ssh_port_forward.sh - SSH Port Forwarding Bash Script

#!/bin/sh
#
# [ssh_port_forward.sh]
#
# SSH port forwarding script.
#
# syntax: ssh -L <local_port>:<destination_address>:<destination_port> <host_address|user@host_address>
# eg:
# ssh -L 21121:SkyLake.Centauri.dev:21 phr0z3n@IvyBridge.Centauri.dev
# ssh -L 21121:SkyLake.Centauri.dev:21 phr0z3n@SkyLake.Centauri.dev             # For complete transmission encryption.
#

if [ -z "$4" ]; then                    # If argument 4 is blank...
    echo "Usage: $0 <local_port> <destination_address> <destination_port> <host_address|user@host_address>"
    exit
fi

if [ "$5" ]; then                       # If argument 5 is not blank...
    echo "Usage: $0 <local_port> <destination_address> <destination_port> <host_address|user@host_address>"
    exit
fi

ssh -L $1:$2:$3 $4