Shell Programming and Scripting

#!/bin/bash

MON="SSH"

x=1
while [ "$MON" == "SSH" ]
do
  echo "SSH Checking Status"
  nc 192.168.1.20 -w 2
done

while true
do
        # if exit code not 0 then next cmd also. break = end the while loop
        nc 192.168.1.20 -w 2 >/dev/null 2>&1  || break
        
done

ok=1
while ((ok==1))
do
        # test cmd exist status
        if nc 192.168.1.20 -w 2 >/dev/null 2>&1 
        then 
             # still ok
             ok=1
        else
             ok=0
        fi
done

ok=1
while ((ok==1))
do
        nc 192.168.1.20 -w 2 >/dev/null 2>&1 
        # save last cmd exit status
        stat=$?
        # and test it
        if ((stat==0))
        then 
             # still ok
             ok=1
        else
             ok=0
        fi
done

ok=1
while ((ok==1))
do
        output=$( nc 192.168.1.20 -w 2 2>/dev/null )  # err msg redirect to the /dev/null
        stat=$?
        # stat=0 =ok, other values not ok
        case "$output" in
              "") # empty
                  ok=1
                  ;;
              XXX*) ok=1 ;;
              *) ok=0 ;;
        fi
done