CkPython

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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import sys
import chilkat

success = False

#  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()

#  Connect, authenticate, and initialize the SFTP subsystem.
port = 22
success = sftp.Connect("sftp.example.com",port)
if (success == False):
    print(sftp.lastErrorText())
    sys.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 == False):
    print(sftp.lastErrorText())
    sys.exit()

success = sftp.InitializeSftp()
if (success == False):
    print(sftp.lastErrorText())
    sys.exit()

handle = sftp.openFile("subdir/data.txt","readOnly","openExisting")
if (sftp.get_LastMethodSuccess() == False):
    print(sftp.lastErrorText())
    sys.exit()

reading = True
chunkSize = 4096
bd = chilkat.CkBinData()
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 False.
    if (sftp.LastReadFailed(handle)):
        print("Read failed: " + sftp.lastErrorText())
        sys.exit()

    reading = not sftp.Eof(handle)

success = sftp.CloseHandle(handle)
if (success == False):
    print(sftp.lastErrorText())
    sys.exit()

print("Read " + str(bd.get_NumBytes()) + " bytes with no read failures.")

sftp.Disconnect()