Powershell Nuggets

Here are a few Powershell nuggets for beginners to digest.

First thing that might trip you up is the Execution Policy built into Powershell. I’ve turned this off on my development machine but it’s obviously advised to have it enabled on production machines. That aside, it’s easy to turn off…

If you’re using Vista you may need to run Powershell in Administrator mode to allow the required registry change. To make my environment a little more user friendly I’ve setup a Powershell Profile with the following code

cd C:\Users\Rhys\Documents\powershell
function prompt {"PS: $(get-date)>"}

This changes the current working directory to my scripts folder and keeps the prompt reasonably short.

Write text files with Powershell

Just look how easy it is to write text files in Powershell.

$text = "abcdefghijklmnopqrstuvwxyz1234567890"

# Method 1: Write file using set-content.
# Just pipe the contents of the variable
$text | set-content -encoding ascii alphabet.txt

# Method 2: Use out-file to append the for loop index to a file
for($i = 0; $i -lt 10; $i++)
{
	$i | out-file -filePath "forLoop.txt" -encoding ascii -append
}

After executing this you should have 2 new .txt files in your working directory.

List & Count Files by Extension with Powershell

This script will list filenames and their sizes before displaying a total count of those files. Just change the extension in the script if you want to work with different file types.

#####################################################
# Filename: DirectoryTextFiles.ps1 #
# Author: Rhys Campbell #
# Description: Lists all .txt files in the current #
# directory, with their length in bytes, and #
# displays a total count of .txt files. #
# Date: 2009-04-22 #
#####################################################

$count = 0;

$files = dir *.txt

foreach($file in $files)
{
	$count++;
	$filename = $file.name
	$fileLength = $file.Length
	echo "The text file $filename is $fileLength bytes.";
}

echo "===================================================="
echo "Total text files in this directory = $count";

Get the Twitter Public Timeline with Powershell

One line of code is all is takes with Powershell!

([xml](new-object net.webclient).DownloadString("http://twitter.com/statuses/public_timeline.rss")).rss.channel.item | format-table title,link

Ping multiple computers with Powershell

###############################################
# Filename: ComputerPinger.ps1 #
# Author: Rhys Campbell #
# Description: Pings multiple computers #
# supplied in the $args array. #
# Date: 2009-04-16 #
###############################################

# Simple ping for each computer
# supplied in the $args array
foreach($computer in $args)
{
	ping $computer;
}

Count Databases On Multiple Servers

Those of you that are still with me get to see the exciting stuff. This script will count databases, and see if SQLAGENT is running, on multiple servers. Just specify each server on the command line. This script uses Windows authentication so bear this in mind for each of your servers. It’s with examples like this that I hope you start to see the power and possibilities of Powershell.

################################################################################
# Filename: MultiHostDatabaseCount.ps1 #
# Description: #
# Author: Rhys Campbell #
# Date: 2009-04-15 #
# Usage: FullPathToFile\MultiHostDatabaseCount.ps1 server1 server2 server3 etc #
################################################################################

trap
{
	"Eek! An exception occured."
	write-error $("TRAPPED: " + $_.Exception.GetType().FullName);
	write-error $("TRAPPED: " + $_.Exception.Message);
	# Terminate the script on error
	exit
}

# Loop through each server name supplied in the $args array
foreach($arg in $args)
{
	# Connection string
	$connectionString = "Server=$arg;Database=master;Trusted_Connection=True;"
	# setup the connection object
	$SqlConn = New-Object -Typename System.Data.SqlClient.SqlConnection
	$SqlConn.ConnectionString = $connectionString
	# Open the connection
	$SqlConn.open();
	$cmd = "SELECT COUNT(*) AS cnt FROM sys.databases";
	# Create the sql command object
	$SqlCmd = New-Object System.Data.SqlClient.SqlCommand $cmd, $SqlConn
	# Run the query
	$result = $SqlCmd.ExecuteReader()
	# Move pointer to the first row
	$result.Read() > $null
	# Get db count
	$dbCount = $result[0]
	# Close the connection
	$SqlConn.close()
	# Reopen the connection
	$SqlConn.open()
	# New command to get SQLAGENT state
	$cmd = "xp_servicecontrol 'querystate', 'SQLSERVERAGENT'"
	# Create the sql command object
	$SqlCmd = New-Object System.Data.SqlClient.SqlCommand $cmd, $SqlConn
	# Run the query
	$result2 = $SqlCmd.ExecuteReader()
	# Move pointer to the first row
	$result2.Read() > $null
	# Get db count
	$SQLAGENT = $result2[0]
	# Print out the database count for the host
	echo "$arg hosts $dbCount databases. The SQLAGENT Service is $SQLAGENT"
	# Clean up
	$SqlConn.close()
}

I hope to check out the huge range of Powershell Extensions and Tools available to do some really cool things. I’ve had a quick play with Quest Software’s PowerGUI. This looks pretty good but I try to stay away from fancy tools until I’ve learned the basics of a language well. I’m looking forward to working with Powershell scripting. I see some great possibilities for…

Multiple SQL Server & MySQL management. Check multiple servers in one script! Check backups, disk space, virtually anything!
Adhoc access to many data sources; including text files, rss feeds, databases, Active Directory.
Producing troubleshooting scripts for less experienced support staff.