[postgres@centos7g4 ~]$ PGPASSWORD=postgres psql -d "host=10.0.2.6,10.0.2.5,10.0.2.15" -c "SELECT hostname(), clock_timestamp()";
    hostname     |        clock_timestamp
-----------------+-------------------------------
 centos7g1.local | 2019-10-20 14:14:25.699558+03
(1 row)

[postgres@centos7g4 ~]$ PGPASSWORD=postgres psql -d "host=10.0.2.6,10.0.2.5,10.0.2.15" -c "SELECT hostname(), clock_timestamp()";
    hostname     |        clock_timestamp
-----------------+-------------------------------
 centos7g1.local | 2019-10-20 14:14:27.599655+03
(1 row)

[postgres@centos7g4 ~]$ PGPASSWORD=postgres psql -d "host=10.0.2.6,10.0.2.5,10.0.2.15" -c "SELECT hostname(), clock_timestamp()";
    hostname     |        clock_timestamp
-----------------+-------------------------------
 centos7g1.local | 2019-10-20 14:14:28.693661+03
(1 row)

[postgres@centos7g4 ~]$ PGPASSWORD=postgres psql -d "host=10.0.2.6,10.0.2.5,10.0.2.15" -c "SELECT hostname(), clock_timestamp()";


[postgres@centos7g4 ~]$ PGPASSWORD=postgres psql -d "host=10.0.2.6,10.0.2.5,10.0.2.15" -c "SELECT hostname(), clock_timestamp()";
    hostname     |        clock_timestamp
-----------------+-------------------------------
 centos7g2.local | 2019-10-20 14:15:55.158207+03
(1 row)

[postgres@centos7g4 ~]$ PGPASSWORD=postgres psql -d "host=10.0.2.6,10.0.2.5,10.0.2.15" -c "SELECT hostname(), clock_timestamp()";
    hostname     |        clock_timestamp
-----------------+-------------------------------
 centos7g2.local | 2019-10-20 14:16:01.740922+03
(1 row)