ftp

Overview

The ftp command is a file transfer protocol client used to transfer files between local and remote systems. While largely superseded by more secure alternatives, it’s still used for legacy systems and public file servers.

Syntax

ftp [options] [host]

Common Options

Option Description
-4 Use IPv4 only
-6 Use IPv6 only
-A Force active mode
-a Use anonymous login
-d Enable debugging
-e Disable command editing
-g Disable filename globbing
-i Turn off interactive prompting
-n No auto-login
-p Use passive mode
-v Verbose output

Key Use Cases

  1. File transfer to/from FTP servers
  2. Legacy system integration
  3. Public file downloads
  4. Automated file transfers
  5. System administration

Examples with Explanations

Example 1: Connect to FTP Server

ftp ftp.example.com

Connects to FTP server and prompts for credentials

Example 2: Anonymous FTP

ftp -a ftp.example.com

Connects using anonymous login

Example 3: Non-interactive Mode

ftp -n ftp.example.com

Connects without automatic login

FTP Commands

Command Description
ls List remote files
cd Change remote directory
lcd Change local directory
pwd Show remote directory
lpwd Show local directory
get Download file
put Upload file
mget Download multiple files
mput Upload multiple files
binary Set binary transfer mode
ascii Set ASCII transfer mode
passive Toggle passive mode
quit Exit FTP

File Transfer Examples

Download Files

ftp> get filename.txt
ftp> mget *.txt
ftp> get remote.txt local.txt

Upload Files

ftp> put filename.txt
ftp> mput *.txt
ftp> put local.txt remote.txt

Transfer Modes

Mode Description
ASCII Text files (default)
Binary Binary files
Auto Automatic detection

Set transfer mode:

ftp> binary
ftp> ascii

Common Usage Patterns

  1. Batch download:

    ftp> mget *.log

  2. Directory synchronization:

    ftp> lcd /local/path
ftp> cd /remote/path
ftp> mget *

  3. Automated transfer:

    ftp> prompt off
ftp> mput *.txt

Passive vs Active Mode

  • Active Mode: Server connects back to client
  • Passive Mode: Client connects to server for data

Enable passive mode:

ftp> passive

Scripting FTP Operations

  1. Using here document:

    ftp -n ftp.example.com << EOF
user username password
binary
cd /remote/path
lcd /local/path
mget *.txt
quit
EOF

  2. Using command file:

    echo "user username password
binary
get file.txt
quit" > ftp_commands.txt
ftp -n ftp.example.com < ftp_commands.txt

Security Considerations

  1. Unencrypted protocol
  2. Credentials sent in plain text
  3. Data transmitted unencrypted
  4. Use SFTP/SCP for secure transfers
  5. Firewall configuration needed

Best Practices

  1. Use secure alternatives when possible
  2. Use passive mode for firewalls
  3. Set appropriate transfer modes
  4. Verify file transfers
  5. Use automation for repetitive tasks

Automated FTP Scripts

  1. Backup script:

    #!/bin/bash
HOST="backup.server.com"
USER="backup_user"
PASS="backup_pass"

ftp -n $HOST << EOF
user $USER $PASS
binary
cd /backups
lcd /local/backups
mput *.tar.gz
quit
EOF

  2. Download script:

    #!/bin/bash
ftp -n ftp.example.com << EOF
user anonymous anonymous@domain.com
binary
cd /pub/files
mget *.zip
quit
EOF

Error Handling

  1. Connection errors:

    ftp -v ftp.server.com 2>&1 | grep -i error

  2. Transfer verification:

    ftp> hash  # Show progress
ftp> status  # Show connection status

Performance Optimization

  1. Use binary mode for non-text files
  2. Enable hash marks for progress
  3. Use passive mode for better connectivity
  4. Consider parallel transfers for multiple files

Troubleshooting

  1. Connection refused
  2. Login failures
  3. Transfer mode issues
  4. Firewall problems
  5. Permission errors

Modern Alternatives

Instead of FTP, consider: 1. sftp - Secure FTP over SSH 2. scp - Secure copy over SSH 3. rsync - Efficient file synchronization 4. curl - Modern data transfer 5. wget - Web-based downloads

Integration Examples

  1. Log rotation upload:

    # Upload rotated logs
find /var/log -name "*.gz" -mtime -1 | while read file; do
    echo "put $file" | ftp -n backup.server.com
done

  2. Configuration deployment:

    ftp -n config.server.com << EOF
user deploy deploy_pass
ascii
cd /configs
mput *.conf
quit
EOF