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set trimout [SQL*Plus]

set trimout on
set trimout off
If trimsout is set to on, it will remove trailing blanks in the output to the console (terminal).
See also trimspool which does the same thing to spooled output.

Storing settings across sessions

Settings (such as sqlpluscompatibility) can be stored accross sessions with the glogin.sql and/or login.sql file.