Chapter 4. Using MySQL Programs

Table of Contents

4.1. Overview of MySQL Programs
4.2. Invoking MySQL Programs
4.3. Specifying Program Options
4.3.1. Using Options on the Command Line
4.3.2. Using Option Files
4.3.3. Using Environment Variables to Specify Options
4.3.4. Using Options to Set Program Variables

This chapter provides a brief overview of the command-line programs provided by MySQL AB and discusses how to specify options when you run these programs. Most programs have options that are specific to their own operation, but the syntax for specifying options is similar for all of them. Later chapters provide more detailed descriptions of individual programs, including which options they recognize.

MySQL AB also provide three GUI client programs for use with the MySQL server:

4.1. Overview of MySQL Programs

MySQL AB provides several types of programs:

  • The MYSQL server and server startup scripts:

    • mysqld is the MySQL server

    • mysqld_safe, mysql.server, and mysqld_multi are server startup scripts

    • mysql_install_db initializes the data directory and the initial databases

    These programs are discussed further in Chapter 5, Database Administration.

  • Client programs that access the server:

    • mysql is a command-line client for executing SQL statements interactively or in batch mode.

    • mysqladmin is an administrative client.

    • mysqlcheck performs table maintenance operations

    • mysqldump and mysqlhotcopy make database backups.

    • mysqlimport imports data files.

    • mysqlshow displays information about databases and tables.

    These programs are discussed further in Chapter 8, Client and Utility Programs.

  • Utility programs that operate independently of the server:

    • myisamchk performs table maintenance operations.

    • myisampack produces compressed, read-only tables.

    • mysqlbinlog is a tool for processing binary log files.

    • perror displays error code meanings.

    myisamchk is discussed further in Chapter 5, Database Administration. The other programs are further in Chapter 8, Client and Utility Programs.

Most MySQL distributions include all of these programs, except for those programs that are platform-specific. (For example, the server startup scripts are not used on Windows.) The exception is that RPM distributions are more specialized. There is one RPM for the server, another for the client programs, and so forth. If you appear to be missing one or more programs, see Chapter 2, Installing MySQL for information on types of distributions and what they contain. It may be that you need to install something else.

4.2. Invoking MySQL Programs

To invoke a MySQL program from the command line (that is, from your shell or command prompt), enter the program name followed by any options or other arguments needed to instruct the program what you want it to do. The following commands show some sample program invocations. “shell>” represents the prompt for your command interpreter; it is not part of what you type. The particular prompt you see depends on your command interpreter. Typical prompts are $ for sh or bash, % for csh or tcsh, and C:\> for Windows command.com or cmd.exe.

shell> mysql test
shell> mysqladmin extended-status variables
shell> mysqlshow --help
shell> mysqldump --user=root personnel

Arguments that begin with a dash are option arguments. They typically specify the type of connection a program should make to the server or affect its operational mode. Options have a syntax that is described in Section 4.3, “Specifying Program Options”.

Non-option arguments (arguments with no leading dash) provide additional information to the program. For example, the mysql program interprets the first non-option argument as a database name, so the command mysql test indicates that you want to use the test database.

Later sections that describe individual programs indicate which options a program understands and describe the meaning of any additional non-option arguments.

Some options are common to a number of programs. The most common of these are the --host, --user, and --password options that specify connection parameters. They indicate the host where the MySQL server is running, and the username and password of your MySQL account. All MySQL client programs understand these options; they allow you to specify which server to connect to and the account to use on that server.

You may find it necessary to invoke MySQL programs using the pathname to the bin directory in which they are installed. This is likely to be the case if you get a “program not found” error whenever you attempt to run a MySQL program from any directory other than the bin directory. To make it more convenient to use MySQL, you can add the pathname of the bin directory to your PATH environment variable setting. Then to run a program you need only type its name, not its entire pathname.

Consult the documentation for your command interpreter for instructions on setting your PATH. The syntax for setting environment variables is interpreter-specific.

4.3. Specifying Program Options

You can provide options for MySQL programs in several ways:

  • On the command line following the program name. This is most common for options that apply to a specific invocation of the program.

  • In an option file that the program reads when it starts. This is common for options that you want the program to use each time it runs.

  • In environment variables. These are useful for options that you want to apply each time the program runs, although in practice option files are used more commonly for this purpose. (Section 5.12.2, “Running Multiple Servers on Unix” discusses one situation in which environment variables can be very helpful. It describes a handy technique that uses such variables to specify the TCP/IP port number and Unix socket file for both the server and client programs.)

MySQL programs determine which options are given first by examining environment variables, then option files, and then the command line. If an option is specified multiple times, the last occurrence takes precedence. This means that environment variables have the lowest precedence and command-line options the highest.

You can take advantage of the way that MySQL programs process options by specifying the default values for a program's options in an option file. Then you need not type them each time you run the program, but can override the defaults if necessary by using command-line options.

4.3.1. Using Options on the Command Line

Program options specified on the command line follow these rules:

  • Options are given after the command name.

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

    shell> mysql -ptest
    shell> 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.

Some options control behavior that can be turned on or off. For example, the mysql client supports a --column-names option that determines whether or not to display a row of column names at the beginning of query results. By default, this option is enabled. However, you may want to disable it in some instances, such as when sending the output of mysql into another program that expects to see only data and not an initial header line.

To disable column names, you can specify the option using any of these forms:

--disable-column-names
--skip-column-names
--column-names=0

The --disable and --skip prefixes and the =0 suffix all have the same effect: They turn the option off.

The “enabled” form of the option may be specified in any of these ways:

--column-names
--enable-column-names
--column-names=1

If an option is prefixed by --loose, the program does not exit with an error if it does not recognize the option, but instead issues only a warning:

shell> mysql --loose-no-such-option
mysql: WARNING: unknown option '--no-such-option'

The --loose prefix can be useful when you run programs from multiple installations of MySQL on the same machine. This prefix is particularly useful when you list options in an option file. An option that may not be recognized by all versions of a program can be given using the --loose prefix (or loose in an option file). Versions of the program that do not recognize the option issue a warning and ignore the option. convention.

Another option which may be occasionally useful with mysql is the -e or --execute option, which can be used to pass SQL statements to the server. The statements must be surrounded by (single or double) quotation marks. (However, if you wish to use quoted values within the query, then you should use double quotes for the query, and single quotes for any quoted values within the query.) When this option is used, the statements are executed, and then mysql exits to the command shell immediately thereafter.

For example, you can use the following to obtain a list of user accounts:

shell> mysql -u root -p -e "SELECT User, Host FROM user" mysql
Enter password: ******
+------+-----------+
| User | Host      |
+------+-----------+
|      | gigan     |
| root | gigan     |
|      | localhost |
| jon  | localhost |
| root | localhost |
+------+-----------+
shell>

Note that the name of the mysql database was passed as a separate argument. However, the same query could have been executed using mysql -u root -p -e "SELECT User, Host FROM mysql.user" from the shell prompt.

Multiple SQL statements may be passed in this way, separated by semicolons:

shell> mysql -u root -p --execute="SELECT Name FROM Country WHERE Name LIKE 'AU%';SELECT COUNT(*) FROM City" world
Enter password: ******
+-----------+
| Name      |
+-----------+
| Australia |
| Austria   |
+-----------+
+----------+
| COUNT(*) |
+----------+
|     4079 |
+----------+

Note that the long form (--execute) must be followed by an equals sign (=).

The -e option may also be used to pass commands in an analogous fashion to the ndb_mgm management client for MySQL Cluster. See Section 15.3.6, “Safe Shutdown and Restart” for an example.

4.3.2. Using Option Files

MySQL programs can read startup options from option files (also sometimes called configuration files). Option files provide a convenient way to specify commonly used options so that they need not be entered on the command line each time you run a program.

The following programs support option files: myisamchk, myisampack, mysql, mysql.server, mysqladmin, mysqlbinlog, mysqlcc, mysqlcheck, mysqld_safe, mysqldump, mysqld, mysqlhotcopy, mysqlimport, and mysqlshow.

Note: Option files used with MySQL Cluster programs are covered in Section 15.4, “MySQL Cluster Configuration”.

On Windows, MySQL programs read startup options from the following files:

FilenamePurpose
WINDIR\my.iniGlobal options
C:\my.cnfGlobal options
INSTALLDIR\my.iniGlobal Options
defaults-extra-fileThe file specified with --defaults-extra-file=path, if any

WINDIR represents the location of your Windows directory. This is commonly C:\WINDOWS or C:\WINNT. You can determine its exact location from the value of the WINDIR environment variable using the following command:

C:\> echo %WINDIR%

INSTALLDIR represents the installation directory of MySQL. This is typically C:\PROGRAMDIR\MySQL\MySQL 5.0 Server where PROGRAMDIR represents the programs directory (usually Program Files on English-language versions of Windows), when MySQL 5.0 has been installed using the installation and configuration wizards. See Section 2.3.5.14, “The Location of the my.ini File”.

On Unix, MySQL programs read startup options from the following files:

FilenamePurpose
/etc/my.cnfGlobal options
$MYSQL_HOME/my.cnfServer-specific options
defaults-extra-fileThe file specified with --defaults-extra-file=path, if any
~/.my.cnfUser-specific options

MYSQL_HOME is an environment variable containing the path to the directory in which the server-specific my.cnf file resides. (This was DATADIR prior to MySQL version 5.0.3.)

If MYSQL_HOME is not set and there is a my.cnf file in DATADIR and there is no my.cnf file in BASEDIR, mysqld_safe sets MYSQL_HOME to DATADIR. Otherwise, if MYSQL_HOME is not set and there is no my.cnf in DATADIR, then mysqld_safe sets MYSQL_HOME to BASEDIR.

Typically this is /usr/local/mysql/data for a binary installation or /usr/local/var for a source installation. Note that this is the data directory location that was specified at configuration time, not the one specified with --datadir when mysqld starts. Use of --datadir at runtime has no effect on where the server looks for option files, because it looks for them before processing any command-line arguments.

MySQL looks for option files in the order just described and reads any that exist. If an option file that you want to use does not exist, create it with a plain text editor. If multiple option files exist, an option specified in a file read later takes precedence over the same option specified in a file read earlier.

Note: On Unix platforms, MySQL ignores configuration files that are world-writable. This is intentional, and acts as a security measure.

Any long option that may be given on the command line when running a MySQL program can be given in an option file as well. To get the list of available options for a program, run it with the --help option.

The syntax for specifying options in an option file is similar to command-line syntax, except that you omit the leading two dashes. For example, --quick or --host=localhost on the command line should be specified as quick or host=localhost in an option file. To specify an option of the form --loose-opt_name in an option file, write it as loose-opt_name.

Empty lines in option files are ignored. Non-empty lines can take any of the following forms:

  • #comment, ;comment

    Comment lines start with ‘#’ or ‘;’. A ‘#’ comment can start in the middle of a line as well.

  • [group]

    group is the name of the program or group for which you want to set options. After a group line, any opt_name or set-variable lines apply to the named group until the end of the option file or another group line is given.

  • opt_name

    This is equivalent to --opt_name on the command line.

  • opt_name=value

    This is equivalent to --opt_name=value on the command line. In an option file, you can have spaces around the ‘=’ character, something that is not true on the command line. You can quote the value with single quotes or double quotes. This is useful if the value contains a ‘#’ comment character or whitespace.

Leading and trailing blanks are automatically deleted from option names and values. You may use the escape sequences ‘\b’, ‘\t’, ‘\n’, ‘\r’, ‘\\’, and ‘\s’ in option values to represent the backspace, tab, newline, carriage return, and space characters.

On Windows, if an option value represents a pathname, you should specify the value using ‘/’ rather than ‘\’ as the pathname separator. If you use ‘\’, you must double it as ‘\\’, because ‘\’ is the escape character in MySQL.

If an option group name is the same as a program name, options in the group apply specifically to that program.

The [client] option group is read by all client programs (but not by mysqld). This allows you to specify options that apply to all clients. For example, [client] is the perfect group to use to specify the password that you use to connect to the server. (But make sure that the option file is readable and writable only by yourself, so that other people cannot find out your password.) Be sure not to put an option in the [client] group unless it is recognized by all client programs that you use. Programs that do not understand the option quit after displaying an error message if you try to run them.

Beginning MySQL 5.0.4 in the 5.0 series, it is possible to use !include directives in option files to include specific files and !includedir to search specific directories for option files. For example, to include the file /home/mydir/myopt.cnf, you can use the following:

!include /home/me/myopt.cnf

To search the directory /home/mydir for all files ending in .cnf and to read these as option files, you would use:

!includedir /home/mydir

Note that these options are section-specific. For example, suppose that you were to use something in my.cnf such as the following:

[mysqld]
!include /home/mydir/myopt.cnf

In such a case, the file myopt.cnf would be processed only for the server, and the !include directive would be ignored by any client applications. However, if you were to use the following:

[mysqldump]
!includedir /home/mydir/my-dump-options

then the directory /home/mydir/my-dump-options would be checked for option files ending in .cnf by mysqldump only, and not by the server or by any other client applications.

Note: Currently, any files to be found and included using the !includedir directive on Unix operating systems must have filenames ending in .cnf. On Windows, this directive also checks for files with a .ini extension (in addition to .cnf).

If you want to create option groups that should be read by one specific mysqld server release series only, you can do this by using groups with names of [mysqld-4.1], [mysqld-5.0], and so forth. The following group indicates that the --new option should be used only by MySQL servers with 5.0.x version numbers:

[mysqld-5.0]
new

Here is a typical global option file:

[client]
port=3306
socket=/tmp/mysql.sock

[mysqld]
port=3306
socket=/tmp/mysql.sock
key_buffer_size=16M
max_allowed_packet=8M

[mysqldump]
quick

The preceding option file uses var_name=value syntax for the lines that set the key_buffer_size and max_allowed_packet variables.

Here is a typical user option file:

[client]
# The following password will be sent to all standard MySQL clients
password="my_password"

[mysql]
no-auto-rehash
connect_timeout=2

[mysqlhotcopy]
interactive-timeout

If you have a source distribution, you can find sample option files named my-xxxx.cnf in the support-files directory. If you have a binary distribution, look in the support-files directory under your MySQL installation directory. On Windows the sample option files may also be located in the MySQL installation directory (see earlier in this section or Chapter 2, Installing MySQL if you do not know where this is). Currently there are sample option files for small, medium, large, and very large systems. To experiment with one of these files, copy it to C:\my.cnf on Windows or to .my.cnf in your home directory on Unix.

Note: On Windows, the .cnf option file extension might not be displayed.

All MySQL programs that support option files handle the following command-line options:

  • --no-defaults

    Don't read any option files.

  • --print-defaults

    Print the program name and all options that it gets from option files.

  • --defaults-file=path_name

    Use only the given option file. path_name is the full pathname to the file.

  • --defaults-extra-file=path_name

    Read this option file after the global option file but before the user option file. path_name is the full pathname to the file.

To work properly, each of these options must immediately follow the command name on the command line, with the exception that --print-defaults may be used immediately after --defaults-file or --defaults-extra-file.

In shell scripts, you can use the my_print_defaults program to parse option files. The following example shows the output that my_print_defaults might produce when asked to show the options found in the [client] and [mysql] groups:

shell> my_print_defaults client mysql
--port=3306
--socket=/tmp/mysql.sock
--no-auto-rehash

Note for developers: Option file handling is implemented in the C client library simply by processing all matching options (that is, options in the appropriate group) before any command-line arguments. This works nicely for programs that use the last instance of an option that is specified multiple times. If you have a C or C++ program that handles multiply specified options this way but does not read option files, you need add only two lines to give it that capability. Check the source code of any of the standard MySQL clients to see how to do this.

Several other language interfaces to MySQL are based on the C client library, and some of them provide a way to access option file contents. These include Perl and Python. See the documentation for your preferred interface for details.

4.3.3. Using Environment Variables to Specify Options

To specify an option using an environment variable, set the variable using the syntax appropriate for your comment processor. For example, on Windows or NetWare, you can set the USER variable to specify your MySQL account name. To do so, use this syntax:

SET USER=your_name

The syntax on Unix depends on your shell. Suppose that you want to specify the TCP/IP port number using the MYSQL_TCP_PORT variable. Typical syntax (such as for sh, bash, zsh, and so on) is as follows:

MYSQL_TCP_PORT=3306
export MYSQL_TCP_PORT

The first command sets the variable, and the export command exports the variable to the shell environment so that its value becomes accessible to MySQL and other processes.

For csh and tcsh there are similar issues. When running these shells, use setenv to make the shell variable available to the environment:

setenv MYSQL_TCP_PORT 3306

The commands to set environment variables can be executed at your command prompt to take effect immediately. These settings persist until you log out. To have the settings take effect each time you log in, place the appropriate command or commands in a startup file that your command interpreter reads each time it starts. Typical startup files are AUTOEXEC.BAT for Windows, .bash_profile for bash, or .tcshrc for tcsh. Consult the documentation for your command interpreter for specific details.

Appendix F, Environment Variables lists all environment variables that affect MySQL program operation.

4.3.4. Using Options to Set Program Variables

Many MySQL programs have internal variables that can be set at runtime. Program variables are set the same way as any other long option that takes a value. For example, mysql has a max_allowed_packet variable that controls the maximum size of its communication buffer. To set the max_allowed_packet variable for mysql to a value of 16MB, use either of the following commands:

shell> mysql --max_allowed_packet=16777216
shell> mysql --max_allowed_packet=16M

The first command specifies the value in bytes. The second specifies the value in megabytes. Variable values can have a suffix of K, M, or G (either uppercase or lowercase) to indicate units of kilobytes, megabytes, or gigabytes.

In an option file, the variable setting is given without the leading dashes:

[mysql]
max_allowed_packet=16777216

Or:

[mysql]
max_allowed_packet=16M

If you like, underscores in a variable name can be specified as dashes.

Note: The older syntax --set-variable = option=value is still recognized in MySQL 5.0, but is now deprecated.

Some server variables can be set at runtime. For details, see Section 5.3.3.1, “Dynamic System Variables”.