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SSH in clojure. Uses jsch.



The clj-ssh.cli namespace provides some functions for ease of use at the REPL.

(use 'clj-ssh.cli)

Use ssh to execute a command, say ls, on a remote host "my-host",

(ssh "my-host" "ls")
  => {:exit 0 :out "file1\nfile2\n" :err "")

By default this will use the system ssh-agent to obtain your ssh keys, and it uses your current username, but this can be specified:

(ssh "my-host" "ls" :username "remote-user")
  => {:exit 0 :out "file1\nfile2\n" :err "")

Strict host key checking can be turned off:

(default-session-options {:strict-host-key-checking :no})

SFTP is also supported. For example, to copy a local file to a remote host "my-host":

(sftp "my-host" :put "/from/this/path" "to/this/path")

Note that any sftp commands that change the state of the sftp session (such as cd) do not work with the simplified interface, as a new session is created each time.

If your key has a passphrase, you will need to explicitly add your key either to the system's ssh-agent, or to clj-ssh's ssh-agent with the appropriate add-identity call.


The clj-ssh.ssh namespace should be used for SSH from functional code.

(let [agent (ssh-agent {})]
  (let [session (session agent "host-ip" {:strict-host-key-checking :no})]
    (with-connection session
      (let [result (ssh session {:in "echo hello"})]
        (println (result :out)))
      (let [result (ssh session {:cmd "ls"})]
        (println (second result)))))))

The above example shows using :in to pass commands to a shell, and using :cmd to exec a command without a shell. When using :cmd you can still pass a stream or a string to :in to be used as the process' standard input.

By default, the system ssh-agent is used, which means the ssh keys you use at the command line level should automatically be picked up (this should also work with pageant on windows).

You can forward the ssh-agent, which allows you to run ssh based commands on the remote host using the credentials in your local ssh-agent:

(let [agent (ssh-agent {})]
  (let [session (session agent "host-ip" {:strict-host-key-checking :no})]
    (with-connection session
      (let [result (ssh session {:in "ssh somehost ls" :agent-forwarding true})]
        (println (result :out))))))

If you prefer not to use the system ssh-agent, or one is not running on your system, then a local, isolated ssh-agent can be used.

(let [agent (ssh-agent {:use-system-ssh-agent false})]
  (add-identity agent {:private-key-path "/user/name/.ssh/id_rsa"})
  (let [session (session agent "host-ip" {:strict-host-key-checking :no})]
    (with-connection session
      (let [result (ssh session {:in "echo hello"})]
        (println (result :out)))))

SFTP is supported:

(let [agent (ssh-agent {})]
  (let [session (session agent "host-ip" {:strict-host-key-checking :no})]
    (with-connection session
      (let [channel (ssh-sftp session)]
        (with-channel-connection channel
          (sftp channel {} :cd "/remote/path")
          (sftp channel {} :put "/some/file" "filename"))))))

SSH tunneling is also supported:

    (let [agent (ssh-agent {})]
      (let [session (session agent "host-ip" {:strict-host-key-checking :no})]
        (with-connection session
          (with-local-port-forward [session 8080 80]
            (comment do something with port 8080 here)))))

Jump hosts can be used with the jump-session. Once the session is connected, the the-session function can be used to obtain a session that can be used with ssh-exec, etc. The the-session function can be used on a session returned by session, so you can write code that works with both a jump-session session and a single host session.

(let [s (jump-session
         (ssh-agent {})
         [{:hostname "host1" :username "user"
           :strict-host-key-checking :no}
          {:hostname "final-host" :username "user"
           :strict-host-key-checking :no}]
  (with-connection s
    (ssh-exec (the-session s) "ls" "" "" {}))


Annotated source. API.


Q: What does "4: Failure @ com.jcraft.jsch.ChannelSftp.throwStatusError(" during an sftp transfer signify?

A: Probably a disk full, or permission error.

TTY's and background processes

Some useful links about ssh and background processes:

Thanks to Ryan Stradling for these.


Via clojars and Leiningen.

:dependencies [clj-ssh "0.5.14"]

or your favourite maven repository aware tool.


The test rely on several keys being authorized on localhost:

ssh-keygen -f ~/.ssh/clj_ssh -t rsa -C "key for test clj-ssh" -N ""
ssh-keygen -f ~/.ssh/clj_ssh_pp -t rsa -C "key for test clj-ssh" -N "clj-ssh"
cp ~/.ssh/authorized_keys ~/.ssh/authorized_keys.bak
echo "from=\"localhost\" $(cat ~/.ssh/" >> ~/.ssh/authorized_keys
echo "from=\"localhost\" $(cat ~/.ssh/" >> ~/.ssh/authorized_keys

The clj_ssh_pp key should have a passphrase, and should be registered with your ssh-agent.

ssh-add ~/.ssh/clj_ssh_pp

On OS X, use:

ssh-add -K ~/.ssh/clj_ssh_pp

Other Libraries

For plain ftp, you might want to look at clj-ftp.


Copyright © 2012 Hugo Duncan

Licensed under EPL

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Hugo Duncan, Neale Swinnerton & David Barker
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