Using cURL for FTP and SFTP transfers enables scripted uploads, downloads, and directory listings without interactive clients. Automating file movement in this way supports scheduled jobs, integration with build pipelines, and quick ad‑hoc transfers using a single, consistent command-line tool. Choosing between plain FTP and encrypted SFTP balances convenience and security based on the data and network environment.
The cURL command encodes the protocol, host, and path directly in the URL, such as ftp://ftp.example.net/ or sftp://sftp.example.net/home/user/. Options like --upload-file, --remote-name, and --continue-at control how files move between the local system and the remote server, while --user and key options supply credentials for authentication. The same syntax pattern applies across supported platforms, which keeps usage consistent on Linux, macOS, and Windows terminals.
Plain FTP exposes credentials and data in clear text, so it suits only non-sensitive content on trusted networks, whereas SFTP wraps traffic inside SSH with strong encryption. Firewalls, proxies, and server configuration can affect which protocol and ports are reachable, and large or unstable transfers often benefit from resume support rather than starting again from byte zero. Switching between FTP and SFTP typically involves changing only the URL scheme and authentication flags.
Steps to use cURL with FTP and SFTP:
- Open a terminal session in an environment where cURL can reach the target FTP or SFTP server.
- Upload a file to an FTP directory using basic authentication.
$ curl --upload-file example.txt "ftp://ftp.example.net/" --user user:password % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 100 29 0 0 100 29 0 1241 --:--:-- --:--:-- --:--:-- 1260FTP transfers, including --user credentials and file contents, travel unencrypted and can be intercepted on untrusted networks.
- Download a file from an FTP directory while preserving the remote filename.
$ curl --remote-name "ftp://ftp.example.net/example.txt" --user user:password % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 100 29 100 29 0 0 1202 0 --:--:-- --:--:-- --:--:-- 1208--remote-name stores the file using the server-side name instead of requiring a local filename argument.
- List the contents of an FTP directory to confirm paths before transferring files.
$ curl --silent "ftp://ftp.example.net/" --user user:password -rw-r--r-- 1 1001 1001 29 Jan 10 06:16 example.txt -rw-r--r-- 1 1001 1001 162 Jan 10 06:13 project-2025-12-archive.tar.gz drwx------ 3 1001 1001 4096 Jan 10 06:13 releases -rw-r--r-- 1 1001 1001 524288 Jan 10 05:41 report.tar.gz
Directory listings reveal exact filenames, sizes, and timestamps, which helps avoid typos and accidental overwrites.
- Upload a file securely to an SFTP home directory using password authentication.
$ curl --upload-file example.txt "sftp://sftp.example.net/home/user/example.txt" --user user:password % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 100 29 0 0 100 29 0 287 --:--:-- --:--:-- --:--:-- 290 100 29 0 0 100 29 0 287 --:--:-- --:--:-- --:--:-- 287SFTP uses the same username and password concept as SSH while encrypting both credentials and data in transit.
- Download a file from an SFTP directory using the same URL pattern as FTP.
$ curl --remote-name "sftp://sftp.example.net/home/user/example.txt" --user user:password % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 100 29 100 29 0 0 276 0 --:--:-- --:--:-- --:--:-- 276 100 29 100 29 0 0 276 0 --:--:-- --:--:-- --:--:-- 276Reusing the same flags and layout across FTP and SFTP reduces mistakes when switching protocols.
- List files on an SFTP directory to inspect remote content and confirm transfer locations.
$ curl --silent "sftp://sftp.example.net/home/user/" --user user:password drwx------ 2 root root 4096 Jan 10 06:14 .ssh drwx------ 2 user user 4096 Jan 10 05:51 .cache -rw-r--r-- 1 user user 220 Mar 31 2024 .bash_logout drwxr-xr-x 1 root root 4096 Jan 10 04:44 .. -rw-r--r-- 1 user user 3771 Mar 31 2024 .bashrc -rw-r--r-- 1 user user 29 Jan 10 06:16 example.txt drwxr-x--- 5 user user 4096 Jan 10 06:14 . drwxr-xr-x 3 user user 4096 Jan 10 06:13 public_html -rw-r--r-- 1 user user 162 Jan 10 06:13 project-2025-12-archive.tar.gz -rw-r--r-- 1 user user 807 Mar 31 2024 .profile
Listing the directory after uploads confirms that files landed in the intended path with the expected ownership.
- Create a partial FTP download when preparing to resume a transfer.
$ curl --range 0-262143 --output report.tar.gz "ftp://ftp.example.net/report.tar.gz" --user user:password % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 100 256k 100 256k 0 0 10.7M 0 --:--:-- --:--:-- --:--:-- 10.8MPartial downloads leave a local file that cURL can reuse as the starting point for a resumed transfer.
- Resume a partial FTP download instead of restarting from the beginning when supported by the server.
$ curl --continue-at - --remote-name "ftp://ftp.example.net/report.tar.gz" --user user:password ** Resuming transfer from byte position 262144 % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 100 256k 100 256k 0 0 11.1M 0 --:--:-- --:--:-- --:--:-- 11.3MResuming requires a matching partial local file; mismatched content produces corrupted downloads that often fail checksum or integrity tests.
- Upload a file over SFTP using existing SSH key material instead of a password.
$ curl --upload-file example.txt "sftp://sftp.example.net/home/user/example.txt" --key /root/.ssh/sg_curl --pubkey /root/.ssh/sg_curl.pub --user user: % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 100 29 0 0 100 29 0 361 --:--:-- --:--:-- --:--:-- 362 100 29 0 0 100 29 0 361 --:--:-- --:--:-- --:--:-- 361Key-based authentication keeps passwords out of scripts and reuses the same OpenSSH keys employed for interactive SSH logins.
- Verify successful transfers by listing the remote SFTP directory again and checking for the expected filenames.
$ curl --silent "sftp://sftp.example.net/home/user/" --user user:password drwx------ 2 user user 4096 Jan 10 06:14 .ssh drwx------ 2 user user 4096 Jan 10 05:51 .cache -rw-r--r-- 1 user user 220 Mar 31 2024 .bash_logout drwxr-xr-x 1 root root 4096 Jan 10 04:44 .. -rw-r--r-- 1 user user 3771 Mar 31 2024 .bashrc -rw-r--r-- 1 user user 29 Jan 10 06:16 example.txt drwxr-x--- 5 user user 4096 Jan 10 06:14 . drwxr-xr-x 3 user user 4096 Jan 10 06:13 public_html -rw-r--r-- 1 user user 162 Jan 10 06:13 project-2025-12-archive.tar.gz -rw-r--r-- 1 user user 807 Mar 31 2024 .profile
Reliable success signals include completed progress meters without errors and the presence of transferred files in directory listings with the correct size.
Mohd Shakir Zakaria is a cloud architect with deep roots in software development and open-source advocacy. Certified in AWS, Red Hat, VMware, ITIL, and Linux, he specializes in designing and managing robust cloud and on-premises infrastructures.
