If your working a lot with parameters and inputs you need to check if variables have the right value and are not “null”.
The normal if -eq “$null” doesn’t work:
if ($varibalename -eq $null) { Write-Host "variable is null" }
Now how you can check that (check if $variablename has $null as value):
if (!$variablename) { Write-Host "variable is null" }
And here if you wanna check if $variablename has any value except $null:
if ($variablename) { Write-Host "variable is NOT null" }
For some reason your Powershell script should send a Tweet. With this function Powershell will send a message to Twitter.
function Send-Tweet($Message)
{
#Twitter Login
$Twitter_UserName = "yourname"
$Twitter_Password = "yourpassword"
$Twitter_URL = "https://twitter.com/statuses/update.xml?status="
$Twitter_Request = [System.Net.WebRequest]::Create($Twitter_URL + $Message)
$Twitter_Request.credentials= New-Object System.Net.NetworkCredential($Twitter_UserName,$Twitter_Password)
$Twitter_Request.method= "POST"
$Twitter_Request.contentType = "application/x-www-form-urlencoded"
$Twitter_Request.GetResponse().statusCode # return the status code of the request
}
You can now call this function and add a message
Send-Tweet "This is my first Tweet from Powershell"
If you need a interactive script you can simply use this (seen by Bhargav’s IT Playground)
function Send-Tweet($Message,$UserName){
if($Message-eq$null){$Message=Read-Host"Enter your tweet"}
if($Username-eq$null){$Username=read-host"Enter your twitter username"}
if($Password-eq$null)
{
$Password=read-host-assecurestring"Enter your twitter password"
$marshal=[Runtime.InteropServices.Marshal]
$Password=$marshal::PtrToStringAuto($marshal::SecureStringToBSTR($Password))
}
$url="https://twitter.com/statuses/update.xml?status=$Message"
$request=[System.Net.WebRequest]::Create($url)
$request.credentials=New-Object System.Net.NetworkCredential($UserName,$Password)
$request.method="POST"
$request.contentType ="application/x-www-form-urlencoded"
$request.GetResponse().statusCode # return the status code of the request}
In my company we started to use XML files as configuration files. So we use it for some configurations of servers or automation for our robots. In Powershell there is a pretty easy way for parsing XML. In Powershell there is an object type for XML, so you just can use the get-content Cmdlet to read the XML file into the object.
$xmldata = get-content "C:\XMLFiles\mydata.xml"
When you create a function for reading XML files you also can set the XML object to global.
$global:xmldata = get-content "C:\XMLFiles\mydata.xml
Now $xmldata is a object which includes all the data of the mydata.xml.
Lets view the content of the mydata.xml file. We need this to understand the following commands.
<TodoList ID = “Week21″>
<Task action=”create” ID=”1″>
<Name>Peter</Name>
<Dept>Administration</Dept>
<email>peter@contoso.com</email>
</Task><Task action=”create” ID=”2″>
<Name>Thomas</Name>
<Dept>Administration</Dept>
<email>thomas@contoso.com</email>
</Task><Task action=”delete” ID=”3″>
<Name>Steve</Name>
<Dept>IT</Dept>
<email>steve@contoso.com</email>
</Task></TodoList>
Now we wanna get all unique Accounts listed
$xmldata.TodoList.Task | %{$_.Name} | select-object -unique
Peter
Thomas
Stefan
We can also create a new object for a specific Task
[Object]$xmltask2 = $xmldata.TodoList.Task | Where-Object {$_.ID -eq "2"}
Now we have a new object with data from Task ID 2. If we wanna see the name from this we just use the same command with the new object
$xmltask3 | %{$_.Name}
Thomas
We can do a lot more with this, but I will bring this up in the next blog posts.
Using the Invoke-Expression Cmdlet:
The Invoke-Expression cmdlet provides one way to run a script from within Windows PowerShell.
Invoke-Expression c:\scripts\test.ps1
or
& c:\scripts\test.ps1
And you also can run a function in your Powershell Script by a variable. This is something really important when you work with dynamic scripts:
Invoke-Expression -command ($Function_Name)
you even can send dynamic parameters to this function:
Invoke-Expression -command ($Function_Name + ' $Function_Parameters')