bash - Validate an IP before using scp -

i'm writing file transfer script , gets pretty complex. in beginning when generate ip address transfer from, want validate can indeed connect it. code in area looks this:

user_id=$1 if [[ $group == "a" ]];     address="${user_id}@morgan.company.gov" elif [[ $group == "b" ]];     address="${user_id}@mendel.company.gov" else     log_msg fatal "couldn't resolve group $group. exiting"     exit 1; fi  // here want test $address exists, , can connect right // have below.  think there better way  ssh -q $address exit if [ $? != 0 ];     log_msg fatal "couldn't resolve host, have login privileges $address" fi  ... // lots of other things happen  scp $address:$incoming_file $new_file  

what have works, doesn't seem elegant solution. i'd prefer not ssh , exit server, test connection.

you can use shell function tests wether host has ssh port open or not:

#!/bin/bash function isup(){     local ip=$1     local sshport=22     if [[ $ip =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]];         if [[ $(nmap -p0 $ip -p$sshport | grep ^$sshport | cut -d' ' -f2) == "open" ]];             return 0         else             return 1         fi     fi } if isup $1;     ssh $1 uptime else     echo "host $1 not available" fi 

or make use of (new me) bash functionality:

#!/bin/bash function isup(){    local ip=$1    if echo > /dev/tcp/$ip/22 >/dev/null 2>&1;       return 0    else       return 1    fi }