Windows

Problem

You want to update the ReadOnly, Hidden, or System attributes of a file.

Solution

Most of the time, you will want to use the familiar attrib.exe program to change the attributes of a file:

attrib +r test.txt

attrib s test.txt To set only the ReadOnly attribute, you can optionally set the IsReadOnly property on the file:

$file = GetItem test.txt $file.IsReadOnly = $true

To apply a specific set of attributes, use the Attributes property on the file:

Problem

You want to clear the content of a file, or remove that file altogether.

Solution

To clear the content from a file, use the ClearContent cmdlet. Use the RemoveItem cmdlet to remove that file altogether, as shown by Example 171.

Example 171. Clearing content from and removing a file

PS >GetContent test.txt Hello World PS >ClearContent test.txt PS >GetContent test.txt PS >GetItem test.txt

Directory: Microsoft.PowerShell.Core\FileSystem::C:\temp

Problem

You want to find all files last modified before a certain date.

Solution

To find all files modified before a certain date, use the GetChildItem cmdlet to list the files in a directory, and then use the WhereObject cmdlet to compare the LastWriteTime property to the date you are interested in. For example, to find all files created before this year:

GetChildItem Recurse | WhereObject { $_.LastWriteTime lt "01/01/2007" }

Discussion

One of the most common tasks when administering a system is working with its files and directories. This is true when you administer the computer at the command line, and it is true when you write scripts to administer it automatically.

Fortunately, PowerShell makes scripting files and directories as easy as working at the command line—a point that many seasoned programmers and scripters often miss. Aperfect example of this comes when you wrestle with limited disk space and need to find the files taking up the most space.

Discussion

One useful feature of the certificate provider is that it provides a –CodeSign parameter that lets you search for certificates in the certificate store that support code signing. Code signing certificates are not the only kind of certificates, however; other frequently used certificate types are Encrypting File System, Client Authentication, and more.

Example 166 lets you search the certificate provider for certificates that support a given Enhanced Key Usage (EKU).

Example 166. SearchCertificateStore.ps1

Problem

You want to retrieve information about certificates for the current user or local machine.

Solution

To browse and retrieve certificates on the local machine, use PowerShell’s certificate drive. This drive is created by the certificate provider, as shown in Example 165.

Example 165. Exploring certificates in the certificate provider

PS >SetLocation cert:\CurrentUser\ PS >$cert = GetChildItem Rec CodeSign PS >$cert | FormatList

Problem

Your script performs an operation that requires credentials, but you don’t want it to require user interaction when it runs.

Solution

To securely store the credential’s password to disk so that your script can load it automatically, use the ConvertFromSecureString and ConvertToSecureString cmdlets.

Save the credential’s password to disk

Discussion

If your script requires user credentials, you will want to store those credentials in a PowerShell PsCredential object. This lets you securely store those credentials, or pass them to other commands that accept PowerShell credentials. When you write a script that accepts credentials, consider letting the user to supply either a username or a preexisting credential. Example 164 demonstrates a useful approach that allows that. As the framework for this demonstration, the script lets you start a process as another user.

Problem

Your script requires that users provide it with a username and password, but you want to do this as securely as possible.

Solution

To request a credential from the user, use the GetCredential cmdlet: $credential = GetCredential

Discussion

The GetCredential cmdlet reads credentials from the user as securely as possible and ensures that the user’s password remains highly protected the entire time.

Problem

You want to request sensitive information from the user, but want to do this as securely as possible.

Solution

To securely handle sensitive information, store it in a SecureString whenever possible. The ReadHost cmdlet (with the –AsSecureString parameter) lets you prompt the user for (and handle) sensitive information by returning the user’s response as a SecureString:

PS >$secureInput = ReadHost AsSecureString "Enter your private key" Enter your private key: ******************* PS >$secureInput System.Security.SecureString

Discussion