Clear-Content

Delete all the contents of a file without deleting the file itself.

Syntax
      Clear-Content [ [-path] | [-literalPath] ] string[]
         [-include string[]] [-exclude string[] ]
            [-filter string] [-force] [-credential PSCredential] [-whatIf]
               [-confirm] [-UseTransaction] [CommonParameters]
			   
Key
   -path string[]
       The paths to the items (not containers) from which content is deleted.
       Wildcards are permitted.
       e.g., you may specify a path to one more files, but not a path to a folder.

   -literalPath string[]
       Like Path above, only the value is used exactly as typed.
       No characters are interpreted as wildcards. If the path includes any
       escape characters then enclose the path in single quotation marks.
        
   -include string[]
       Clear only the specified items from the Path. e.g. "*.txt"
        
   -exclude string[]
       Omits the specified items from the Path e.g. "*.txt"
        
   -filter string
       A filter in the provider's format or language. 
       The exact syntax of the filter (wildcard support etc) depends on the provider.
       Filters are more efficient than -include/-exclude, because the provider
       applies the filter when retrieving the objects, rather than having 
       PowerShell filter the objects after they are retrieved.
        
   -force SwitchParameter
       Override restrictions that prevent the command from succeeding, apart
       from security settings. e.g. Force will create file path directories 
       or override a files read-only attribute, but will not change file permissions.
        
   -credential PSCredential
       Uses a credential to validate access to the file. Credential represents
       a user-name, such as "User01" or "Domain01\User01", or a PSCredential
       object, such as the one retrieved using Get-Credential.
       This parameter appears, but it is not yet supported in any PowerShell core 
       cmdlets or providers.
        
   -whatIf
       Describe what would happen if you executed the command without actually
       executing the command.
        
   -confirm
       Prompt for confirmation before executing the command.
 
   -UseTransaction
       Include the command in the active transaction.

   CommonParameters
       -Verbose, -Debug, -ErrorAction, -ErrorVariable, -WarningAction,
        -WarningVariable, -OutBuffer and -OutVariable

Example

Delete the content of all files in the temp directory with the ".log" file name extension,

PS C:>clear-content c:\Temp\* -filter *.log

"Nothing is permanent in this wicked world - not even our troubles" - Charlie Chaplin

Related:

Clear-Item is similar to Clear-Content, but works on aliases and variables, instead of files.
Add-Content - Add to the content of the item
Equivalent bash commands: useradd - Create new user accounts