shell script to run commands over SSH on multiple remote servers [duplicate] - linux

Question

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While loop stops reading after the first line in Bash
(5 answers)
Closed 1 year ago.
I need to check if telnet is happening or not on multiple remote servers.
I wrote a while loop to SSH over multiple remote servers and triggers an email whenever the telnet fails. But the issue is while loops iterates only over the first server and exits out of the script without reading remaining servers. Below is my shell script
#!bin/bash
while read host_details
do
USERNAME=$(echo $host_details | awk -F"|" '{print $1}')
HOSTIP=$(echo $host_details | awk -F"|" '{print $2}')
PORT=$(echo $host_details | awk -F"|" '{print $3}')
PROXY=$(echo $host_details | awk -F"|" '{print $4}')
PROXY_PORT=$(echo $host_details | awk -F"|" '{print $5}')
STATUS=$(ssh -n ${USERNAME}#${HOSTIP} -p${PORT} "timeout 4 bash -c \"</dev/tcp/${PROXY}/${PROXY_PORT}\"; echo $?;" < /dev/null)
if [ "$STATUS" -ne 0 ]
then
echo "Connection to $PROXY on port $PROXY_PORT failed"
mutt -s "Telnet connection to $PROXY on port $PROXY_PORT failed" abc.def#xyz.com
else
echo "Connection to $PROXY on port $PROXY_PORT succeeded"
mutt -s "Telnet connection to $PROXY on port $PROXY_PORT succeeded" abc.def#xyz.com
fi
done<.hostdetails
I observed my script works only when I remove IF condition and my while loops iterates over all the servers as expected.
Can anyone suggest why when I use IF condition the script exits after first iteration? And how to make it work and get the email alerts?

Answer 1

Thanks to #GordonDavisson recommendation.
The mutt in the script is treating the remaining server details as an input list, hence the script is getting terminated after reading the first server values.
Replace mutt with another email program in your script.
However, users who wish to go with mutt, then it is recommended to add content to their email body or redirect the stdin from mutt to /dev/null
Below is the working solution:
#!bin/bash
while IFS="|" read -r userName hostIp Port Proxy proxyPort
do
STATUS=$(ssh -n -tt -o LogLevel=quiet ${userName}#${hostIp} -p${Port} 'timeout 4 /bin/bash -c' \'"</dev/tcp/${Proxy}/${proxyPort}"\'; echo $? < /dev/null | tr -d '\r')
if [ "$STATUS" -ne 0 ]
then
echo "Connection to $Proxy on port $proxyPort failed" | mutt -s "${hostIp}:Telnet connection to $Proxy on port $proxyPort failed" abc.def#xyz.com
else
echo "Connection to $Proxy on port $proxyPort succeeded" | mutt -s "${hostIp}:Telnet connection to $Proxy on port $proxyPort succeeded" abc.def#xyz.com
fi
done<.hostdetails
The trim command in the solution is to delete the carriage return(\r) I was getting in the variable(STATUS)