Check whether ssh is possible inside shell a script?

Question

I need to print a count of a remote server which is written on '/REMOTE_DIR/DR_count'. But that remote server is not much reliable due to a network or OS failure. However I need to print the DR_count value from the local machine if that remote machine is not available. Here is my logic. Please correct me to how to check that if condition in correct way. I'm running this script on Solaris 11.3.

#!/bin/sh

if[check wether ssh user@host_name is possible]
then 

op="cat /REMOTE_DIR/DR_count"
cmd="ssh user@host_name $op"
drlog=`$cmd`

else 

drlog='cat /LOCAL_DIR/DR_count'


fi


echo $drlog

Why don't you simply try to ssh to the host and check the exit code of the command, to see whether your were successful? — user1934428
– user1934428, Commented Nov 22, 2019 at 7:08

Nwn · Accepted Answer · 2019-11-22 11:48:47Z

3

As I said in my comment, I would simply try to ssh, and if use its exit code to see whether it worked:

ssh -o ConnectTimeout=5 user@host_name cat /REMOTE_DIR/DR_count 2>/dev/null || cat /LOCAL_DIR/DR_count

edited Nov 22, 2019 at 11:48

Nwn

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answered Nov 22, 2019 at 7:25

user1934428

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Comments

Maxim Sagaydachny · Accepted Answer · 2019-11-22 07:28:40Z

1

you should check for exit code 255 to detect whether you have network error or not

#!/bin/bash

#EXIT STATUS
#     ssh exits with the exit status of the remote command or with 255 if an error occurred.

cnt=`ssh -o ConnectTimeout=5 root@$host "cat /REMOTE_DIR/DR_count"`

exit_code=$?

if [ $exit_code -eq 255 ]; then
    cnt=`cat /LOCAL_DIR/DR_count`
fi

it makes sense also to check for other (non 0 / 255) exit codes to check possible issues at remote side (like file missing on remote side)

answered Nov 22, 2019 at 7:28

Maxim Sagaydachny

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