Ssh to validate multiple remote hosts connection validation.

Shell Programming and Scripting
1

Dear Folks,

I am trying to read a config file contains ip and port numbers.
i want to read each line of the config file and check ssh connection is happening or not.

Kindly guide.

Config file:

abc@1.2.342        22
abc@1.2.343        22
abc@1.2.344        22
abc@1.2.345        22
abc@1.2.3.116       22
abc@1.2.3.117       22
abc@1.2.3.118       22
abc@1.2.3.119       22
abc@1.2.342        2222
abc@1.2.343        2222
abc@1.2.344        2222
abc@1.2.345        2222
abc@1.2.3.116       2222
abc@1.2.3.117       2222
abc@1.2.3.118       2222
abc@1.2.3.119       2222

#!/bin/sh
while read -r lines || [[ -n $lines ]] ;
do
        hosts=`echo $lines | awk '{print $1}'`
        port=`echo $lines | awk '{print $2}'`
        ssh -q -o "BatchMode=yes" -p $port $hosts "echo 2>&1"
        [ $? -eq 0 ] && echo "Connected to ${hosts} for port ${port}" || echo "Connection refused to ${hosts} for port ${port}, Please check"
done < /home/ssh_configfile

Kindly help, it is checking only for one ip, rest is not passing as an argument.
Regards,
sadique

2

What happens if you try the following script instead?

#!/bin/sh
set -xv
while read -r hosts port
do
        ssh -q -o "BatchMode=yes" -p "$port" "$hosts" "echo 2>&1"
        [ $? -eq 0 ] && echo "Connected to ${hosts} for port ${port}" || echo "Connection refused to ${hosts} for port ${port}, Please check"
done < /home/ssh_configfile
1 Like
3

For half of your configuration entries you don't need the ssh test as they don't comply to the "dotted quad" notation. And, as already implied by Don Cragun's proposal, the || [[ -n $lines ]] is not necessary because it would be executed only if the read failed anyhow (e.g. at enf of file), terminating the while loop.

1 Like
4

It is not working,
not reading all the ips and ports.
Kindly guide.

5

What is not working?
We need the output to understand...
also Looking at don's code I cant believe it failed reading a line, to convince yourself, add a counter in the loop as you know what is expected based on the config file given in input

6

Show us the exact output my script did produce (in CODE tags).

I turned on tracing in that script so we can see what is going on.

If you're not willing to show us the output it produced, there is no reason for us to keep this thread open.

7

Anything special about the input file? Post a hexdump of a small but representative part of it.

1 Like
8

Hmmm - we overlooked the obvious - the first ssh is eating up the rest of the input file. Try adding the -n option...

1 Like
9

Here is the output.

while read -r hosts port
do
        ssh -q -o "BatchMode=yes" -p "$port" "$hosts" "echo 2>&1"
        [ $? -eq 0 ] && echo "Connected to ${hosts} for port ${port}" || echo "Connection refused to ${hosts} for port ${port}, Please check"
done < /home/ssh_configfile
+ read -r hosts port
+ ssh -q -o BatchMode=yes -p 22 abc@1.2.3.42 'echo 2>&1'

+ '[' 0 -eq 0 ']'
+ echo 'Connected to abc@1.2.3.42 for port 22'
Connected to abc@1.2.3.42 for port 22
+ read -r hosts port

i have multiple server and its reading only 1st ip for rest it is not reading and checking the connection.

If anyone who can be humble and kind enough to guide me on the right direction.

Regards,
Sadique

---------- Post updated at 06:06 AM ---------- Previous update was at 06:01 AM ----------

Thanks Rudic your observation worked for me now with my original code i am able to connect to all the ip with their host and validate the connection.
Also as u suggested i have removed the

|| [[ -n $lines ]] ;

Thank you for the help everyone.

10

It would seem that the ssh inside your loop may be consuming all the other input lines.

Perhaps a small adjustment like this might help:-

exec 99</home/ssh_configfile

while read -u 99 -r host port
do
        ssh -q -o "BatchMode=yes" -p "$port" "$hosts" "echo 2>&1"
        [ $? -eq 0 ] && echo "Connected to ${hosts} for port ${port}" || echo "Connection refused to ${hosts} for port ${port}, Please check"
done

Does that help? It is forcing the loop to read from a nominated file descriptor leaving ssh to read STDIN if it wishes.

Can you show us the output (with a set -x before this bit) if it is still stuck? Perhaps just a two line input file would suffice to keep the output small.

Regards,
Robin