Sqlplus setting in the screen does not print out output

In some specific cases we want to do some kind of experiment, we need to execute a SQL statement, but we don't want to print out the result of the SQL statement on the screen (too long)
You can use the following methods.
1 Write the statement you want to execute into a SQL script, for example:
[Email protected] scripts]$ more Sqlt.sql
Set term off
Alter session set Sql_trace=true;
SELECT * from V$latch;
Alter session set Sql_trace=false;
2 Note that the beginning of the script is set
Set term off


The explanation for the set command is as follows:

Column
Modify column widths
Column C1 Format A20--Adjust column C1 (character) display maximum width to 20 characters
Column C1 Format 9999999--Adjusts the maximum width of the C1 (NUM type) display to 7 characters
Modify column headings
Column C1 Heading C2--Output C1 column name to C2

Set Colsep '      --delimiter for row header column
Set linesize--Sets the maximum line width   the sqlplus output;
Set pagesize      --The maximum number of rows in the Set page defaults to 24, to avoid paging, set to 0
set serveroutput on|off
Set Echo on --Displays each command in the file and its execution result, default to ON 
Set echo off--does not display the command in the file, only displays its execution result
Set term on --the query results are displayed in the spool file ( SPOOL specifies the output of the file), and in the Sqlplus display
set term off--the query results are displayed only in the spool file (spool specified output file)
Set heading off --Let the title of the result row not display, default to on 
Set heading on  --Let the title of the result row display
Set trimout on-removes trailing spaces for each line of the standard output, by default off 
Set Trimspool on- -Remove the trailing space of the redirect (spool) output per line, default to OFF&NBSP,
Set timing off  -shows the time-consuming of each SQL command, default to OFF 
Set Verify Off   -whether to show statements before and after substitution variables are replaced.
exit            --Exit

Set Feedback
There are three ways: the default is on
Set Feedback on;set Feedback off;set Feedback n
By default, when a SQL is issued, Oracle gives a feedback, such as when creating a table, if successful, the command line returns a similar: Table created feedback, or when performing a PL/SQL success, the command line returns: PL/SQL procedure Successfully completed. When running many statements in a script, feedback is generally set to off.
Set Feedback N: When an SQL statement returns n or more than n rows of records, there will be feedback, for example: Set feedback 5, when the return record equals or more than 5 rows will have a similar 8 rows Selected feedback. If the return row is less than 5, there is no feedback.

Set Define Off
The default "&" in Sql*plus represents an alternative variable, that is, Sql*plus will ask you to enter an alternate value whenever the symbol appears in the command. This means that you cannot enter a string containing the symbol into a database or assign to a variable, such as the string "Sql&plus" system will be understood as a string beginning with "SQL", it will prompt you to enter the value of the alternative variable Plus, if you enter ABC, then the final string into " Sqlabc ".
Set define off this function, "&" as a normal character, as in the above example, the final character is "Sql&plus"

Set define off--turn off substitution variable function
Set define on--Open alternate variable function
Set define $ (not alphanumeric and white space) will override the default variable marker & "$", that is, the original & marker will be inserted as a normal character, and the following character will be the variable, prompting you to enter.

Spool command
Spool filename-Writes the contents of the buffer to the specified file filename
Spool off--Terminate write command

MARKUP
Markup is an environment setting for sql*plus that controls the markup language type of the output. By default, markup defines HTML as a markup language, but the label itself is closed. The set of HTML tags is predefined; You must open the label with the following statement:
SET MARKUP HTML on

Sqlplus setting in the screen does not print out output