bash script - check if mysql database exists peform action based on result
#!/bin/bash
## --user=XXXXXX --password=XXXXXX *may* not be necessary if run as root or you have unsecured DBs but
##   using them makes this script a lot more portable.  Thanks @billkarwin
RESULT=`mysqlshow --user=XXXXXX --password=XXXXXX myDatabase| grep -v Wildcard | grep -o myDatabase`
if [ "$RESULT" == "myDatabase" ]; then
    echo YES
fi

[root@host ~]# mysqlshow myDatabase
Wildcard: myDatabase
+------------------+
|    Databases     |
+------------------+
| myDatabase       |
+------------------+

[root@host ~]# mysqlshow myDatabase
Wildcard: myDatabase
+-----------+
| Databases |
+-----------+
+-----------+

if [ -d /var/lib/mysql/databasename ] ; then ...

for db in $(mysql -u -p -N <<<"show databases like '%something%'")
do
  case $db in
    "something")
      // do something
    ;;
    "something else")
      // do something else
    ;;
  esac
done

RESULT=`mysql -u $USER -p$PASSWORD --skip-column-names -e "SHOW DATABASES LIKE 'myDatabase'"`
if [ "$RESULT" == "myDatabase" ]; then
    echo "Database exist"
else
    echo "Database does not exist"
fi