Options are given after the command name.

An option argument begins with one dash or two dashes, depending on whether it is a short form or long form of the option name. Many options have both short and long forms. For example, -? and --help are the short and long forms of the option that instructs a MySQL program to display its help message.

Option names are case-sensitive. -v and -V are both legal and have different meanings. (They are the corresponding short forms of the --verbose and --version options.)

Some options take a value following the option name. For example, -h localhost or --host=localhost indicate the MySQL server host to a client program. The option value tells the program the name of the host where the MySQL server is running.

For a long option that takes a value, separate the option name and the value by an = sign. For a short option that takes a value, the option value can immediately follow the option letter, or there can be a space between: -hlocalhost and -h localhost are equivalent. An exception to this rule is the option for specifying your MySQL password. This option can be given in long form as --password=pass_val or as --password. In the latter case (with no password value given), the program interactively prompts you for the password. The password option also may be given in short form as -ppass_val or as -p. However, for the short form, if the password value is given, it must follow the option letter with no intervening space: If a space follows the option letter, the program has no way to tell whether a following argument is supposed to be the password value or some other kind of argument. Consequently, the following two commands have two completely different meanings:

mysql -ptest
mysql -p test

The first command instructs mysql to use a password value of test, but specifies no default database. The second instructs mysql to prompt for the password value and to use test as the default database.

Within option names, dash (-) and underscore (_) may be used interchangeably in most cases, although the leading dashes cannot be given as underscores. For example, --skip-grant-tables and --skip_grant_tables are equivalent.

In this Manual, we use dashes in option names, except where underscores are significant. This is the case with, for example, --log-bin and --log_bin, which are different options. We encourage you to do so as well.

The MySQL server has certain command options that may be specified only at startup, and a set of system variables, some of which may be set at startup, at runtime, or both. System variable names use underscores rather than dashes, and when referenced at runtime (for example, using SET or SELECT statements), must be written using underscores:

SET GLOBAL general_log = ON;
SELECT @@GLOBAL.general_log;

At server startup, the syntax for system variables is the same as for command options, so within variable names, dashes and underscores may be used interchangeably. For example, --general_log=ON and --general-log=ON are equivalent. (This is also true for system variables set within option files.)

For options that take a numeric value, the value can be given with a suffix of K, M, or G (either uppercase or lowercase) to indicate a multiplier of 1024, 1024² or 1024³. For example, the following command tells mysqladmin to ping the server 1024 times, sleeping 10 seconds between each ping:

mysqladmin --count=1K --sleep=10 ping

When specifying file names as option values, avoid the use of the ~ shell metacharacter. It might not be interpreted as you expect.