mysql not to print selects output to terminal

You can redirect the output of any command -- not just MySQL -- by using your shell's i/o redirection operators. For example, in bash:

$ mysql mydb < commands.sql > /dev/null 2>&1

This will launch the MySQL command line client, connect it to "mydb" on the local system (assuming you have access), read SQL commands from the file commands.sql and dump all the output to /dev/null.

If you wanted to save the output for review after the fact, you could redirect it to a file rather than to /dev/null:

$ mysql mydb < commands.sql > output.txt 2>&1

The 2>&1 redirects stderr as well as stdout. If you wanted to see any errors on your terminal, you would only redirect stdout:

$ mysql mydb < commands.sql > /dev/null

1. mysql-client:

   mysql> pager > /dev/null
   PAGER set to '> /dev/null'
   mysql> select 1;
   1 row in set (0.00 sec)
   
   mysql> \q
   Bye
   

   This way the result of the queries is not printed, only row count an timing information.

2. IO redirection in the shell

   user@host$ mysql -e 'select 1' > /dev/null
   user@host$
   

If the purpose is to warm up the cache, you could also do something like:

select max(concat( col1,col2 ) ) from mytable where ...

The engine is forced to read the real pages to compute the max (with little overhead relative to the I/O anyway)

Note that if you select only columns from an index, only the index is red, there is no need to go to the table itself ("cover index").
In some cases you may want exactly that (load only the index into the cache)