Syntax:
SHOW GRANTS [FOR user]

This statement lists the GRANT statement or statements that must be
issued to duplicate the privileges that are granted to a MySQL user
account. SHOW GRANTS requires the SELECT privilege for the mysql
database, except to see the privileges for the current user.

The account is named using the same format as for the GRANT statement;
for example, 'jeffrey'@'localhost'. If you specify only the user name
part of the account name, a host name part of '%' is used. For
additional information about specifying account names, see [HELP
GRANT].

mysql> SHOW GRANTS FOR 'root'@'localhost';
+---------------------------------------------------------------------+
| Grants for root@localhost                                           |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+

To list the privileges granted to the account that you are using to
connect to the server, you can use any of the following statements:

SHOW GRANTS;
SHOW GRANTS FOR CURRENT_USER;
SHOW GRANTS FOR CURRENT_USER();

If SHOW GRANTS FOR CURRENT_USER (or any of the equivalent syntaxes) is
used in DEFINER context, such as within a stored procedure that is
defined with SQL SECURITY DEFINER), the grants displayed are those of
the definer and not the invoker.

SHOW GRANTS displays only the privileges granted explicitly to the
named account. Other privileges might be available to the account, but
they are not displayed. For example, if an anonymous account exists,
the named account might be able to use its privileges, but SHOW GRANTS
will not display them.

URL: http://dev.mysql.com/doc/refman/5.6/en/show-grants.html

