在mysql日常操作中，妙用pager設定顯示方式，可以大大提高工作效率。比如select出來的結果集超過幾個螢幕，那麼前面的結果一晃而過無法看到，這時候使用pager可以設定呼叫os的more或者less等顯示查詢結果，和在os中使用more或者less檢視大檔案的效果一樣。
pager用法：
實際上等於將它設定以後的所有mysql操作命令的輸出透過pager設定命令執行，類似於管道符的作用
nopager命令：取消pager設定，恢復之前的輸出狀態。（如果不設定nopager，那麼只能透過重啟mysql服務才能恢復了）
舉些例子來說明吧：
1）當處理大量資料時，不想顯示查詢的結果，而只需知道查詢花費的時間。
mysql> select * from huanqiu.haha; +----+------------+ | id | name | +----+------------+ | 1 | wangshibo | | 2 | wangshikui | | 3 | wangjuan | | 4 | wangman | | 11 | wangshikui | +----+------------+ 5 rows in set (0.00 sec) mysql> pager cat /dev/null; //實際上等於後面執行的命令|cat /dev/null，這樣顯示結果就只是執行時間了 PAGER set to 'cat /dev/null' mysql> select * from huanqiu.haha; 5 rows in set (0.00 sec) mysql> nopager; //恢復之前的輸出狀態 PAGER set to stdout mysql> select * from huanqiu.haha; +----+------------+ | id | name | +----+------------+ | 1 | wangshibo | | 2 | wangshikui | | 3 | wangjuan | | 4 | wangman | | 11 | wangshikui | +----+------------+ 5 rows in set (0.00 sec)
2）如果有大量連線，用show processlist看不方便，想看有多少Sleep狀態，則可以用pager。
mysql> show processlist; +------+-------+---------------------+--------+-------------+------+-----------------------------------------------------------------------+------------------+ | Id | User | Host | db | Command | Time | State | Info | +------+-------+---------------------+--------+-------------+------+-----------------------------------------------------------------------+------------------+ | 5 | root | localhost | huanpc | Query | 0 | init | show processlist | | 1801 | slave | 192.168.1.102:37125 | NULL | Binlog Dump | 9904 | Master has sent all binlog to slave; waiting for binlog to be updated | NULL | +------+-------+---------------------+--------+-------------+------+-----------------------------------------------------------------------+------------------+ 2 rows in set (0.00 sec) mysql> pager grep Sleep |wc -l; PAGER set to 'grep Sleep |wc -l' mysql> show processlist; //類似於show processlist結果再透過grep Sleep |wc -l顯示；下面表示一共有2個連線，其中0個Sleep狀態的連線。 0 2 rows in set (0.00 sec) mysql> nopager; //恢復之前的輸出狀態
3）設定pager，只檢視slave狀態的幾個status值。
mysql> show slave status \G; //其中的\G表示顯示要換行顯示
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.1.101
Master_User: slave
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 5370489
Relay_Log_File: mysql-relay-bin.000005
Relay_Log_Pos: 2476520
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB: huanqiu,huanpc
Replicate_Ignore_DB: mysql
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 5370489
Relay_Log_Space: 2476693
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 101
Master_UUID: b667a58f-d6e0-11e6-8c0a-fa163e2d66ac
Master_Info_File: /data/mysql/data/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> pager cat | egrep -i 'system user|Exec_Master_Log_Pos|Seconds_Behind_Master|Read_Master_Log_Pos';
PAGER set to 'cat | egrep -i 'system user|Exec_Master_Log_Pos|Seconds_Behind_Master|Read_Master_Log_Pos''
mysql> show slave status \G;
Read_Master_Log_Pos: 5370489
Exec_Master_Log_Pos: 5370489
Seconds_Behind_Master: 0
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> nopager; //恢復之前的顯示狀態
PAGER set to stdout
