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SQL*Plus: SPOOL

spool sends the output that is normally written to the console also to a file or printer, or (spool off) turns this additional output off.

See also

set termout off prevents printing output to the console, which is especially useful while spooling to a file.
spool.sql and spool_off.sql are two SQL scripts for $SQLPATH that modify SQL*Plus settings in a way that spool creates clean output.
Using spool to write DDL statements created by dbms_metadata.get_ddl to an SQL script file.
SQL*Plus

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