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How to Resume File Transferring With Paramiko?

6 minutes read

To resume file transferring with Paramiko, you can use the file_seek method to seek to the position in the file where the transfer was interrupted. This method allows you to set the position in the file from which the next read or write operation will begin. By storing the current position in the file before the interruption and then using file_seek to jump back to that position, you can resume the file transfer from where it left off. This can be useful for large file transfers or transfers that may be interrupted for any reason. By properly handling the file position and using the file_seek method, you can ensure that your file transfer resumes successfully without having to start over from the beginning.


What is the recommended way to resume file transfer with paramiko?

In order to resume a file transfer with Paramiko, you can use the SFTPClient.open() method with the a (append) mode instead of w (write) mode. This will allow you to open the file for writing and continue transferring data from the current position in the file.


Here is an example code snippet demonstrating how to resume file transfer with Paramiko:

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import paramiko

# Establish an SSH connection
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect('hostname', username='username', password='password')

# Open a SFTP connection
sftp = ssh.open_sftp()

# Remote file path
remote_path = '/path/to/remote/file'

# Local file path
local_path = '/path/to/local/file'

# Open the remote file in append mode
remote_file = sftp.open(remote_path, 'ab')

# Open the local file in read mode
local_file = open(local_path, 'rb')

# Read data from the local file and write it to the remote file
data = local_file.read(1024)
while data:
    remote_file.write(data)
    data = local_file.read(1024)

# Close the files and the SFTP connection
local_file.close()
remote_file.close()
sftp.close()
ssh.close()


By opening the remote file in append mode and reading the local file from the current position, you can resume transferring the file from where the previous transfer was interrupted.


How to resume a file transfer with paramiko using a different connection?

To resume a file transfer with paramiko using a different connection, you can follow these steps:

  1. Open a new SSH connection using paramiko with the desired connection details.
  2. Use the SFTPClient.from_transport() method to create a new SFTPClient object using the new SSH connection.
  3. Use the SFTPClient.file method to open the file on the remote server that you want to resume the transfer for.
  4. Use the SFTPClient.getfo() method to resume the file transfer, specifying the local file object to write to and the offset to resume from.


Here is an example code snippet to demonstrate how to resume a file transfer with paramiko using a different connection:

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import paramiko

# Create a new SSH client
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())

# Connect to the remote server with the new connection details
client.connect('hostname', username='username', password='password')

# Create a new SFTP client using the new SSH connection
sftp = client.open_sftp()

# Open the remote file that you want to resume the transfer for
remote_file = sftp.file('/path/to/remote/file', 'rb')

# Specify the local file object to write to and the offset to resume from
local_file = open('/path/to/local/file', 'ab')
offset = local_file.tell()
remote_file.seek(offset)

# Resume the file transfer
sftp.getfo('/path/to/remote/file', local_file, offset)

# Close the connections and files
remote_file.close()
local_file.close()
sftp.close()
client.close()


In this code snippet, we open a new SSH connection to the remote server with the desired connection details, create a new SFTP client using the new SSH connection, and resume the file transfer for the specified file using the getfo() method. Remember to close all connections and files properly after the file transfer is complete.


How to handle errors while transferring files with paramiko?

When transferring files with paramiko, you can handle errors in the following ways:

  1. Catch exceptions: Use try-except blocks to catch exceptions that may occur during file transfer. Paramiko provides specific exceptions for different errors that may occur, such as FileNotFoundError, SSHException, IOError, etc. You can catch these exceptions and handle them accordingly.
  2. Check for errors: Before initiating the file transfer, you can check for errors such as file not found, permission denied, connection error, etc. This can help prevent errors from occurring during the transfer process.
  3. Log errors: It is a good practice to log errors that occur during file transfer. This can help in troubleshooting and debugging issues later on. You can use the logging module in Python to log errors to a file or console.
  4. Retry mechanism: If an error occurs during file transfer, you can implement a retry mechanism to attempt the transfer again. You can set a maximum number of retries and implement backoff strategies to reduce the chances of errors occurring again.
  5. Graceful handling: Handle errors gracefully by providing informative error messages to the user and taking appropriate actions, such as closing the connection, cleaning up temporary files, etc.


By following these best practices, you can effectively handle errors while transferring files with paramiko and ensure a smooth and reliable transfer process.


How to resume a file transfer with paramiko if the destination file already exists?

If you are using Paramiko to transfer a file and the destination file already exists, you can check the size of the destination file and resume the transfer from where it left off. Here is an example code snippet demonstrating how to resume a file transfer using Paramiko:

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import paramiko

def resume_transfer(source_file, destination_file, hostname, username, password):
    transport = paramiko.Transport((hostname, 22))
    transport.connect(username=username, password=password)
    sftp = paramiko.SFTPClient.from_transport(transport)

    # Get the size of the destination file
    try:
        existing_size = sftp.stat(destination_file).st_size
    except FileNotFoundError:
        existing_size = 0

    # Open the source file and seek to the existing size
    with open(source_file, 'rb') as f:
        f.seek(existing_size)
        
        # Open the destination file in append mode for resuming the transfer
        with sftp.file(destination_file, 'ab') as dest_file:
            # Transfer the file from the seek position
            dest_file.set_pipelined(True)
            for line in f:
                dest_file.write(line)

    sftp.close()
    transport.close()

source_file = 'source_file.txt'
destination_file = 'destination_file.txt'
hostname = 'your_hostname'
username = 'your_username'
password = 'your_password'

resume_transfer(source_file, destination_file, hostname, username, password)


This code snippet will resume the transfer of the source file to the destination file starting from the existing size of the destination file. It reads the source file from the existing size and appends the content to the destination file. Make sure to replace the placeholder values in the code with your actual information.


How to use paramiko to transfer large files efficiently?

To transfer large files efficiently using Paramiko, you can use the SFTPClient class provided by Paramiko. Here is an example code snippet that demonstrates how to transfer a large file using Paramiko:

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import paramiko

# Establish an SSH connection to the remote server
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect('remote_host', username='username', password='password')

# Create an SFTP client object
sftp = ssh.open_sftp()

# Define the local and remote file paths
local_path = 'local_file_path'
remote_path = 'remote_file_path'

# Open the local file for reading
with open(local_path, 'rb') as local_file:
    # Create the remote file for writing
    sftp_file = sftp.file(remote_path, 'wb')

    # Transfer the contents of the local file to the remote file
    sftp_file.write(local_file.read())

    # Close the remote file
    sftp_file.close()

# Close the SFTP client and SSH connection
sftp.close()
ssh.close()


In this example, the open method is used to open the local file for reading, and the file method is used to create the remote file for writing. The contents of the local file are then read and transferred to the remote file using the write method.


By using Paramiko's SFTP client, you can efficiently transfer large files over an SSH connection.

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