SQL*Plus commands
The following commands can be issued in SQL*Plus (in addition to the standard SQL commands.)
   @ pathname  Run an SQL Script (see START)
               @MyScript.sql parameter1 parameter2 parameter3 
               In the SQL-Script, refer to the parameters as &1, &2, and &3.
   @@ pathname Run a nested SQL Script.
   /           Execute (or re-execute) commands in the SQL*Plus buffer
               does not list commands before running
   ACCEPT      User input
               ACC[EPT] variable [NUM[BER]|CHAR|DATE] [FORMAT format]
                  [DEFAULT default] [PROMPT text|NOPROMPT] [HIDE]
   APPEND      Add text to the end of the current line in the buffer.
               A[PPEND] text_to_add
   BREAK       Specify where and how formatting will change.
               BREAK ON {column|expr|ROW|REPORT} action
   BTITLE      Place and format a title at the bottom of each page.
               BTITLE printspec [text|variable]
               BTITLE [OFF|ON]
   CHANGE      Change text on the current line.
               C /oldval/newval
   CLEAR       Clear the SQL*Plus screen and the screen buffer.
               CLEAR {BREAKS|BUFFER|COLUMNS|COMPUTES|SCREEN|SQL TIMING}
   COLUMN      Change display width of a column.
   COMPUTE     Calculate and display totals.
   CONNECT     Connect to a database as a specified user.
               connect username/password@SID
   COPY        Copy data from a query into a table (local or remote)
   DEFINE      User variables:
                  DEFINE <varName> = <String>
               Display a user variable
                  DEFINE <varName>
               Display all variables
                  DEFINE
   DEFINE_EDITOR = sql*plus editor (e.g. DEFINE_EDITOR=vim.exe)
   DEL         Delete the current line in the SQL buffer
   DESC[RIBE]  Describe a table, column, view, synonym, function
               procedure, package or package contents.
   DISCONNECT  Logoff (but don't exit)
   EDIT        Load the SQL*Plus buffer into an editor. 
               By default, saves the file to AFIEDT.BUF
   EXECUTE     Run a single PLSQL statement
               EXEC :answer := EMP_PAY.BONUS('SMITH')
   EXIT [n]    Commit, logoff and exit (n = error code)
               EXIT SQL.SQLCODE
   GET file    Retrieve a previously stored command file
   HELP topic  Topic is an SQL PLUS command or HELP COMMANDS
   HOST        Execute a host operating system command
               HOST CD scripts
   INPUT       Edit sql buffer - add line(s) to the buffer
   LIST n m    Edit sql buffer - display buffer lines n to m
               For all lines - specify m as LAST
   PAUSE message   Wait for the user to hit RETURN
   
   PRINT variable  List the value of a bind variable or REF Cursor (see VARIABLE / SHOW)
   PROMPT message  Echo a message to the screen   
   REMARK      REMARK comment or --comment--  or /* comment */
   RUN         Execute (or re-execute) commands in the SQL*Plus buffer
               Lists the commands before running
   RUNFORM     Run a SQL*Forms application
   SAVE file   Save the contents of the SQL*Plus buffer in a command file
               SAVE file [CRE[ATE] | REP[LACE] | APP[END]] 
   SET         Display or change SQL*Plus settings
   SHOW        List the value of a system variable (see PRINT)
   SHUTDOWN [ABORT|IMMEDIATE|NORMAL|TRANSACTIONAL]
   SPOOL file  Store query results in file
   SPOOL OFF   Turn off spooling
               SPOOL OUT sends file to printer
   SQLPLUS     Start SQL*Plus and connect to a database.
   STA[RT]     Run an SQL Script (see @)
   STARTUP [NoMOUNT|MOUNT|OPEN]
   TIMING      Record timing data TIMING {START | SHOW | STOP}
               see CLEAR TIMING
   TTITLE      Define a page title
   UNDEFINE    Delete a user variable or passed parameter (see DEFINE)
   VARIABLE    Define a bind variable
               (Can be used in both SQLPlus and PLSQL)
               VAR[IABLE] [variable {NUMBER|CHAR|CHAR (n)}]
               VARIABLE on its own will display the definitions made.
   WHENEVER OSERROR   Exit if an OS error occurs
   WHENEVER SQLERROR  Exit if an SQL or PLSQL error occurs
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Related:
  
  Technet Article - 
  SQL*Plus Substitution Variables
  Dizwell.com -
Enable SQL*Plus History (Up-arrow)