rm -- --testings.html
The --
option tells rm to treat all further arguments as file names, not as options, even if they start with -
.
This isn’t particular to the rm command. The getopt function implements it, and many (all?) UNIX-style commands treat it the same way: --
terminates option processing, and anything after it is a regular argument.
http://www.gnu.org/software/hello/manual/libc/Using-Getopt.html#Using-Getopt