使用cat -n 命令可以查看postmaster.pid文件内容：
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根据每一行进行解释，并给出对应的源代码说明 13795: 代表Postgres主进程的PID/usr/local/pgsql/data: 代表数据目录
1529235109： 代表postmaster文件的创建时间。
5432: 代表数据库监听端口，在postgresql.conf中对应port = 5432
来自源代码说明：
/* The socket number we are listening for connections on */intPostPortNumber; 12/tmp: 代表是unix socket的监听目录，在postgresql.conf中对应 unix_socket_directory = '/tmp'来自源代码说明：
/* The directory names for Unix socket(s) */char *Unix_socket_directories; 12*** **: 代表数据库监听地址，对应postgresql.conf的listen_addresses = '* '来自源代码说明：
/* The TCP listen address(es) */char *ListenAddresses; 125432001 163840:代表的是共享内存的地址(shared memory segments中的key和shmid)。输入ipcs可以查看：
注： postmaster.pid显示的是key转成10进制后的数字。
ready 代表主进程状态typedef enum{PM_INIT,/* postmaster starting */PM_STARTUP,/* waiting for startup subprocess */PM_RECOVERY,/* in archive recovery mode */PM_HOT_STANDBY,/* in hot standby mode */PM_RUN,/* normal "database is alive" state */PM_WAIT_BACKUP,/* waiting for online backup mode to end */PM_WAIT_READONLY,/* waiting for read only backends to exit */PM_WAIT_BACKENDS,/* waiting for live backends to exit */PM_SHUTDOWN,/* waiting for checkpointer to do shutdown * ckpt */PM_SHUTDOWN_2,/* waiting for archiver and walsenders to * finish */PM_WAIT_DEAD_END,/* waiting for dead_end children to exit */PM_NO_CHILDREN/* all important children have exited */} PMState;