writing mysql output to file in CentOS 7

I am trying to run the following command from inside the mysql command line client in the CentOS terminal:

SELECT Concat('TRUNCATE TABLE ',table_schema,'.',TABLE_NAME, ';')  
FROM INFORMATION_SCHEMA.TABLES where  table_schema in ('justatest')  
INTO OUTFILE '/home/user/tmp/truncate.sql';

The result is this error:

ERROR 1 (HY000): Can't create/write to file '/home/user/tmp/truncate.sql' 
(Errcode: 13 - Permission denied)

I then opened a new terminal, typed su -, gave the password, and then typed the following commands:

chown root:root /home/user/tmp
chmod 1777 /home/user/tmp

But I still get the same error when I run the original SQL code at top above.

EDIT:

I also get the same error when I try:

chown username:username /home/user/tmp
chmod 1777 /home/user/tmp

and the same error message when I try:

chown mysql:mysql /home/user/tmp
chmod 1777 /home/user/tmp

How can I resolve this error?