启动psql时加上 -E 参数，就可以将 "\" 开头的命令执行的实际SQL打印出来。如：
其实就是 \set ECHO_HIDDEN on 的效果，要关闭这个效果，只需要 \set ECHO_HIDDEN off

[postgres@mutou]$ psql -E
Timing is on.
psql (9.4.1)
Type "help" for help.


[postgres:6446@postgres] [12-25.16:42:09]=# \l
********* QUERY **********
SELECT d.datname as "Name",
       pg_catalog.pg_get_userbyid(d.datdba) as "Owner",
       pg_catalog.pg_encoding_to_char(d.encoding) as "Encoding",
       d.datcollate as "Collate",
       d.datctype as "Ctype",
       pg_catalog.array_to_string(d.datacl, E'\n') AS "Access privileges"
FROM pg_catalog.pg_database d
ORDER BY 1;
**************************


                                 List of databases
   Name    |  Owner   | Encoding |  Collate   |   Ctype    |   Access privileges   
-----------+----------+----------+------------+------------+-----------------------
 postgres  | postgres | UTF8     | en_US.utf8 | en_US.utf8 | 
 repmgr    | repmgr   | UTF8     | en_US.utf8 | en_US.utf8 | 
 template0 | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
           |          |          |            |            | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
           |          |          |            |            | postgres=CTc/postgres
 users     | dbmgr    | UTF8     | en_US.utf8 | en_US.utf8 | 
(6 rows)

[postgres:6446@postgres] [12-25.16:58:31]=# \set ECHO_HIDDEN off  <<<<<<<<< 注意ECHO_HIDDEN需要大写
[postgres:6446@postgres] [12-25.16:58:45]=# \dn
  List of schemas
  Name  |  Owner   
--------+----------
 public | postgres
(1 row)