How to Take Backup Database Link In Oracle 10g,11g,12c

For All DB links backup:
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set pages 0
set long 90000
set trimspool on
SELECT u.OWNER,DBMS_METADATA.GET_DDL('DB_LINK',u.DB_LINK,u.OWNER) FROM dba_db_links u;

For All Specific DB link backup:
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set pages 0
set long 90000
set trimspool on
SELECT DBMS_METADATA.GET_DDL('DB_LINK','&DB_LINK_NAME','&USER_NAME') FROM dba_db_links;