Use a PowerShell Cmdlet to Work with File Attributes

ScriptingGuy1

Summary: Learn how to use the Windows PowerShell cmdlet Set-ItemProperty to work with file attributes.

Hey, Scripting Guy! I often find myself working with file attributes. Our backup program reads the archive flag, and our users are always creating read-only copies of their spreadsheets. I have an old VBScript script that will manipulate file attributes, but I am surprised that Windows PowerShell does not do this. It seems like it should be simple to have a Set-FileAttribute Windows PowerShell cmdlet, but unfortunately it does not seem to exist.

— AD

Hello AD,

Microsoft Scripting Guy Ed Wilson here. One of the cool things about being in Florida during the winter is actually a warm thing. Today, it is 71 degrees Fahrenheit (21.6 degrees Celsius according to my conversion module), and it is sunny. It was such a lovely day that Dr. Scripto decided to head down to the harbor to watch the boats coming in and out.

AD, I will leave Dr. Scripto at the waterfront to work on his tan (he really needs to get out more), and I will tackle your question. In September of last year, I wrote How Can I Unlock a Read-Only File, Edit it, and Make it Read-Only Again? In that post, which was awesome, I worked specifically with the read-only attribute. In this article, I will look at a different way of working with file attributes.

AD, you said you wish that Windows PowerShell had a Set-FileAttribute cmdlet. In fact, it does. It is called Set-ItemProperty. Most people use the Set-ItemProperty cmdlet when working with the registry provider, but the Set-ItemProperty can work with any provider that provides access to item properties. I use the Get-PSProvider cmdlet to detail the Windows PowerShell providers that are currently available to me on my laptop. If I load additional modules or snap-ins, it is possible that additional providers are exposed. Therefore, it is always a good idea to use Get-PSProvider after loading a module or snap-in. The results of Get-PSProvider with no snap-ins or modules loaded appears here:

PS C:\> Get-PSProvider

 

Name                 Capabilities                            Drives

—-                 ————                            ——

WSMan                Credentials                             {WSMan}

Alias                ShouldProcess                           {Alias}

Environment          ShouldProcess                           {Env}

FileSystem           Filter, ShouldProcess                   {C, D}

Function             ShouldProcess                           {Function}

Registry             ShouldProcess, Transactions             {HKLM, HKCU}

Variable             ShouldProcess                           {Variable}

Certificate          ShouldProcess                           {cert}

 

 

PS C:\>

The FileSystem provider works with my C and D drives. To find out what types of item properties are available, I use the Get-ItemProperty to retrieve a file from my FSO folder. The syntax of the command is Get-ItemProperty and the path to the file. The command and its associated output appear here:

PS C:\> Get-ItemProperty -Path C:\fso\a.txt

 

 

    Directory: C:\fso

 

 

Mode                LastWriteTime     Length Name

—-                ————-     —— —-

-a—        12/17/2010   5:08 PM          0 a.txt

 

 

PS C:\>

This is the top-level view of the item properties of the file. To view all of the information that is available, I pipe the results to the Format-List cmdlet, and use the force. This command appears here:

PS C:\> Get-ItemProperty -Path C:\fso\a.txt | Format-list -Property * -Force

 

 

PSPath            : Microsoft.PowerShell.Core\FileSystem::C:\fso\a.txt

PSParentPath      : Microsoft.PowerShell.Core\FileSystem::C:\fso

PSChildName       : a.txt

PSDrive           : C

PSProvider        : Microsoft.PowerShell.Core\FileSystem

VersionInfo       : File:             C:\fso\a.txt

                    InternalName:

                    OriginalFilename:

                    FileVersion:

                    FileDescription:

                    Product:

                    ProductVersion:

                    Debug:            False

                    Patched:          False

                    PreRelease:       False

                    PrivateBuild:     False

                    SpecialBuild:     False

                    Language:

 

BaseName          : a

Mode              : -a—

Name              : a.txt

Length            : 0

DirectoryName     : C:\fso

Directory         : C:\fso

IsReadOnly        : False

Exists            : True

FullName          : C:\fso\a.txt

Extension         : .txt

CreationTime      : 8/17/2009 9:28:43 AM

CreationTimeUtc   : 8/17/2009 1:28:43 PM

LastAccessTime    : 8/22/2009 6:13:01 PM

LastAccessTimeUtc : 8/22/2009 10:13:01 PM

LastWriteTime     : 12/17/2010 5:08:38 PM

LastWriteTimeUtc  : 12/17/2010 10:08:38 PM

Attributes        : Archive

 

 

 

PS C:\>

Okay, that provides a lot of information, but it does not tell me if I can write to the item properties or not. To see this information, I need to use the Get-Member cmdlet. In the place of the previous Format-List command, I use Get-Member. Because I am only interested in properties, I use the membertype parameter and specify property. The revised command and its associated output appear here:

PS C:\> Get-ItemProperty -Path C:\fso\a.txt | Get-Member -MemberType property

 

 

   TypeName: System.IO.FileInfo

 

Name              MemberType Definition

—-              ———- ———-

Attributes        Property   System.IO.FileAttributes Attributes {get;set;}

CreationTime      Property   System.DateTime CreationTime {get;set;}

CreationTimeUtc   Property   System.DateTime CreationTimeUtc {get;set;}

Directory         Property   System.IO.DirectoryInfo Directory {get;}

DirectoryName     Property   System.String DirectoryName {get;}

Exists            Property   System.Boolean Exists {get;}

Extension         Property   System.String Extension {get;}

FullName          Property   System.String FullName {get;}

IsReadOnly        Property   System.Boolean IsReadOnly {get;set;}

LastAccessTime    Property   System.DateTime LastAccessTime {get;set;}

LastAccessTimeUtc Property   System.DateTime LastAccessTimeUtc {get;set;}

LastWriteTime     Property   System.DateTime LastWriteTime {get;set;}

LastWriteTimeUtc  Property   System.DateTime LastWriteTimeUtc {get;set;}

Length            Property   System.Int64 Length {get;}

Name              Property   System.String Name {get;}

 

 

PS C:\>

That is what I was looking for. Notice that in the definition column some of the properties such as Attributes are listed as {get;set;} and others such as Directory are listed as {get;}. Well, if a property is get;set then it is read-write–in other words, I can modify the value. If a property is only get, it is read-only.

The other thing that is useful from the Definition column is the data type that the property accepts. For example, the CreationTime property accepts a System.DateTime object. (I have written a number of posts about working with dates and times in Windows PowerShell on the Hey, Scripting Guy! Blog.) I can obtain a System.DateTime object from the Get-Date cmdlet as shown here:

PS C:\> (Get-Date).gettype()

 

IsPublic IsSerial Name                                     BaseType

——– ——– —-                                     ——–

True     True     DateTime                                 System.ValueType

 

 

PS C:\>

On the other hand, the Attributes property accepts an enumeration value called System.Io.FileAttributes (I have written a number of Hey, Scripting Guy! Blog posts about working with enumerations as well.) To see the enumeration values from System.Io.FileAttributes, I can place the class name in square brackets and use Get-Member, as shown here:

PS C:\> [System.Io.FileAttributes] | Get-Member -Static -MemberType property

 

 

   TypeName: System.IO.FileAttributes

 

Name              MemberType Definition

—-              ———- ———-

Archive           Property   static System.IO.FileAttributes Archive {get;}

Compressed        Property   static System.IO.FileAttributes Compressed {get;}

Device            Property   static System.IO.FileAttributes Device {get;}

Directory         Property   static System.IO.FileAttributes Directory {get;}

Encrypted         Property   static System.IO.FileAttributes Encrypted {get;}

Hidden            Property   static System.IO.FileAttributes Hidden {get;}

Normal            Property   static System.IO.FileAttributes Normal {get;}

NotContentIndexed Property   static System.IO.FileAttributes NotContentIndexed {get;}

Offline           Property   static System.IO.FileAttributes Offline {get;}

ReadOnly          Property   static System.IO.FileAttributes ReadOnly {get;}

ReparsePoint      Property   static System.IO.FileAttributes ReparsePoint {get;}

SparseFile        Property   static System.IO.FileAttributes SparseFile {get;}

System            Property   static System.IO.FileAttributes System {get;}

Temporary         Property   static System.IO.FileAttributes Temporary {get;}

 

 

PS C:\>

I can also use the static GetValues method from the system.enum .NET Framework class (I can leave off the word system when calling the class). This appears here:

PS C:\> [enum]::GetValues([system.io.fileattributes])

ReadOnly

Hidden

System

Directory

Archive

Device

Normal

Temporary

SparseFile

ReparsePoint

Compressed

Offline

NotContentIndexed

Encrypted

PS C:\>

If I want to see the specific value associated with a particular enumeration value, I use the value__ property (keep in mind that is a double underscore at the end of the word value). This technique appears here:

PS C:\> [system.io.fileattributes]::ReadOnly.Value__

1

PS C:\>

Using the Get-EnumValues function from my Enumerations and Values Weekend Scripter post, I obtain the following list of enumerations and their associated values.

Name                           Value                                                               

—-                           —–                                                               

Offline                        4096                                                                

NotContentIndexed              8192                                                                

Device                         64                                                                  

Directory                      16                                                                  

Normal                         128                                                                 

ReparsePoint                   1024                                                                

Archive                        32                                                                  

Encrypted                      16384                                                               

SparseFile                     512                                                                 

System                         4                                                                   

Temporary                      256                                                                 

Hidden                         2                                                                   

ReadOnly                       1                                                                   

Compressed                     2048   

Ok, so far so good. If the attributes were stored as a hash table or as an array, things would be easy. Alas, they are not. They are stored as an old-fashioned bitmask value.

Therefore, to work with them, we need to use old-fashioned techniques, such as the sort thing you learned when you were taking Boolean algebra back at the university. If you are little rusty on your Boolean algebra, you may want to refer to this Hey, Scripting Guy! Blog post. It is sort of like the Karate Kid and “wax on, wax off” only different.

To determine if a file is read-only or not, I need to perform a bitwise AND operation. Therefore, I will use the –BAND operator. Let’s see how that would work out. The file attributes of the a.txt file are ReadOnly and Archive. This is shown here:

PS C:\> (Get-ItemProperty -Path C:\fso\a.txt).attributes

ReadOnly, Archive

PS C:\>

I want to know what that value is so that I can use the Value__ property. However, I also want to know what that value is in binary, so I will use the [convert] class. This technique appears here:

PS C:\> (Get-ItemProperty -Path C:\fso\a.txt).attributes.Value__

33

PS C:\> [convert]::ToString(33,2)

100001

PS C:\>

Everywhere a file attribute is turned on, a 1 appears. Therefore, the value 32 (archive) appears in the sixth position, and read-only (value of 1) appears in the first position. This behaves in a similar way that figuring out subnet masks works. In the table following this paragraph, the first row is the decimal value of the position. In the second row, is the binary representation of the number 33 that I obtained by using the convert class earlier. In the second row, notice there is a 1 in the 32 column, and a 1 in the 1 column. The third row is the binary value of the number 1 (the value of the read-only enumeration). The fourth row represents the results of performing a binary AND (BAND) operation. When performing a Binary AND operation, the rules are thus: 1 –BAND 1 = 1, 1 –BAND 0 = 0, 0 –BAND 0 = 0.

I can use this information to determine if a file has the archive bit or the read-only bit set. This is illustrated here:

PS C:\> (Get-ItemProperty C:\fso\a.txt).attributes -band [io.fileattributes]::Archive

32

PS C:\> (Get-ItemProperty C:\fso\a.txt).attributes -band [io.fileattributes]::ReadOnly

1

PS C:\>

AD, that is all there is to using Set-ItemProperty to retrieve file attributes. Neglected Cmdlet Week will continue tomorrow when I will talk about using Set-ItemProperty to modify file attributes.

I invite you to follow me on Twitter and Facebook. If you have any questions, send email to me at scripter@microsoft.com, or post your questions on the Official Scripting Guys Forum. See you tomorrow. Until then, peace.

Ed Wilson, Microsoft Scripting Guy

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