Bash – How to execute a remote alias over an SSH

aliasbashcommand linessh

How do I execute a remote alias over an SSH?

For instance, there is a rather complex alias for rkhunter, and I would like to execute it in one command over ssh like that:

ssh user@server_ip -p port_number -t alias_name_defined_on_server

To be exact, the alias is defined in .bash_aliases which is sourced by .bashrc of this particular user.

Best Answer

A working answer was published in SO, quoted below:

Quoted from the man page of bash: Aliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using shopt ...

So the simplest way IMO is to put the following lines at the top of your /home/<user>/.bashrc file:
# comment out the original line
# [ -z "$PS1" ] && return

if [ -z "$PS1" ]; then
  shopt -s expand_aliases
  # alias ls='ls --color=always'
  # return
fi
Save and exit. Now you can run ssh user@host "your_alias" successfully.

Note: If your ~/.bashrc hold something like the below, comment the line that return when the shell is not interactive:

# If not running interactively, don't do anything
 case $- in
     *i*) ;;
       *) return;;
 esac

Related Solutions

SSH – Using LocalCommand on Exit

It's not specified in the question if you want this executed on the local or remote machine. It's also not specified which shell is present on either machine, so I'm assuming bash for both.

If you want to execute it on the remote machine, look at ~/.bash_logout, which is executed when a login shell logs out gracefully. From man bash:

When a login shell exits, bash reads and executes commands from the file ~/.bash_logout, if it exists.

You can do a test in ~/.bash_logout to check if the shell being logged out of is an SSH session, something like the following should work:

if [[ $SSH_CLIENT || $SSH_CONNECTION || $SSH_TTY ]]; then
    # commands go here
fi

If you want to execute it on the local machine, create a function wrapper around ssh. Something like the following should work:

ssh() {
    if command ssh "$@"; then
        # commands go here
    fi
}

That may be too simple for your needs, but you get the idea.

Ssh: execute a command before login

You are likely looking for the -t option for ssh which forces pseudo-terminal allocation - without that you are just directly connecting your terminal to standard input/output/error of the remotely running programs. Hence your command should look like this:

ssh -t mymachine.example.com 'mount /home ; /bin/bash'

Best Answer

Related Solutions

SSH – Using LocalCommand on Exit

Ssh: execute a command before login

Related Question