Environ Function

Artikel
11/16/2012

Returns the string associated with an operating-system environment variable.

Overloads Function Environ(ByVal Expression As Integer) As String
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Overloads Function Environ(ByVal Expression As String) As String

Parameters

Expression
Required. Expression that evaluates either a string containing the name of an environment variable, or an integer corresponding to the numeric order of an environment string in the environment-string table.

Exceptions

Exception type	Error number	Condition
ArgumentException	5	Expression is missing.

See the "Error number" column if you are upgrading Visual Basic 6.0 applications that use unstructured error handling. (You can compare the error number against the Number Property (Err Object).) However, when possible, you should consider replacing such error control with Structured Exception Handling Overview for Visual Basic.

Remarks

If Expression contains a string, the Environ function returns the text assigned to the specified environment string—that is, the text following the equal sign (=) in the environment-string table for that environment variable. If the string in Expression cannot be found in the environment-string table, a zero-length string ("") is returned.

If Expression contains an integer, the string occupying that numeric position in the environment-string table is returned. In this case, Environ returns all of the text, including the name of the environment variable. If there is no environment string in the specified position, Environ returns a zero-length string.

Security Note:
The Environ function requires environment permission, which might affect its execution in partial-trust situations. For more information, see SecurityPermission and Code Access Permissions.

Example

This example uses the Environ function to supply the entry number and length of the PATH statement from the environment-string table.

Sub tenv()
   Dim envString As String 
   Dim found As Boolean = False 
   Dim index As Integer = 1
   Dim pathLength As Integer 
   Dim message As String

   envString = Environ(index)
   While Not found And (envString <> "")
      If (envString.Substring(0, 5) = "Path=") Then
         found = True 
      Else
         index += 1
         envString = Environ(index) 
      End If 
   End While 

   If found Then
      pathLength = Environ("PATH").Length
      message = "PATH entry = " & index & " and length = " & pathLength
   Else
      message = "No PATH environment variable exists." 
   End If

   MsgBox(message)
End Sub

Smart Device Developer Notes

This function is not supported.

Requirements

Namespace: Microsoft.VisualBasic

**Module:**Interaction

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

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