sedcommand with the
-ioption lets you delete the contents of a read-only file and lets you delete other protected files. The permissions on a file define what actions can take place to that file, while the permissions on a directory define what actions can be taken to the list of files in that directory. For this reason,
seddoes not let you use
-ion a write-enabled file in a read-only directory, and will break symbolic or hard links when the
-ioption is used on such a file.