ($_.Name -eq "chrome") -or ($_.Name -eq "firefox")}

# =============================================================================
# PowerShell Where-Object
#
# NOTE: The "$_" default variable is used to indicate the current record being
# passed from the pipeline.
#
# http://www.tomsitpro.com/articles/powershell-comparison-operators-conditional-logic,2-850.html
# =============================================================================

# To list files in the current user profile which have the archive bit set:
Get-ChildItem $env:USERPROFILE -Recurse -Force | Where-Object {$_.Mode -like "*a*"}

# =============================================================================
# If, ElseIf, and Else Statements
#
# http://www.tomsitpro.com/articles/powershell-comparison-operators-conditional-logic,2-850.html
# =============================================================================

# To test if a connection can be reached with "www.google.com":
if (Test-Connection www.google.com -Quiet) {
    Write-Host "Internet connection is live."
}

# Test if a connection can be reached with "www.google.com", if not... try
# connecting to "192.168.0.1"; finally echo "Network connectivity is
# unavailable.", if no Network connectivity.
if (Test-Connection www.google.com -Quiet) {
    Write-Host "Internet connection is live."
} elseif (Test-Connection 192.168.0.1 -Quiet) {
    Write-Host "Only local network connectivity is available."
} else {
    Write-Host "Network connectivity is unavailable."
}

# =============================================================================
# Switch Statements
#
# http://www.tomsitpro.com/articles/powershell-comparison-operators-conditional-logic,2-850.html
# =============================================================================

# To read the day of the week and return whether it is a Weekday or the Weekend:
switch ((Get-Date).DayOfWeek)
{
    "Saturday" {"Weekend"}
    "Sunday" {"Weekend"}
    Default {"Weekday"}
}

# To use the wildcard option with a switch statement to perform matching on days
# that start with the letter "s" for indicating "Weekend".
switch -Wildcard ((Get-Date).DayOfWeek)
{
    "S*" {"Weekend"}
    Default {"Weekday"}
}

#
# Switch to the appropriate server env. based on script arg:
$ENV = $args[0]

if ($ENV -eq $null)
{
    $ENV = "PROD"
}

switch ($ENV)
{
    "PROD"
    {
        $DBServer   = "status.db.prod.dexma.com";
        $DB         = "status";
        $SQLQuery   = "SELECT s.server_name
                       FROM dbo.t_server AS s INNER JOIN
                       dbo.t_monitoring AS m ON s.server_id = m.server_id
                       WHERE (s.active = 1) AND (m.Perfmon = 1) AND (s.environment_id = 0)"
    }
    "DEMO"
    {
        $DBServer   = "status.db.stage.dexma.com";
        $DB         = "statusstage";
        $SQLQuery   = "SELECT s.server_name
                       FROM dbo.t_server AS s INNER JOIN
                       dbo.t_monitoring AS m ON s.server_id = m.server_id
                       WHERE (s.active = 1) AND (m.Perfmon = 1) AND (s.environment_id = 1)"
    }
    "IMP"
    {
        $DBServer   = "status.db.imp.dexma.com";
        $DB         = "statusimp";
        $SQLQuery   = "SELECT s.server_name
                       FROM dbo.t_server AS s INNER JOIN
                       dbo.t_monitoring AS m ON s.server_id = m.server_id
                       WHERE (s.active = 1) AND (m.Perfmon = 1) AND (s.environment_id IN ('2', '9'))"
    }
}

Write-Host $DBServer, $DB, $SQLQuery

# =============================================================================
# Try, Catch and Finally
#
# http://www.vexasoft.com/blogs/powershell/7255220-powershell-tutorial-try-catch-finally-and-error-handling-in-powershell
# =============================================================================

# The last part of Try Catch Finally is the Finally block. This must be defined
# immediately after the Catch block and runs every time, regardless of whether
# there was an error or not. In this way you can perform actions that need to be
# made regardless of whether an operation succeeds or fails. In our example we are
# going to log that a file read was attempted. Our Get-Content line now looks
# like:

Try
{
    $AuthorizedUsers = Get-Content \\FileServer\HRShare\UserList.txt -ErrorAction Stop
}
Catch [System.OutOfMemoryException]
{
    Restart-Computer localhost
}
Catch
{
    $ErrorMessage = $_.Exception.Message
    $FailedItem = $_.Exception.ItemName
    Send-MailMessage -From ExpensesBot@MyCompany.Com -To WinAdmin@MyCompany.Com -Subject "HR File Read Failed!" -SmtpServer EXCH01.AD.MyCompany.Com -Body "We failed to read file $FailedItem. The error message was $ErrorMessage"
    Break
}
Finally
{
    $Time=Get-Date
    "This script made a read attempt at $Time" | out-file c:\logs\ExpensesScript.log -append
}