Rsync with --link-dest wrapper

rsync-link-dest.sh

#!/bin/bash

DATE_FMT="%Y-%m-%dT%H:%M:%S"
BACKUP_PREFIX="backup"

E_ARGS=1
E_NO_SOURCE_DIR=2
E_NO_DEST_DIR=3
E_RSYNC_FAIL=4

if [ $# -lt 2 ]; then
  echo "Usage: ${0} <source dir> <dest dir>"
  exit $E_ARGS
fi

SOURCE_DIR=${1%/}
DEST_DIR=${2%/}

if [ ! -d $SOURCE_DIR ]; then
  echo "'$SOURCE_DIR' is not a directory"
  exit $E_NO_SOURCE_DIR
fi

if [ ! -d $DEST_DIR ]; then
  echo "'$DEST_DIR' is not a directory"
  exit $E_NO_DEST_DIR
fi

SOURCE_DIR=$(readlink -f $SOURCE_DIR)
DEST_DIR=$(readlink -f $DEST_DIR)

DATE_STR=$(date "+$DATE_FMT")
BACKUP_DIR_NAME="$BACKUP_PREFIX-$DATE_STR"

# If there's no 'current' backup then we need to make an initial backup
CURRENT_LINK="$DEST_DIR/current"
if [ ! -h "$CURRENT_LINK" ]; then
  echo "Creating initial backup in $DEST_DIR/$BACKUP_DIR_NAME"
  rsync -aP "$SOURCE_DIR/" "$DEST_DIR/$BACKUP_DIR_NAME"

  if [ $? -ne 0 ]; then
    echo "Rsync failed; aborting" 
    exit $E_RSYNC_FAIL
  fi

else
  PREV_BACKUP_DIR_NAME=$(readlink -f $CURRENT_LINK)
  echo "Creating incremental backup using '$PREV_BACKUP_DIR_NAME' as a base"
  rsync -aP --link-dest="$PREV_BACKUP_DIR_NAME" "$SOURCE_DIR/" "$DEST_DIR/$BACKUP_DIR_NAME"

  if [ $? -ne 0 ]; then
    echo "Rsync failed; aborting" 
    exit $E_RSYNC_FAIL
  fi

  unlink "$CURRENT_LINK"
fi

# Set the 'current' backup
ln -s $BACKUP_DIR_NAME $DEST_DIR/current

exit 0