mkbackup.sh

# Manage backups using SHA256 values. (Inspired by hash tables, but far poorer by design.)
# Syntax: mkbackup.sh [filename]
# WIP: Migrate to python3.
# WIP: Remove table and tarball entries based on backup_dir contents.


# Create a csv table: filename,sha256sum_of_filename
BackUp()
{

  # Set backup directory.
  backup_dir="$1"

  # Send filename to a tar archive, if it's new.
  toArchive()
  {
    if [[ $1 == "pass" ]]; then
      return 0
    else
        filename="$2"
        if [[ $1 == "append" ]]; then
          mode="-rf"
        # If a second parameter is passed, use it as the tarball filename.
        else
          mode="-uf"
        if [[ "$3" ]]; then
          tarball="$3"
        fi
        # Append to the tarball directory.
        tar $mode $tarball "$filename"
        echo "$filename added to $tarball.\n "
      fi
    fi
  }

  # Test existing entries.
  testEntry()
  {
    filename="$1"
    tarball="$USER-backup.tar"
    sha="$2"
    if [[ $3 ]]; then
      backup_table="$3"
    else
      backup_table="backup_table"
    fi
    # Test if the filename is there, but the SHA value changed.
    if [[ $(grep "$filename," $backup_table) ]] && [[ ! $(grep "$sha" $backup_table) ]]; then
        # Remove trailing characters
      filename_sed="${filename//\//\\/}"
        sed -i "s/$filename_sed,.*/$filename_sed,$sha/g" $backup_table && \
        echo "Entry updated."
      mode="append"
      unset filename_sed
    # Check if the file isn't in the tarball.
    elif [[ ! $(tar -tf $tarball 2> /dev/null | grep -w "$filename") ]]; then
      # If the entry does not exist at all, add it.
      if [[ ! $(grep -w "$filename,$sha" $backup_table) ]]; then
        # If it is not there exactly, append it to the table.
        echo "$filename,$sha" >> $backup_table && \
        echo "Added entry to table."
      fi
      mode="update"
    # If it's there and unchanged, a null value will stop toArchive() from running.
    else
      filename=""
      mode="pass"
    fi
    # If something should be sent to a tar archive, send it.
    toArchive "$mode" "$filename"
  }

  # Loop through everything in the backup directory.
  loopDir()
  {
    for i in "$1"/*; do
      if [ -d "$i" ]; then
        echo "dir: $i" && \
        loopDir "$i"
      elif [ -f "$i" ]; then
        filename="$i"
        echo "file: $filename"
        sha=$(sha256sum "$filename" | sed 's/ .*//g')
        testEntry "$filename" "$sha"
      fi
    done
  }

  # Init.
  loopDir $backup_dir
  # You could even build on it:
  #gzip2 $tarball
  #gpg2 --cipher-algo AES-256 $tarball
  #rsync -v $encrypted_file user@server:/backup/storage/space

}


BackUp "$1"