How to get the mac address of connected client in postgresql log?

Question

Whenever user connects to PostgreSQL database, i want to show the MAC address of that connected user in the log file of PostgreSQL. How to do it?

Answer 1

https://www.postgresql.org/docs/current/static/runtime-config-logging.html#guc-log-line-prefix

%a    Application name    yes
%u    User name   yes
%d    Database name   yes
%r    Remote host name or IP address, and remote port yes
%h    Remote host name or IP address  yes
%p    Process ID  no
%t    Time stamp without milliseconds no
%m    Time stamp with milliseconds    no
%n    Time stamp with milliseconds (as a Unix epoch)  no
%i    Command tag: type of session's current command  yes
%e    SQLSTATE error code no
%c    Session ID: see below   no
%l    Number of the log line for each session or process, starting at 1   no
%s    Process start time stamp    no
%v    Virtual transaction ID (backendID/localXID) no
%x    Transaction ID (0 if none is assigned)  no
%q    Produces no output, but tells non-session processes to stop at this point in the string; ignored by session processes   no
%%    Literal %

you can't.

Of course you can get it form arp cache or other system utility, but not with postgres log_line_prefix