在mysql日常操作中，妙用pager设置显示方式，可以大大提高工作效率。比如select出来的结果集超过几个屏幕，那么前面的结果一晃而过无法看到，这时候使用pager可以设置调用os的more或者less等显示查询结果，和在os中使用more或者less查看大文件的效果一样。

pager用法：

实际上等于将它设置以后的所有mysql操作命令的输出通过pager设置命令执行，类似于管道符的作用

nopager命令：取消pager设置，恢复之前的输出状态。(如果不设置nopager，那么只能通过重启mysql服务才能恢复了)

举些例子来说明吧：

1)当处理大量数据时，不想显示查询的结果，而只需知道查询花费的时间。

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; //实际上等于后面执行的命令|cat /dev/null，这样显示结果就只是执行时间了

PAGER set to 'cat /dev/null'

mysql> select * from huanqiu.haha;

5 rows in set (0.00 sec)

mysql> nopager; //恢复之前的输出状态

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)如果有大量连接，用show processlist看不方便，想看有多少Sleep状态，则可以用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; //类似于show processlist结果再通过grep Sleep |wc -l显示；下面表示一共有2个连接，其中0个Sleep状态的连接。

0

2 rows in set (0.00 sec)

mysql> nopager; //恢复之前的输出状态

3)设置pager，只查看slave状态的几个status值。

mysql> show slave status \G; //其中的\G表示显示要换行显示

*************************** 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; //恢复之前的显示状态

PAGER set to stdout