Simple File Sync Using SCP

do_sync.sh

#!/bin/bash
# A very simple script (function) to enable file syncing given a server IP running (open)sshd
#
# rsync is probably a better option... but if you cant, ssh/scp is pretty straightforward
#
# to setup (open)sshd on windows 10 refer to https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_install_firstuse
# to setup (open)sshd on linux / mac refer to your package manager (i.e. apt-get install openssh-server)
#
# This script makes a few assumptions, if you just source this file (source do_sync.sh) then execute "do_sync" to see usage
# NOTE: you need to set the following environment variables: SYNC_HOST and SYNC_USER

function do_sync {
    # $SYNC_HOST is server to scp with
    # $SYNC_USER is user to scp as
    # $1 decides (l2s) local to server or (s2l) server to local (bak) bidirectional bakup
    echo "using: SYNC_HOST ($SYNC_HOST), SYNC_USER ($SYNC_USER)"
    DIRECTION=${1:-invalid}
    LOCAL_PATH=${2:-invalid}
    SERVER_PATH=${3:-invalid}
    LOCAL_HOST=$(cat /etc/hostname)
    if      [ "$DIRECTION" = "bak" ]; then
        echo "backing up server and local files by hostnames"
        scp $SYNC_USER@$SYNC_HOST:$SERVER_PATH $LOCAL_PATH.$SYNC_HOST.bak
        scp $LOCAL_PATH $SYNC_USER@$SYNC_HOST:$SERVER_PATH.$LOCAL_HOST.bak
        cp $LOCAL_PATH $LOCAL_PATH.$LOCAL_HOST.bak
        scp $LOCAL_PATH.$SYNC_HOST.bak $SYNC_USER@$SYNC_HOST:$SERVER_PATH.$SYNC_HOST.bak
    elif    [ "$DIRECTION" = "l2s" ]; then
        echo "replacing server with local file"
        scp $LOCAL_PATH $SYNC_USER@$SYNC_HOST:$SERVER_PATH
    elif    [ "$DIRECTION" = "s2l" ]; then
        echo "replacing local with server file"
        scp $SYNC_USER:$SYNC_HOST:$SERVER_PATH $LOCAL_PATH
    else
        echo "invalid selection(s): '$DIRECTION', '$LOCAL_PATH', '$SERVER_PATH'"
        echo "Usage: do_sync <direction> <local_path> <server_path>"
        echo "  <direction> = l2s (local to server)"
        echo "                s2l (server to local)"
        echo "                bak (bidirectional backup)"
        echo "  <local_path> = path to local file to sync/backup"
        echo "  <server_path> = path to server file to sync/backup"
        echo ""
        echo "SYNC_HOST, SYNC_USER, and LOCAL_HOST can be changed"
        echo "  export SYNC_USER=<server user to scp as>"
        echo "  export SYNC_HOST=<desired server>"
        echo "  export LOCAL_HOST=<local identifier>"
        return 1
    fi
}