M: Is there a way in Linux, a command line sequence, to replace a given file with an empty, zero bite file with the same name
G: Yes. To replace a file with an empty (zero-byte) file while preserving the filename, use:
: > filename: is a no-op command (does nothing, but exits
successfully).> redirects its (empty) output to
filename, overwriting it with nothing — resulting in a
zero-byte file.truncate -s 0 filenameBoth methods are safe and efficient. Use truncate if you
want clearer intent; use : > for brevity.
M: My intent is to save space when using a download utility; since it automatically updates from a set of online folders, what I want to do is after checking through them, zero out the ones I’ve already retrieved and reviewed so that later checks will see the presence of a fileof the name and skip downloading it. My question is: will using truncate work to save space, or will the original file space still be registered in the file structure as being of the original size, rendering my efforts pointless?
G: Your approach will work as intended if you're using a regular filesystem and not dealing with certain edge cases like sparse files, hard links, or copy-on-write systems.
truncate -s 0 file or : > file
does free the disk space used by that file on most
filesystems (ext4, xfs, etc.).du, ls -lh) will show the
space as freed.After truncating, run:
du -sh filenameIt should show 0 or very low disk usage.
And you can check total space freed via:
df -h .Compare before and after.
This method is often used in space-saving workflows. You're not wasting effort.