Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 132 Part I Laying the Foundation However, a string object variable with the value of ‘7’ can be created as follows: PS> [string] $counter = ‘7’ Variables can also contain objects or collections. Collections are just a group of objects, such as an array. It’s easy to create a collection just by assigning a list of values to a variable, like this: PS> $stuff = 1,2,4,6,8 The list of numbers is grouped into a collection of integer objects and placed in the variable $stuff. Individual elements within the collection can be accessed by using their ordinal number: PS> $stuff[2] 4 PS> Addressing individual elements of an array is nice, but the power of collections is realized by being able to iterate through the members of the collection. PowerShell offers two versions of foreach logic, the first being a cmdlet to which a collection is piped, like this: PS> $stuff | foreach-object {write-output $_} 1 2 4 6 8 Notice the variable $_, which is defined as the current object in the set of objects the cmdlet is iterating through. The other version is the foreach language element, which enables naming of the member: PS> foreach ($thing in $stuff) {write-output $thing} 1 2 4 6 8 Now, within the script block operating on the members of the collection, conditions can be checked. For example, if the script should only operate on elements with a value not greater than 4, the script would read as follows: PS> $stuff | foreach-object { if ($_ -gt 4) {break} else {write-output $_}} 1 2 4 Table 7-1 shows most of the comparison operators within PowerShell. 132 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 133 Scripting with PowerShell 7 TABLE 7-1 Comparison Operators Operator Description -lt less than -le less than or equal to -gt greater than -ge greater than or equal to -eq equal to -ne not equal to -like like wildcard pattern matching Suppose you have a text file called servers.txt that contains a list of servers, one server name per line. The file might resemble something like this: SQLTBWS SQLTBXP SQLTBW7 SQLPROD1 SQLPROD2 By using the Get-Content cmdlet, this list of servers can easily be brought into a PowerShell variable as a collection by issuing the following command: $servers = Get-Content ‘servers.txt’ Each element in the collection can be addressed by its ordinal number, so the first item is referenced by $servers[0], the second item by $servers[1], and so on. This ability to create collections will come in handy later in this discussion. Comments, always good in any language, are specified in PowerShell 1.0 by using the pound (#) charac- ter, with the comments following that character on the line. (PowerShell 2.0 will support an additional comment operator, enabling multi-line comments, e.g., <# Multi-Line Comment #>.) Referencing the $servers collection, each element in the collection is a string object, and string objects have a Length property, so the element can be tested to determine whether it has a value using the following commands: if ($servers[0].Length -gt 0) { #work } 133 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 134 Part I Laying the Foundation Control flow is handled by the commands shown in Table 7-2. To help with logic flow, PowerShell provides a group of ‘‘object’’ cmdlets, as shown in Table 7-3. For example, in the earlier example of the $servers collection, the collection can be iterated through using the following commands: $servers | Foreach-Object { Write-Output $_ } TABLE 7-2 Control Flow Commands If if ($val -eq "target") { #work } For For ($i=0; $i -lt 10; $i++) { #work } Switch Switch ($val) { "Val1" { #work } "Val2" { #work } } Do Until Do { #work } Until ($val -eq "target") Do While Do { #work } While ($val -eq "target") While While ($val -eq "target") { #work } 134 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 135 Scripting with PowerShell 7 TABLE 7-3 Object cmdlets in PowerShell Cmdlet Alias Description ForEach-Object % Executes once for each member in the collection Where-Object ? Filters objects based on conditions Select-Object select Pipes only the specified properties Sort-Object sort Sorts the objects Tee-Object tee Sends the objects in two directions These cmdlets will be very useful when scripting. For example, they enable iteration through a collection of properties in objects, as shown here: get-service | where-object {$_.Status -eq "Running"} The preceding produced the following results: Status Name DisplayName Running 1-vmsrvc Virtual Machine Additions Services Running AeLookupSvc Application Experience Lookup Service Running Browser Computer Browser Running CryptSvc Cryptographic Services Running DcomLaunch DCOM Server Process Launcher Running Dhcp DHCP Client Running dmserver Logical Disk Manager Running Dnscache DNS Client Running ERSvc Error Reporting Service Running Eventlog Event Log Running EventSystem COM+ Event System Running helpsvc Help and Support Running HTTPFilter HTTP SSL Running lanmanserver Server Running lanmanworkstation Workstation Running LmHosts TCP/IP NetBIOS Helper Running MSDTC Distributed Transaction Coordinator Running MsDtsServer100 SQL Server Integration Services 10.0 Running MSOLAP$INST01 SQL Server Analysis Services (INST01) Running MSSQL$INST01 SQL Server (INST01) Running MSSQL$INST02 SQL Server (INST02) In this example, PowerShell sifts through the current services on the system and returns only those services that are currently running. Note the braces ({}) delimiting the operation of the where-object 135 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 136 Part I Laying the Foundation cmdlet. These braces allow embedded operations within loop-type structures; and together with the script content between them, are referred to as a script block. Most important, help is always available using the Get-Help cmdlet. It can also be called using the help or man aliases. Either way, help can be obtained for any cmdlet; and it will return syntax, description, and related links. Get-Help has options to return normal, full, detailed, or examples. To get help on any cmdlet, type Get-Help followed by the cmdlet. To get help on Get-Help,typethe following: PS> Get-Help Get-Help NAME Get-Help SYNOPSIS Displays information about Windows PowerShell cmdlets and concepts. SYNTAX Get-Help [[-name] <string>] [-component <string[]>] [-functionality <string[]>] [-role <string[]>] [-category <stri ng[]>] [-full] [<CommonParameters>] Get-Help [[-name] <string>] [-component <string[]>] [-functionality <string[]>] [-role <string[]>] [-category <stri ng[]>] [-detailed] [<CommonParameters>] Get-Help [[-name] <string>] [-component <string[]>] [-functionality <string[]>] [-role <string[]>] [-category <stri ng[]>] [-examples] [<CommonParameters>] Get-Help [[-name] <string>] [-component <string[]>] [-functionality <string[]>] [-role <string[]>] [-category <stri ng[]>] [-parameter <string>] [<CommonParameters>] DETAILED DESCRIPTION The Get-Help cmdlet displays information about Windows PowerShell cmdlets and concepts. You can also use "Help {<cm dlet name> | <topic-name>" or "<cmdlet-name> /?". "Help" displays the help topics one page at a time. The "/?" disp lays help for cmdlets on a single page. RELATED LINKS Get-Command Get-PSDrive Get-Member 136 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 137 Scripting with PowerShell 7 REMARKS For more information, type: "get-help Get-Help -detailed". For technical information, type: "get-help Get-Help -full". Creating scripts While it’s sometimes useful to enter ad hoc commands into PowerShell to evaluate system state or other information, the real power of PowerShell comes with writing scripts. A good collection of scripts to perform normal administrative functions is a sign of an effective administrator. For example it’s a good idea to have information about the physical servers on which SQL Server is running. Windows Management Instrumentation (WMI) provides this information through simple queries, available to PowerShell through the Get-WMIObject cmdlet (aliased as gwmi). A simple script to gather this information is shown in Listing 7-1. In this script, four different WMI classes are polled, and their results are piped into the select-object cmdlet (aliased as select), where the specific properties needed are retrieved. Those results are then piped into the format-list cmdlet for presentation. LISTING 7-1 Get System Info #getsysinfo.ps1 # Use WMI queries to retrieve information about the computer, operating # system and disk devices gwmi -query "select * from Win32_ComputerSystem" | select Name, Model, Manufacturer, Description, DNSHostName, Domain, DomainRole, PartOfDomain, NumberOfProcessors, SystemType, TotalPhysicalMemory, UserName, Workgroup | format-list gwmi -query "select * from Win32_OperatingSystem" | select Name, Version, FreePhysicalMemory, OSLanguage, OSProductSuite, OSType, ServicePackMajorVersion, ServicePackMinorVersion | format-list gwmi -query "select * from Win32_PhysicalMemory" | select Name, Capacity, DeviceLocator, Tag | format-table -Autosize gwmi -query "select * from Win32_LogicalDisk where DriveType=3" | select Name, FreeSpace, Size | format-table -Autosize When this script is run on a server it will return results like this: Name : SQLTBWS Model : Virtual Machine Manufacturer : Microsoft Corporation Description : AT/AT COMPATIBLE DNSHostName : sqltbws 137 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 138 Part I Laying the Foundation Domain : WORKGROUP DomainRole : 2 PartOfDomain : False NumberOfProcessors : 1 SystemType : X86-based PC TotalPhysicalMemory : 1073192960 UserName : SQLTBWS\Administrator Workgroup : Name : Microsoft Windows Server 2003 R2 Enterprise Edition|C:\WINDOWS| Version : 5.2.3790 FreePhysicalMemory : 340816 OSLanguage : 1033 OSProductSuite : 274 OSType : 18 ServicePackMajorVersion : 2 ServicePackMinorVersion : 0 Name Capacity DeviceLocator Tag Physical Memory 16777216 DIMM1 Physical Memory 0 Physical Memory 16777216 DIMM2 Physical Memory 1 Physical Memory 16777216 DIMM2 Physical Memory 2 Physical Memory 16777216 DIMM2 Physical Memory 3 Name FreeSpace Size C: 60792463360 68705730560 E: 16124747776 17173573632 F: 17087807488 17173573632 Anytime a set of commands will be used repeatedly, it’s useful to encapsulate those commands in a function. Functions must be defined before they can be used, because PowerShell is an interpretive language and doesn’t ‘‘read ahead’’ to see what functions might be defined later. Best Practice B egin all PowerShell scripts with the set of functions that will be used in the script, with the main part of the script listed at the very end. PowerShell cannot forward-reference function code, so the function must have been read before it’s called in the main part of the script. 138 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 139 Scripting with PowerShell 7 The basic format of a function is as follows: Function MyFunction { #work } This, of course, doesn’t do anything. Between the braces the real work needs to be coded, but most often functions need parameters. You can add functions in a number of ways, but two ways are most commonly used. The first, most obvious, format is like this: Function MyFunction ($param) { #work } This works fine, but the recommended method is to use a param block within the function, which enables the specification of multiple parameters, the specification of the data type for each parameter, and even default values for each parameter: Function MyFunction { param ( [int]$x = 7, [int]$y = 9 ) #work } The GetSysInfo.ps1 script shown in Listing 7-1 is useful when run on an individual server, but wouldbeevenmoresoifitcouldberunagainstallservers in the data center. By putting the working code from GetSysInfo.ps1 into a function (and adding the –computername parameter to each Get-WMIObject command within the function to specify which server to run the command against) it’s possible to iterate through the set of servers in the $servers collection discussed earlier. Listing 7-2 shows exactly how to do this. The function with the calls to the four WMI classes is defined first, followed by the main part of the script. Note that before attempting to get the server information, the main part of the script uses the WMI class Win32_PingStatus to determine whether the com- puter is reachable through the network. This saves time because the script doesn’t attempt to run the four main queries against a server that doesn’t respond. LISTING 7-2 ServerStatus.ps1 function getwmiinfo ($svr) { gwmi -query "select * from Win32_ComputerSystem" -computername $svr | select Name, Model, Manufacturer, Description, DNSHostName, Domain, DomainRole, PartOfDomain, NumberOfProcessors, 139 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 140 Part I Laying the Foundation SystemType, TotalPhysicalMemory, UserName, Workgroup | format-list gwmi -query "select * from Win32_OperatingSystem" -computername $svr | select Name, Version, FreePhysicalMemory, OSLanguage, OSProductSuite, OSType, ServicePackMajorVersion, ServicePackMinorVersion | format-list gwmi -query "select * from Win32_PhysicalMemory" -computername $svr | select Name, Capacity, DeviceLocator, Tag | format-table -Autosize gwmi -query "select * from Win32_LogicalDisk where DriveType=3" -computername $svr | select Name, FreeSpace, Size | format-table -Autosize } $servers = get-content ‘servers.txt’ foreach ($server in $servers) { $results = gwmi -query "select StatusCode from Win32_PingStatus where Address = ‘$server’" $responds = $false foreach ($result in $results) { if ($result.statuscode -eq 0) { $responds = $true break } } if ($responds) { getwmiinfo $server } else { Write-Output "$server does not respond" } } The results of this script look like this: Name : SQLTBWS Model : Virtual Machine Manufacturer : Microsoft Corporation Description : AT/AT COMPATIBLE DNSHostName : sqltbws Domain : WORKGROUP DomainRole : 2 140 www.getcoolebook.com Nielsen c07.tex V4 - 07/23/2009 9:03pm Page 141 Scripting with PowerShell 7 PartOfDomain : False NumberOfProcessors : 1 SystemType : X86-based PC TotalPhysicalMemory : 1073192960 UserName : SQLTBWS\Administrator Workgroup : Name : Microsoft Windows Server 2003 R2 Enterprise Edition|C:\WINDOWS| Version : 5.2.3790 FreePhysicalMemory : 341320 OSLanguage : 1033 OSProductSuite : 274 OSType : 18 ServicePackMajorVersion : 2 ServicePackMinorVersion : 0 Name Capacity DeviceLocator Tag Physical Memory 16777216 DIMM1 Physical Memory 0 Physical Memory 16777216 DIMM2 Physical Memory 1 Physical Memory 16777216 DIMM2 Physical Memory 2 Physical Memory 16777216 DIMM2 Physical Memory 3 Name FreeSpace Size C: 60792463360 68705730560 E: 16124743680 17173573632 F: 17088528384 17173573632 SQLTBXP does not respond SQLTBW7 does not respond SQLPROD1 does not respond SQLPROD2 does not respond The day after I wrote this script for this book, I was on a consulting engagement that called for collecting server data for more than 70 SQL Server instances, and I was able to use this script as a starting point for my data collection. After I completed the script I wrote an article about it for the Simple-Talk newsletter. The article is available at www.simple-talk.com/sql/database-administration/let-powershell-do-an-inventory- of-your-servers/ . Errors are handled using a Trap function. The Try-Catch mechanism for error handling will be added to PowerShell in version 2.0, but for the time being the best method is to create a Trap function at the beginning of the script, like this: Function Error_Handler { $errmsg = "Error Category: " + $error[0].CategoryInfo.Category $errmsg = $errmsg + ". Error Object: " + $error[0].TargetObject 141 www.getcoolebook.com . have a text file called servers.txt that contains a list of servers, one server name per line. The file might resemble something like this: SQLTBWS SQLTBXP SQLTBW7 SQLPROD1 SQLPROD2 By using the. Integration Services 10.0 Running MSOLAP$INST01 SQL Server Analysis Services (INST01) Running MSSQL$INST01 SQL Server (INST01) Running MSSQL$INST02 SQL Server (INST02) In this example, PowerShell. SSL Running lanmanserver Server Running lanmanworkstation Workstation Running LmHosts TCP/IP NetBIOS Helper Running MSDTC Distributed Transaction Coordinator Running MsDtsServer100 SQL Server Integration