[root@dba ~]# myisampack
myisampack Ver 1.23 for Linux on x86_64
Copyright 2002-2008 MySQL AB, 2008 Sun Microsystems, Inc.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL license

Pack a MyISAM-table to take much less space.
Keys are not updated, you must run myisamchk -rq on the datafile
afterwards to update the keys.
You should give the .MYI file as the filename argument.

Usage: myisampack [OPTIONS] filename...
  -b, --backup        Make a backup of the table as table_name.OLD.
  --character-sets-dir=name
                      Directory where character sets are.
  -#, --debug[=name]  Output debug log. Often this is 'd:t:o,filename'.
  -f, --force         Force packing of table even if it gets bigger or if
                      tempfile exists.
  -j, --join=name     Join all given tables into 'new_table_name'. All tables
                      MUST have identical layouts.
  -?, --help          Display this help and exit.
  -s, --silent        Be more silent.
  -T, --tmpdir=name   Use temporary directory to store temporary table.
  -t, --test          Don't pack table, only test packing it.
  -v, --verbose       Write info about progress and packing result. Use many -v
                      for more verbosity!
  -V, --version       Output version information and exit.
  -w, --wait          Wait and retry if table is in use.

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf /usr/etc/my.cnf ~/.my.cnf
The following groups are read: myisampack
The following options may be given as the first argument:
--print-defaults        Print the program argument list and exit.
--no-defaults           Don't read default options from any option file,
                        except for login file.
--defaults-file=#       Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=#
                        Also read groups with concat(group, suffix)
--login-path=#          Read this path from the login file.

Variables (--variable-name=value)
and boolean options {FALSE|TRUE}  Value (after reading options)
--------------------------------- ----------------------------------------
backup                            FALSE
character-sets-dir                (No default value)
join                              (No default value)
wait                              FALSE
[root@dba ~]# mysqladmin
mysqladmin  Ver 8.42 Distrib 5.6.23, for Linux on x86_64
Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Administration program for the mysqld daemon.
Usage: mysqladmin [OPTIONS] command command....
  --bind-address=name IP address to bind to.
  -c, --count=#       Number of iterations to make. This works with -i
                      (--sleep) only.
  --debug-check       Check memory and open file usage at exit.
  --debug-info        Print some debug info at exit.
  -f, --force         Don't ask for confirmation on drop database; with
                      multiple commands, continue even if an error occurs.
  -C, --compress      Use compression in server/client protocol.
  --character-sets-dir=name
                      Directory for character set files.
  --default-character-set=name
                      Set the default character set.
  -?, --help          Display this help and exit.
  -h, --host=name     Connect to host.
  -b, --no-beep       Turn off beep on error.
  -p, --password[=name]
                      Password to use when connecting to server. If password is
                      not given it's asked from the tty.
  -P, --port=#        Port number to use for connection or 0 for default to, in
                      order of preference, my.cnf, $MYSQL_TCP_PORT,
                      /etc/services, built-in default (3306).
  --protocol=name     The protocol to use for connection (tcp, socket, pipe,
                      memory).
  -r, --relative      Show difference between current and previous values when
                      used with -i. Currently only works with extended-status.
  --secure-auth       Refuse client connecting to server if it uses old
                      (pre-4.1.1) protocol.
                      (Defaults to on; use --skip-secure-auth to disable.)
  -s, --silent        Silently exit if one can't connect to server.
  -S, --socket=name   The socket file to use for connection.
  -i, --sleep=#       Execute commands repeatedly with a sleep between.
  --ssl               Enable SSL for connection (automatically enabled with
                      other flags).
  --ssl-ca=name       CA file in PEM format (check OpenSSL docs, implies
                      --ssl).
  --ssl-capath=name   CA directory (check OpenSSL docs, implies --ssl).
  --ssl-cert=name     X509 cert in PEM format (implies --ssl).
  --ssl-cipher=name   SSL cipher to use (implies --ssl).
  --ssl-key=name      X509 key in PEM format (implies --ssl).
  --ssl-crl=name      Certificate revocation list (implies --ssl).
  --ssl-crlpath=name  Certificate revocation list path (implies --ssl).
  --ssl-verify-server-cert
                      Verify server's "Common Name" in its cert against
                      hostname used when connecting. This option is disabled by
                      default.
  -u, --user=name     User for login if not current user.
  -v, --verbose       Write more information.
  -V, --version       Output version information and exit.
  -E, --vertical      Print output vertically. Is similar to --relative, but
                      prints output vertically.
  -w, --wait[=#]      Wait and retry if connection is down.
  --connect-timeout=#
  --shutdown-timeout=#
  --plugin-dir=name   Directory for client-side plugins.
  --default-auth=name Default authentication client-side plugin to use.
  --enable-cleartext-plugin
                      Enable/disable the clear text authentication plugin.

Variables (--variable-name=value)
and boolean options {FALSE|TRUE}  Value (after reading options)
--------------------------------- ----------------------------------------
bind-address                      (No default value)
count                             0
debug-check                       FALSE
debug-info                        FALSE
force                             FALSE
compress                          FALSE
character-sets-dir                (No default value)
default-character-set             auto
host                              (No default value)
no-beep                           FALSE
port                              0
relative                          FALSE
secure-auth                       TRUE
socket                            (No default value)
sleep                             0
ssl                               FALSE
ssl-ca                            (No default value)
ssl-capath                        (No default value)
ssl-cert                          (No default value)
ssl-cipher                        (No default value)
ssl-key                           (No default value)
ssl-crl                           (No default value)
ssl-crlpath                       (No default value)
ssl-verify-server-cert            FALSE
user                              (No default value)
verbose                           FALSE
vertical                          FALSE
connect-timeout                   43200
shutdown-timeout                  3600
plugin-dir                        (No default value)
default-auth                      (No default value)
enable-cleartext-plugin           FALSE

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf /usr/etc/my.cnf ~/.my.cnf
The following groups are read: mysqladmin client
The following options may be given as the first argument:
--print-defaults        Print the program argument list and exit.
--no-defaults           Don't read default options from any option file,
                        except for login file.
--defaults-file=#       Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=#
                        Also read groups with concat(group, suffix)
--login-path=#          Read this path from the login file.

Where command is a one or more of: (Commands may be shortened)
  create databasename Create a new database
  debug   Instruct server to write debug information to log
  drop databasename Delete a database and all its tables
  extended-status       Gives an extended status message from the server
  flush-hosts           Flush all cached hosts
  flush-logs            Flush all logs
  flush-status  Clear status variables
  flush-tables          Flush all tables
  flush-threads         Flush the thread cache
  flush-privileges      Reload grant tables (same as reload)
  kill id,id,... Kill mysql threads
  password [new-password] Change old password to new-password in current format
  old-password [new-password] Change old password to new-password in old format
  ping   Check if mysqld is alive
  processlist  Show list of active threads in server
  reload  Reload grant tables
  refresh  Flush all tables and close and open logfiles
  shutdown  Take server down
  status  Gives a short status message from the server
  start-slave  Start slave
  stop-slave  Stop slave
  variables             Prints variables available
  version  Get version info from server

[root@dba ~]# mysql -u root -p123456 -e "select user,host from mysql.user";
Warning: Using a password on the command line interface can be insecure.
+---------+-----------+
| user    | host      |
+---------+-----------+
| hufei   | %         |
| root    | %         |
| root    | 127.0.0.1 |
| root    | ::1       |
| feihong | localhost |
| hufei   | localhost |
| root    | localhost |
+---------+-----------+

[root@dba ~]# mysql -u root -p123456 -e "select user,host from mysql.user;select count(*) from test.t"
Warning: Using a password on the command line interface can be insecure.
+---------+-----------+
| user    | host      |
+---------+-----------+
| hufei   | %         |
| root    | %         |
| root    | 127.0.0.1 |
| root    | ::1       |
| feihong | localhost |
| hufei   | localhost |
| root    | localhost |
+---------+-----------+
+----------+
| count(*) |
+----------+
|        8 |
+----------+

[root@dba ~]# mysql -u root -p123456 -s -e "select user,host from mysql.user;select count(*) from test.t"
Warning: Using a password on the command line interface can be insecure.
user host
hufei %
root %
root 127.0.0.1
root ::1
feihong localhost
hufei localhost
root localhost
count(*)
8

[root@dba ~]# mysql -u root -p123456 -E -e "select user,host from mysql.user;select count(*) from test.t"
Warning: Using a password on the command line interface can be insecure.
*************************** 1. row ***************************
user: hufei
host: %
*************************** 2. row ***************************
user: root
host: %
*************************** 3. row ***************************
user: root
host: 127.0.0.1
*************************** 4. row ***************************
user: root
host: ::1
*************************** 5. row ***************************
user: feihong
host: localhost
*************************** 6. row ***************************
user: hufei
host: localhost
*************************** 7. row ***************************
user: root
host: localhost
*************************** 1. row ***************************
count(*): 8

mysql> show full columns from t;
+-------+-------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
| Field | Type        | Collation       | Null | Key | Default | Extra          | Privileges                      | Comment |
+-------+-------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
| id    | int(11)     | NULL            | NO   | PRI | NULL    | auto_increment | select,insert,update,references |         |
| name  | varchar(50) | utf8_general_ci | YES  |     | NULL    |                | select,insert,update,references |         |
+-------+-------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
2 rows in set (0.00 sec)

mysql> show index from t;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| t     |          0 | PRIMARY  |            1 | id          | A         |           8 |     NULL | NULL   |      | BTREE      |         |               |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
1 row in set (0.00 sec)

[root@dba ~]# mysqlshow -uroot -p test t -k
Enter password:
Database: test  Table: t
+-------+-------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
| Field | Type        | Collation       | Null | Key | Default | Extra          | Privileges                      | Comment |
+-------+-------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
| id    | int(11)     |                 | NO   | PRI |         | auto_increment | select,insert,update,references |         |
| name  | varchar(50) | utf8_general_ci | YES  |     |         |                | select,insert,update,references |         |
+-------+-------------+-----------------+------+-----+---------+----------------+---------------------------------+---------+
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| t     | 0          | PRIMARY  | 1            | id          | A         | 8           |          |        |      | BTREE      |         |               |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

[root@dba ~]# mysqlshow -uroot -p test t -i
Enter password:
Database: test  Wildcard: t
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time         | Update_time | Check_time | Collation       | Checksum | Create_options | Comment |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+
| t    | InnoDB | 10      | Compact    | 8    | 2048           | 16384       | 0               | 0            | 5242880   | 10             | 2015-07-20 13:36:52 |             |            | utf8_general_ci |          |                |         |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+-----------------+----------+----------------+---------+

[root@dba ~]# perror 30 60
OS error code  30:  Read-only file system
OS error code  60:  Device not a stream

[root@dba ~]# cat a
a1 a2 a3
b1 b2 b3
[root@dba ~]# replace a1 aa1 b1 bb1 -- a
a converted
[root@dba ~]# cat a
aa1 a2 a3
bb1 b2 b3

[root@dba ~]# replace a c b d < a
cc1 c2 c3
dd1 d2 d3
[root@dba ~]# cat a
aa1 a2 a3
bb1 b2 b3