(mysql.info.gz) Program variables

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(mysql.info.gz) Program Options

 
 4.3.4 Using Options to Set Program Variables
 --------------------------------------------
 
 Many MySQL programs have internal variables that can be set at runtime.
 As of MySQL 4.0.2, 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.
 
 Prior to MySQL 4.0.2, program variable names are not recognized as
 option names.  Instead, use the `--set-variable' option to assign a
 value to a variable:
 
      shell> mysql --set-variable=max_allowed_packet=16777216
      shell> mysql --set-variable=max_allowed_packet=16M
 
 In an option file, omit the leading dashes:
 
      [mysql]
      set-variable = max_allowed_packet=16777216
 
 Or:
 
      [mysql]
      set-variable = max_allowed_packet=16M
 
 With `--set-variable', underscores in variable names cannot be given as
 dashes for versions of MySQL older than 4.0.2.
 
 The `--set-variable' option is still recognized in MySQL 4.0.2 and up,
 but is deprecated.
 
 Some server variables can be set at runtime. For details, see 
 Dynamic System Variables.
 

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