Ajuda com script pronto

[podestafox]

Achei este script na web, mas ao executar apresenta a seguinte
mensagem de erro:

backup.sh: 19: Syntax error: "(" unexpected

Aqui o código fonte do script:

#!/usr/bin/bash
#
# Author  : Antonio Jozzolino <address@hidden>
# Site    : http://www.sgd.com.br
# Since   : Tue, 3 June 2008 14:01:36 GMT
# Changed : Tue, 3 June 2008 15:23:14 GMT
# See     : http://www.sgd.com.br/content/view/40/1/


#Variable
sr="mysql.user.com.br" #remote server
lg="mysql_user"        #login name
pw="123456"            #password
hs="all"               #file name to store sql file
bk="$HOME/dbackup"     #path to store backup files
nw=$(date "+%Y%m%d")   #get date as string
nb=60                  #maximum number of files that will be keep

function backup()
{
  echo "Getting data from mysql server"
  mysqldump -u$lg -p$pw -h$sr --add-drop-table --quote-names
--all-databases --add-drop-database > "$HOME/"$hs.sql
  echo "Compressing $hs.sql.gz file ..."
  gzip -f "$HOME/"$hs.sql
  if [ -d $bk ]; then
    continue
  else
    mkdir $bk
  fi
  cp -f "$HOME/"$hs.sql.gz "$bk/$nw.sql.gz"

  a=0
  b=$(ls -t $bk)
  c=$nb

  for arq in $b; do
    a=$(($a+1))
    if [ "$a" -gt $c ];  then
      rm -f "$bk/$arq"
    fi
  done
}

backup