'環境変数を取得する関数

Option Explicit

Private Declare Function GetEnvironmentVariable Lib "kernel32" Alias "GetEnvironmentVariableA" ( _
    ByVal lpszName As String, ByVal lpszValue As String, _
    ByVal cchValue As Long) As Long

Public Function GetEnv(ByVal sName As String) As String
    Dim lpBuffer As String
    Dim iSize As Long
    Dim iRet As Long
    GetEnv = ""
    lpBuffer = String$(512, Chr$(0))
    iSize = GetEnvironmentVariable(sName, lpBuffer, 512)
    If iSize = 0 Then
    ElseIf iSize <= 512 Then
        GetEnv = Left$(lpBuffer, InStr(1, lpBuffer, Chr$(0), 0) - 1)
    Else
        lpBuffer = String$(iSize, Chr$(0))
        iRet = GetEnvironmentVariable(sName, lpBuffer, iSize)
        If iRet = iSize - 1 Then
            GetEnv = Left$(lpBuffer, InStr(1, lpBuffer, Chr$(0), 0) - 1)
        End If
    End If
End Function


Sub Test()
    MsgBox GetEnv("path")
End Sub