Where is my pasted input going?

Question

I am copying and pasting sequences of shell commands into my terminal emulator, and I am confused by the behaviour.

• When I paste the single line ssh user@remote "echo foo"; echo baz the computer does what I expect. It runs the SSH command and then echoes something after I have finished my SSH session.
• When I paste the same thing as a multiple-line command, however, this does not happen.

  ssh user@remote "echo foo"
  echo baz

  I still get the SSH session, but the echo baz completely disappears. No command is run.
• This seems to be something to do with SSH, at least. Because replacing SSH with something else yields the behaviour that I was actually expecting. Both commands run when I paste this, for example:

  echo foo
  echo baz

So what is happening? Where is the pasted input going? Why is the echo command not executed by anything? How is this related to SSH?

(By the way: I know of Ctrl+X, Ctrl+E method, but sometimes, especially when using terminal emulators on Windows, this won't work out of the box.)

Answer 1

Try pasting this:

ssh user@host 'read foo; echo ">>$foo<<"'
echo bar

You will see >>echo bar<< as output from the echo on the server.

This means that ssh will eat the pasted data on its standard input, as if you had done

echo 'echo bar' | ssh user@host 'read foo; echo ">>$foo<<"'

The solution to this, apart from never pasting shell commands into the terminal to run them, is to use ssh -n, which will redirect /dev/null into ssh:

ssh -n user@host 'echo foo'
echo bar

---

Unfortunately I don't know the mechanics of pasting, so I can't say anything clever about why the pasted data ends up on the standard input stream of ssh, but I'm guessing it has to do with the stream being inherited from the interactive shell (which reads commands from standard input).

---

Using ssh -n is also the solution (or at least a solution) to the issue of

while read something; do
    ssh user@host 'somecommand'
done <inputfile

Here, the loop will only run once since ssh eats the data from inputfile.