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2.13. Environment Variables

This section lists all the environment variables that are used directly or indirectly by MySQL. Most of these can also be found in other places in this manual.

Note that any options on the command line take precedence over values specified in option files and environment variables, and values in option files take precedence over values in environment variables.

In many cases, it is preferable to use an option file instead of environment variables to modify the behavior of MySQL. See Section 4.2.3.3, “Using Option Files”.

Variable Description
CXX The name of your C++ compiler (for running configure).
CC The name of your C compiler (for running configure).
CFLAGS Flags for your C compiler (for running configure).
CXXFLAGS Flags for your C++ compiler (for running configure).
DBI_USER The default user name for Perl DBI.
DBI_TRACE Trace options for Perl DBI.
HOME The default path for the mysql history file is $HOME/.mysql_history.
LD_RUN_PATH Used to specify the location of libmysqlclient.so.
MYSQL_DEBUG Debug trace options when debugging.
MYSQL_GROUP_SUFFIX Option group suffix value (like specifying --defaults-group-suffix).
MYSQL_HISTFILE The path to the mysql history file. If this variable is set, its value overrides the default for $HOME/.mysql_history.
MYSQL_HOME The path to the directory in which the server-specific my.cnf file resides (as of MySQL 5.0.3).
MYSQL_HOST The default host name used by the mysql command-line client.
MYSQL_PS1 The command prompt to use in the mysql command-line client.
MYSQL_PWD The default password when connecting to mysqld. Note that using this is insecure. See Section 5.4.2.2, “End-User Guidelines for Password Security”.
MYSQL_TCP_PORT The default TCP/IP port number.
MYSQL_UNIX_PORT The default Unix socket file name; used for connections to localhost.
PATH Used by the shell to find MySQL programs.
TMPDIR The directory where temporary files are created.
TZ This should be set to your local time zone. See Section A.5.4.6, “Time Zone Problems”.
UMASK The user-file creation mode when creating files. See note following table.
UMASK_DIR The user-directory creation mode when creating directories. See note following table.
USER The default user name on Windows and NetWare used when connecting to mysqld.

The UMASK and UMASK_DIR variables, despite their names, are used as modes, not masks:

  • If UMASK is set, mysqld uses ($UMASK | 0600) as the mode for file creation, so that newly created files have a mode in the range from 0600 to 0666 (all values octal).

  • If UMASK_DIR is set, mysqld uses ($UMASK_DIR | 0700) as the base mode for directory creation, which then is AND-ed with ~(~$UMASK & 0666), so that newly created directories have a mode in the range from 0700 to 0777 (all values octal). The AND operation may remove read and write permissions from the directory mode, but not execute permissions.

In MySQL 3.23.25 and above, MySQL assumes that the value for UMASK or UMASK_DIR is in octal if it starts with a zero.


User Comments

Posted by Alexander Janssen on July 30 2006 4:03pm[Delete] [Edit]

Warning: Debian Backports is currently (as of 30th of July 2006) offering version 5.0.22-Debian_2bpo1-log which has a severe problem with handling the MYSQL_HISTFILE.

The manual-page says:

---8<---
On Unix, the mysql client writes a record of executed statements to a
history file. By default, the history file is named .mysql_history and
is created in your home directory. To specify a different file, set the
value of the MYSQL_HISTFILE environment variable.

If you do not want to maintain a history file, first remove
.mysql_history if it exists, and then use either of the following
techniques:

o Set the MYSQL_HISTFILE variable to /dev/null. To cause this setting
to take effect each time you log in, put the setting in one of your
shell's startup files.

o Create .mysql_history as a symbolic link to /dev/null:

shell> ln -s /dev/null $HOME/.mysql_history
You need do this only once.
--->8---

BOTH POSSIBILITIES ARE BROKEN! THEY BOTH DELETE /dev/null !!!
Be warned. I really mean it. A damaged /dev/null brakes your server.

Alex.

Resources:
http://www.bloglines.com/blog/ITnomad?id=125

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