VBScript

Read Text at a 32-bit Offset from a Remote SFTP File

Demonstrates the Chilkat SFtp.ReadFileText32 method, which reads up to a number of bytes from a specific 32-bit byte offset of an open handle and decodes them to text. The arguments are the handle, the offset, the maximum number of bytes, and the charset.

Background: Reading from an explicit offset lets you fetch just the part of a file you need — a header, a record at a known position, a slice of a large log — without downloading everything before it. As with offset writes, the offset counts bytes rather than characters, so it must respect the encoded width of any multibyte content.

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Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

'  Demonstrates the SFtp.ReadFileText32 method, which reads up to a number of bytes from a
'  specific 32-bit byte offset of an open handle and decodes them to text.  The 1st argument is
'  the handle, the 2nd is the offset, the 3rd is the maximum number of bytes, and the 4th is the
'  charset.

set sftp = CreateObject("Chilkat.SFtp")

'  Connect, authenticate, and initialize the SFTP subsystem.
port = 22
success = sftp.Connect("sftp.example.com",port)
If (success = 0) Then
    outFile.WriteLine(sftp.LastErrorText)
    WScript.Quit
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.
password = "mySshPassword"

success = sftp.AuthenticatePw("mySshLogin",password)
If (success = 0) Then
    outFile.WriteLine(sftp.LastErrorText)
    WScript.Quit
End If

success = sftp.InitializeSftp()
If (success = 0) Then
    outFile.WriteLine(sftp.LastErrorText)
    WScript.Quit
End If

handle = sftp.OpenFile("subdir/record.dat","readOnly","openExisting")
If (sftp.LastMethodSuccess = 0) Then
    outFile.WriteLine(sftp.LastErrorText)
    WScript.Quit
End If

'  Read 5 bytes starting at byte offset 10, without first reading the bytes before it.
offset = 10
numBytes = 5
text = sftp.ReadFileText32(handle,offset,numBytes,"utf-8")
If (sftp.LastMethodSuccess = 0) Then
    outFile.WriteLine(sftp.LastErrorText)
    WScript.Quit
End If

outFile.WriteLine(text)

success = sftp.CloseHandle(handle)
If (success = 0) Then
    outFile.WriteLine(sftp.LastErrorText)
    WScript.Quit
End If

sftp.Disconnect 

outFile.Close