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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Chilkat2 Perl

use strict;
use warnings;
use Chilkat2;

# 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.

my $sftp = Chilkat2::SFtp->new;

# Connect, authenticate, and initialize the SFTP subsystem.
my $port = 22;
my $success = $sftp->Connect('sftp.example.com', $port);
if (!$success) {
    print $sftp->LastErrorText, "\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.
my $password = 'mySshPassword';

$success = $sftp->AuthenticatePw('mySshLogin', $password);
if (!$success) {
    print $sftp->LastErrorText, "\n";
    exit;
}

$success = $sftp->InitializeSftp();
if (!$success) {
    print $sftp->LastErrorText, "\n";
    exit;
}

my $handle = $sftp->OpenFile('subdir/data.txt', 'readOnly', 'openExisting');
if (!$sftp->LastMethodSuccess) {
    print $sftp->LastErrorText, "\n";
    exit;
}

my $reading = 1;
my $chunkSize = 4096;
my $bd = Chilkat2::BinData->new;
while ($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, "\n";
        exit;
    }

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

$success = $sftp->CloseHandle($handle);
if (!$success) {
    print $sftp->LastErrorText, "\n";
    exit;
}

print 'Read ', $bd->NumBytes, " bytes with no read failures.\n";

$sftp->Disconnect();