Simply put, sometimes, there are situations in where you just want to clear the contents of a file without deleting it.

This could be for many reasons like to avoid permission related issues, or maybe the file could be having useless logs that amasses to a size that measures in GBs.

So, the easiest solution is to clear it away from a terminal is by shell redirection like so:

:> filename

Let me break down the command here:

• The : symbol means true and doesn't produce any output.
• The '>' symbol is used for redirecting the output of the preceding command (in this case, it's empty!)
• filename is the file that you want to truncate. If it doesn't exist, the file will be created.

Alternatively, you can do the same by using the cat command to output the contents of the /dev/null device (which only contains a EOL character) to empty a file:

cat /dev/null > filename

Hope this comes in handy!