Powershell Simplified Part 9: Powershell Tips

Some Powershell tips and tricks to make your life easier,

1. Working with write-host,

write-host "starting "nonewline          # don't add a new line after the string
write-host "iexplore.exe" -foregroundcolor red -backgroundcolor yellow  # change text color
write-host "`nIs a new line`n"             # `n is a new line
write-host "`tIs a tab"                    # `t is a tab
write-host ("{0} : {1}" -f "formatting a string", "works!")    # format a string
write-host "this is a double-quote `""
write-host "this is a single-quote '" 

2. Powershell also has an equivalent of C#’s string literal, called here-string,

$a = @"
This can have any char: ``~!@#$%^&*()_+{}|\;'"<>?[]/     # note that ` needs to be escaped with another `
"@
write-host $a

3. To get the current script name,

write-host $MyInvocation.MyCommand.Name         # get current script name
write-host $MyInvocation.MyCommand.Definition   # get current script full directory 

4. Sometimes we need to suppress a Powershell cmd output,

$path = "c:\program files\internet explorer\signup\test"
new-item $path -itemtype directory              # will output some extra information to stdout

# to suppress the output, try one of these,
new-item $path -itemtype directory > $null      # preferred way
new-item $path -itemtype directory | out-null
$null = new-item $path -itemtype directory
[void] (new-item $path -itemtype directory) 

5. Strings and variable/expression expansions,

$a = "test"
write-host 'this is a $a'            # single-quote won't expand the variable
write-host "this is a $a"            # only double-quotes will process variable substitutions 

$file = get-item $env:windir\explorer.exe
write-host "file version: $file.versioninfo.productversion"        # variables get expanded in strings not property expressions
write-host "file version: $($file.versioninfo.productversion)"     # use $() for expression expansion 

6. Getting keyboard input,

write-host "Press any key to continue ..."
$x = $host.UI.RawUI.ReadKey("NoEcho, IncludeKeyDown") 
write-host "Pressed $($x.character)"
switch($x.virtualkeycode) {           # for special keys, map the virtualkeycode,
    13 { write-host "Enter" } 
    16 { write-host "Shift" } 
}

7. We can add custom C# types to Powershell using add-type. However add-type has a limitation that once you load an assembly into a .NET application, the types it contains are not released until the application shuts down, so running the sample below again will result in "Add-Type : Cannot add type. The type name ‘myClass’ already exists."

add-type -typedefinition @" 
  using System;
  public class myClass { 
      private string _test = "He said: "; 
      private static string test = "She said: ";

      public string Test { 
          get { return this._test; } 
          set { this._test = value; } 
      } 

      public string DoSomething(string str) { 
          return this.Test + str; 
      }

      public static string DoSomethingElse(string str) { 
          return test + str; 
      }
  } 
"@ 

[myClass]::DoSomethingElse("test")   # invoke the static method
$a = new-object myClass
$a.DoSomething("test")               # invoke the instance method
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About soumya chattopadhyay
I live and work in Seattle, WA. I work with Microsoft technologies, and I'm especially interested in C#.

One Response to Powershell Simplified Part 9: Powershell Tips

  1. Pingback: Powershell Simplified Series « I.Net

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