VB.NET

Check if a Remote File or Directory Exists

Demonstrates the Chilkat SFtp.FileExists method, which checks a remote path and returns an integer describing what is there. The first argument is the remote path and the second (followLinks) selects whether a symbolic link is followed to its target. The return value is -1 on error, 0 if nothing exists, 1 for a file, 2 for a directory, 3 for a symbolic link, and higher values for special entry types.

Background: This returns more than a yes/no because "does it exist" usually comes with "and is it the kind of thing I expect" — a job that means to write a file should notice if a directory already occupies the path. The followLinks flag decides whether a symbolic link is reported as a link (3, only when not following) or transparently resolved to its target's type. Always handle the -1 case: it means the check itself failed, which is different from the path not existing.

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Dim success As Boolean = False

'  Demonstrates the SFtp.FileExists method, which checks a remote path and returns an integer
'  describing what is there.  The 1st argument is the remote path and the 2nd (followLinks)
'  selects whether a symbolic link is followed to its target.

Dim sftp As New Chilkat.SFtp

'  Connect, authenticate, and initialize the SFTP subsystem.
Dim port As Integer = 22
success = sftp.Connect("sftp.example.com",port)
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


'  Normally you would not hard-code the password in source.  You should instead obtain it
'  from an interactive prompt, environment variable, or a secrets vault.
Dim password As String = "mySshPassword"

success = sftp.AuthenticatePw("mySshLogin",password)
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


success = sftp.InitializeSftp()
If (success = False) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


'  When followLinks is True, a symbolic link is followed and the target's type is returned.
Dim followLinks As Boolean = True
Dim result As Integer = sftp.FileExists("subdir/report.pdf",followLinks)

'  Interpret the return value.
If (result = -1) Then
    Debug.WriteLine(sftp.LastErrorText)
    Exit Sub
End If


If (result = 0) Then
    Debug.WriteLine("The path does not exist.")
End If


If (result = 1) Then
    Debug.WriteLine("A regular file exists.")
End If


If (result = 2) Then
    Debug.WriteLine("A directory exists.")
End If


'  Other possible values: 3 = symbolic link (only when followLinks is False), 4 = special
'  entry, 5 = unknown, 6 = socket, 7 = character device, 8 = block device, 9 = FIFO.

sftp.Disconnect()