## Demo of deleting a logfile in use
$ echo "the owls are not what they seem" > filename # Create a file
$ exec 5<filename # Open filename for reading, into FD 5
$ rm filename # delete filename.
$ ls -l filename # The directory entry will be gone -
ls: cannot access filename: No such file or directory
cat <&5 # ...but the file still exists, since we have it open.
the owls are not what they seem
$ exec 5<&- # Only on close will it TRULY be deleted from disk.

## Demo of truncating a file in use
echo "the owls are not what they seem" > filename # Create a file
$ exec 5<filename # Open filename for reading, into FD 5
$ : > filename # truncate filename
$ ls -l filename # The same file exists, with zero size
-rw-r--r-- 1 username users 0 Oct  7 11:40 filename
$ cat <&5 # Read from the file.  Nothing there.
$ exec 5<&- # close the file.

Also, would 

Code:

cat /dev/null > file



 have the same potential problem (sudo/redirect issues aside)?