UNIX for Beginners Questions & Answers

Attention:
ssh -qn is ssh -q -n where -n inhibits reading from stdin - good for ssh -q -n remotehost remotecommand. But it must be ssh -q remotehost < file and ssh -q remotehost << heredoc and ssh -q remotehost <<< herestring because here you want it to read from stdin.

Also I suspect that in a normal here-document the backtick expression `uname -r`is already locally evaluated, so the local result will be passed to the remote host.
A workaround is <<-"EOFSSH" where the quotes should suppress the immediate evaluation of backtick-expressions and all kinds of $-expressions in the following here-document.

Thanks, MadeInGermany, for pointing that ssh -n option out. Still, the commands are passed as such (no backtics ``!) to the remote server, so uname -r will be executed remotely.


The script was tested successfully as given in post #4, admittedly on one single server only. The respective variables were correctly filled with the remote info. If something does not work as expected, start over and test stepwise:
- log into the respective remote server(s) and interactively run the commands as given. They should give a one line output each. Multiline output will make the approach fail.
- run the entire ssh command on one server and with one remote command, then with multiple commands, reading results into local variables
- test remote access on all servers, with one command, and then with multiple. If one server (the 50th?) fails, repeat former steps on this one. The error may be due to a remote inconsistency.

- include thorough debuggung / error handling between command (blocks).


I quickly verified the code reading multiple remote servers from a SOURCE_FILE, and it works. echo the remote IP before running the ssh command.

Hello RudiC,

I've continued to work on this script using your suggestions and I'm very happy to report that your script suggestion has worked for me. I did as you suggested and tried your code on one VM and I was successful producing the variables in the HERE DOCUMENT with one connection to each server. This should greatly improve the speed and efficiency of my script.

Thanks very much to you and all who contributed to this thread! Very much appreciate your patience in explaining how to make this code work.