Dir Function

Artykuł
11/16/2012

Returns a string representing the name of a file, directory, or folder that matches a specified pattern or file attribute, or the volume label of a drive.

The My.Computer.FileSystem Object gives you greater productivity and performance in file I/O operations than the Dir function. See My.Computer.FileSystem.GetDirectoryInfo Method for more information.

Public Overloads Function Dir() As String
' -or-
Public Overloads Function Dir( _
    ByVal PathName As String, _ 
    Optional ByVal Attributes As FileAttribute = FileAttribute.Normal _
) As String

Parameters

PathName
Optional. String expression that specifies a file name, directory or folder name, or drive volume label. A zero-length string ("") is returned if PathName is not found.
Attributes
Optional. Enumeration or numeric expression whose value specifies file attributes. If omitted, Dir returns files that match PathName but have no attributes.

Settings

The Attributes argument enumeration values are as follows:

Value	Constant	Description
Normal	vbnormal	Default. Specifies files with no attributes.
ReadOnly	vbReadOnly	Specifies read-only files, in addition to files with no attributes.
Hidden	vbHidden	Specifies hidden files, in addition to files with no attributes.
System	vbSystem	Specifies system files, in addition to files with no attributes.
Volume	vbVolume	Specifies volume label; if any other attribute is specified, vbVolume is ignored.
Directory	vbDirectory	Specifies directories or folders, in addition to files with no attributes.
Archive	vbArchive	File has changed since last backup.
Alias	vbAlias	File has a different name.

Note

These enumerations are specified by the Visual Basic language and can be used anywhere in your code in place of the actual values.

Remarks

The Dir function supports the use of multiple-character (*) and single-character (?) wildcards to specify multiple files.

VbVolume returns the volume label for the drive instead of a specific file name.

You must supply a PathName the first time you call the Dir function. To retrieve the next item, you can make subsequent calls to the Dir function with no parameters.

Security Note:
To run correctly, the Dir function requires the Read and PathDiscovery flags of FileIOPermission to be granted to the executing code. For more information, see FileIOPermission, SecurityException, and Code Access Permissions.

Example

This example uses the Dir function to check if certain files and directories exist.

Dim MyFile, MyPath, MyName As String 
' Returns "WIN.INI" if it exists.
MyFile = Dir("C:\WINDOWS\WIN.INI")   

' Returns filename with specified extension. If more than one *.INI 
' file exists, the first file found is returned.
MyFile = Dir("C:\WINDOWS\*.INI")

' Call Dir again without arguments to return the next *.INI file in the 
' same directory.
MyFile = Dir()

' Return first *.TXT file, including files with a set hidden attribute.
MyFile = Dir("*.TXT", vbHidden)

' Display the names in C:\ that represent directories.
MyPath = "c:\"   ' Set the path.
MyName = Dir(MyPath, vbDirectory)   ' Retrieve the first entry.
Do While MyName <> ""   ' Start the loop.
      ' Use bitwise comparison to make sure MyName is a directory. 
      If (GetAttr(MyPath & MyName) And vbDirectory) = vbDirectory Then 
         ' Display entry only if it's a directory.
         MsgBox(MyName)
      End If   
   MyName = Dir()   ' Get next entry.
Loop

Smart Device Developer Notes

This function is not supported.

Requirements

Namespace:Microsoft.VisualBasic

**Module:**FileSystem

Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)

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