Shell Programming and Scripting

I want to pass the text of a bash shell function to a remote machine in such a way that I can execute that function on the remote machine. For example, I can do this in a script

ssh some_machine "tfunc () { echo Hello from \$(uname -n) ; } ; tfunc ; "

and the function tfunc() will be executed on the remote machine. I'd like to be able to define the function in my current shell and then use that definition in the ssh command, as in

function tfunc { echo Hello from $(uname -n) ; }
ssh some_machine " <tfunc text here> ; tfunc ; "

The set() command (with no arguments) prints all the variables and functions known the shell, but this is too much. I'd like to be able to get just the text of the function I want to pass. Since the set() command knows the function text it seems like it must be available, but I haven't been able to figure out how to do this. Does anyone know if this is possible? Thanks.

Mark E. Hamilton

Yes. It works almost exactly as you've given it, even. All I did was change some_machine to a real hostname.

You don't need to put it in a function, either. Just give it "echo Hello from \$(uname -n)" and it goes.

I don't see a way to make set list only the variables and functions you want. It either lists everything, or sets options, set being what it is. If you know the function is define all on one line like you've done, you can grep for them easily.

It's not really available. You can't export functions.

Why can't you just run the code with ssh?

Like:

Code:

ssh some_machine "\$(uname -n)"

The actual function I want to pass to the remote machine is much more complex. What I posted was just a simplified example of my problem. I want to use the function both in the shell script and on the remote machine, and if I define it in multiple places (once for my shell script to use and once in the ssh call) it becomes much more difficult to maintain; changes to one might not get made in the other.

Also, unfortunately, my function is not a single line, but even when it is set() turns it into multiple lines;

Code:

% function tfunc { echo Hi ; }
% set
...
tfunc ()
{
    echo Hi
}

If you have ssh, why don't you put what you have to run in a script, scp that, and then run it - via ssh?

That's going to get pretty difficult, and could break in lots of interesting ways depending on shell, shell version, shell options, and the robustness of your re-escaping.

Have you considered putting the relevant function in a script file, to share that file with the servers? Your script could sftp it over first, then call it with ssh like

Code:

ssh server_name 'source ./script_file ; function_name'

Or you could just arrange to have the script file sourced in the server's .bashrc or what have you.

[edit] crosspose. scottn beats me again!

Yes, I could put the function in a separate script and scp it to the remote machine, then execute it there. The approach I was asking about would be much simpler, however. Nothing external to the script itself would be required.

FWIW, this example is similar to what I was thinking about:

Code:

% func_str="function tfunc { uname -n ; }"
% eval $func_str
% tfunc
my_machine
%  ssh some_machine "${func_str} ; tfunc ; "
some_machine
%

Thanks.