PowerShell

Read Bytes from a Remote SFTP File (BinData)

Demonstrates the Chilkat SFtp.ReadFileBd method, which reads up to a number of bytes from the current position of an open handle and appends them to a BinData. The arguments are the handle, the maximum number of bytes, and the BinData. This example reads in chunks until end-of-file.

Background: For binary files, reading into a BinData preserves the bytes exactly, unlike a text read that decodes through a charset. Because it appends, the chunked read loop accumulates the whole file in the BinData; each pass reads up to the chunk size and the loop repeats until Eof. Fewer bytes than requested can come back near the end of the file, which is normal.

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Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

$success = $false

#  Demonstrates the SFtp.ReadFileBd method, which reads up to a number of bytes from the current
#  position of an open handle and appends them to a BinData.  The 1st argument is the handle, the
#  2nd is the maximum number of bytes, and the 3rd is the BinData.

$sftp = New-Object Chilkat.SFtp

#  Connect, authenticate, and initialize the SFTP subsystem.
$port = 22
$success = $sftp.Connect("sftp.example.com",$port)
if ($success -eq $false) {
    $($sftp.LastErrorText)
    exit
}

#  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 -eq $false) {
    $($sftp.LastErrorText)
    exit
}

$success = $sftp.InitializeSftp()
if ($success -eq $false) {
    $($sftp.LastErrorText)
    exit
}

$handle = $sftp.OpenFile("subdir/image.png","readOnly","openExisting")
if ($sftp.LastMethodSuccess -eq $false) {
    $($sftp.LastErrorText)
    exit
}

#  Read the file in chunks until end-of-file, accumulating the bytes in a BinData.
$bd = New-Object Chilkat.BinData
$chunkSize = 8192
$reading = $true
while ($reading) {
    $success = $sftp.ReadFileBd($handle,$chunkSize,$bd)
    if ($sftp.LastReadFailed($handle)) {
        $($sftp.LastErrorText)
        exit
    }

    $reading = !$sftp.Eof($handle)
}

$success = $sftp.CloseHandle($handle)
if ($success -eq $false) {
    $($sftp.LastErrorText)
    exit
}

$("Read " + $bd.NumBytes + " bytes.")

$sftp.Disconnect()