$if [[ "$(sleep 1 | telnet -c <host> <port> 2>&1 | grep '^SSH')" == SSH* ]]; then <command when up>; else <command when down>; fi;

Test remote SSH server status using telnet (no login required)

This command telnet and and looks for a line starting with "SSH" - works for OpenSSH since the SSH banner is something like "SSH-2.0-OpenSSH_6.0p1 Debian-4+deb7u3". Then it triggers an action accordingly. It can be packed as a script file to echo 0/1 indicating the SSH service availability: if [[ "$(sleep 1 | telnet -c <host> <port> 2>&1 | grep '^SSH')" == SSH* ]]; then echo 1; else echo 0; fi; Alternative uses: Trigger an action when server is UP (using &&): [[ "$(sleep 1 | telnet -c <host> <port> 2>&1 | grep '^SSH')" == SSH* ]] && <command when up> Trigger an action when server is DOWN (using ||): [[ "$(sleep 1 | telnet -c <host> <port> 2>&1 | grep '^SSH')" == SSH* ]] || <command when down>

0
By: paulera
2016-02-02 13:06:51

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What Others Think

Might be easier with netcat: echo | nc localhost 22 ; echo $?
pdxdoughnut · 119 weeks and 5 days ago
echo | nc localhost 22 |& egrep -q '^SSH' ; echo $?
pdxdoughnut · 119 weeks and 5 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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