# echo "" > access.log OR # echo > access.log
Note: You should keep in mind that an empty string is not the same as null. A string is already an object much as it may be empty while null simply means non-existence of an object.
To send a null output to the file, use the flag
-n which tells echo to not output the trailing newline that leads to the empty line produced in the previous command.
# echo -n "" > access.log