I am trying to pipe commands to an opened SSH session. The commands will be generated by a script, analyzing the results, and sending the next commands in accordance.
I do not want to put all the commands in a script on the remote host, and just run that script, because I am interested also in the status of the SSH process: sending locally the commands allow to "test" whether the SSH connection is alive or not, and get the appropriate return code from the SSH process.
I tried using something along these lines:
$ mkfifo /tpm/commands
$ ssh -t remote </tmp/commands
And from another term:
$ echo "command" >> /tmp/commands
Problem: SSH tells me that no pseudo-tty will be opened for stdin, and closes the connection as soon as "command" terminates.
I tried another approach:
$ ssh -t remote <<EOF
$(echo "command"; while true; do sleep 10; echo "command"; done)
EOF
But then, nothing is flushed to ssh until EOF is reached (in my case, never).
Do any of you have a solution ?
Stop closing /tmp/commands before you're done with it. When you close the pipe, ssh stops reading from it.
exec 7> /tmp/commands. # open once
echo foo >&7 # write multiple times
echo bar >&7
exec 7>&- # close once
You can additionally use ssh -tt to force ssh to open a tty on the remote.