PowerShell Cheat Sheet (3) - Functions, Error Handling, Files

Functions

# Defining
function Get-Length($text)
{
  Write-Hist $text.Length
}

# Executing
Get-Length "Lukasz"

# Passing reference
function Change-Value([ref] $x)
{
  $x = 5;
}

# Executing
$x = 1
Change-Value ([ref]$x)

# Functions with pipeline
function Proc-Pipeline()
{
  begin {}
  process {}
  end {}
}

# Filters
filter Filter-Files
{
  if($_.Name -like "*.cs")
  {
    return $_
  }
}

# Support for switches
function Get-Help ()
{
  param([switch]$x, [switch]$y)
  if($x.IsPresent)
  {
  }
}

Error Handling

# Trap
function With-Trap($x, $y)
{
  $z = $x/$y
  trap [System.DivideByZeroException]
  {
  }
  trap
  {
    Write-Host $_.ErrorID
    Write-Host $_.Exception.Message
    continue
    # break
  }
}

Files

# Getting the content
$content = Get-Content "file.txt"

# Getting lines
$content[0]
$content[1]

# Joining
$content_as_string = [String]::Join($sep, $content)

# Wildcard support
$content = Get-Content "*.txt"

# Writing to file (with overwrite)
Set-Content -Value "Text to file" -Path "file.txt"

# Append to file
Add-Content -Value "Some more text" -Path "file.txt"

# Remove file
Remove-Item "file.txt"

# CSV files
Export-Csv
$header = "Col1", "Col2"
$content = Import-Csv "File.csv" -Header $header

# XML files - write
$content = "<html><body>Body text</body></html>"
$content | Out-File "file.xml"

# XML files - read
$content = New-Object xml
$content.Load("file.xml")

# Read data
$body_text = (@(content.html.body)[0]).Clone()