fswatch_rsync.sh

#!/usr/bin/env bash
# 
# DEPENDS ON: dialog, fswatch, rsync, ssh
# 
# This script uses fswatch to monitor a directory for changes and when changes are detected
# Runs rsync to sync the changes to a remote server
#
# Features: 
#  - prompt for initial sync from remote server
#  - delay after rsync to make sure it doesn't run too frequently
#  - uses an SSH socket file to keep the connection open
#


LOCAL="$1"
REMOTE="$2"

# split REMOTE by comma into two vars 
IFS=: read REMOTE_HOST REMOTE_DIR <<<"$REMOTE"


# check that vars above are set 
[ -z "$LOCAL" ] && { echo "Missing LOCAL"; exit 1; }
[ -z "$REMOTE" ] && { echo "Missing REMOTE"; exit 1; }
# check if local is a directory
[ ! -d "$LOCAL" ] && { echo "LOCAL='$LOCAL' does not exist"; exit 1; }
[ -z "$REMOTE_DIR" ] && { echo "Missing REMOTE_DIR (please specify host:/path)"; exit 1; }

for CHECK_CMD in dialog rsync fswatch; do 
  if ! command -v $CHECK_CMD >/dev/null 2>&1; then
    echo "Missing \"$CHECK_CMD\" command."
    echo "You might be able to install with \"brew install $CHECK_CMD\""
    exit 1
  fi
done


MSG="$(printf "Perform initial remote to local sync?\nLOCAL=%s\nREMOTE=%s" "$LOCAL" "$REMOTE")"
SOCK="watch_dir_$$_$REMOTE_HOST.sock"
echo Using SSH socket file $SOCK
ssh -S $SOCK $REMOTE_HOST -M -f -N
ssh -S $SOCK $REMOTE_HOST -O check

if dialog --yesno "$MSG" 10 60; then
  echo do local sync
  rsync -rtli --delete -e "ssh -S $SOCK" "$REMOTE_HOST:$REMOTE_DIR/" "$LOCAL/"
fi;

echo "Listening for changes"
fswatch -r -o "$LOCAL" | while read c; do
  echo "$c changes detected";
  rsync -rtli --delete -e "ssh -S $SOCK" "$LOCAL/" "$REMOTE_HOST:$REMOTE_DIR/"
  # delay before watching for changes again
  sleep 3
  echo "Sync done waiting for changes"
done;