# SFTP Client with Paramiko

This guide demonstrates how to transfer files securely using **SFTP** (SSH File Transfer Protocol). Unlike standard FTP, SFTP encrypts both commands and data. This script uses the `paramiko` library, which is the standard for SSH/SFTP in Python.

**Modules Used:**
*   `paramiko`: Implementation of the SSHv2 protocol.
*   [[programming/python/modules/argparse-module|argparse]]: To handle command-line arguments.

## Installation

```bash
pip install paramiko
```

## The Code

Save this as `sftp_tool.py`.

```python
import paramiko
import argparse
import os
import sys

def sftp_transfer(host, user, password, local_path, remote_path, action):
    # 1. Initialize SSH Transport
    try:
        print(f"Connecting to {host}...")
        transport = paramiko.Transport((host, 22))
        transport.connect(username=user, password=password)
        
        # 2. Create SFTP Client
        sftp = paramiko.SFTPClient.from_transport(transport)
        print("Connection established.")

        # 3. Perform Action
        if action == "upload":
            if not os.path.exists(local_path):
                print(f"Error: Local file '{local_path}' not found.")
                return
            
            print(f"Uploading {local_path} -> {remote_path}...")
            sftp.put(local_path, remote_path)
            print("Upload complete.")
            
        elif action == "download":
            print(f"Downloading {remote_path} -> {local_path}...")
            try:
                sftp.get(remote_path, local_path)
                print("Download complete.")
            except FileNotFoundError:
                print(f"Error: Remote file '{remote_path}' not found.")

        # 4. Close Connection
        sftp.close()
        transport.close()

    except paramiko.AuthenticationException:
        print("Authentication failed. Check credentials.")
    except Exception as e:
        print(f"Error: {e}")

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="SFTP File Transfer Tool")
    parser.add_argument("host", help="SFTP Server Address")
    parser.add_argument("user", help="Username")
    parser.add_argument("password", help="Password")
    parser.add_argument("action", choices=["upload", "download"], help="Action to perform")
    parser.add_argument("local", help="Local file path")
    parser.add_argument("remote", help="Remote file path")
    
    args = parser.parse_args()
    
    sftp_transfer(args.host, args.user, args.password, args.local, args.remote, args.action)
```

## Usage

```bash
# Upload a file
python sftp_tool.py example.com myuser mypass upload ./index.html /var/www/html/index.html

# Download a log file
python sftp_tool.py example.com myuser mypass download ./error.log /var/log/apache2/error.log
```

[[programming/python/python]]