Perl

Check Whether the Last SFTP Read Failed

Demonstrates the Chilkat SFtp.LastReadFailed method, which returns whether the most recent read for a handle failed. The only argument is the handle. A normal end-of-file is not a failure.

Background: A chunked read loop needs to tell three outcomes apart: more data, a clean end-of-file, and an actual error such as a dropped connection or a revoked handle. LastReadFailed isolates the error case — it is false on a normal EOF read (which succeeds with zero bytes) and true for an empty, malformed, or already-closed handle — so the loop can stop cleanly on EOF but bail out with an error message on a genuine failure.

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Perl

use chilkat();

$success = 0;

#  Demonstrates the SFtp.LastReadFailed method, which returns whether the most recent read for a
#  handle failed.  The only argument is the handle.  A normal end-of-file is NOT a failure.

$sftp = chilkat::CkSFtp->new();

#  Connect, authenticate, and initialize the SFTP subsystem.
$port = 22;
$success = $sftp->Connect("sftp.example.com",$port);
if ($success == 0) {
    print $sftp->lastErrorText() . "\r\n";
    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 == 0) {
    print $sftp->lastErrorText() . "\r\n";
    exit;
}

$success = $sftp->InitializeSftp();
if ($success == 0) {
    print $sftp->lastErrorText() . "\r\n";
    exit;
}

$handle = $sftp->openFile("subdir/data.txt","readOnly","openExisting");
if ($sftp->get_LastMethodSuccess() == 0) {
    print $sftp->lastErrorText() . "\r\n";
    exit;
}

$reading = 1;
$chunkSize = 4096;
$bd = chilkat::CkBinData->new();
while ($reading) {
    $success = $sftp->ReadFileBd($handle,$chunkSize,$bd);

    #  Distinguish an actual read failure from a normal EOF.  On EOF the read succeeds, returns
    #  zero bytes, and LastReadFailed is 0.
    if ($sftp->LastReadFailed($handle)) {
        print "Read failed: " . $sftp->lastErrorText() . "\r\n";
        exit;
    }

    $reading = !$sftp->Eof($handle);
}

$success = $sftp->CloseHandle($handle);
if ($success == 0) {
    print $sftp->lastErrorText() . "\r\n";
    exit;
}

print "Read " . $bd->get_NumBytes() . " bytes with no read failures." . "\r\n";

$sftp->Disconnect();