tar cvf or tar -cvf ?

Question

I have learned to use tar without '-' for options, like tar cvfz dir.tar.gz Directory/ but I recently came accross the slightly different tar -czvf syntax (I think the 'f' must be the last option in this case).

Both work on linux and Mac OS. Is there a recommended syntax, with ou without '-' which is more portable accross unix flavors ?

Answer 1

tar is one of those ancient commands from the days when option syntax hadn't been standardized. Because all useful invocations of tar require specifying an operation before providing any file name, most tar implementations interpret their first argument as an option even if it doesn't begin with a -. Most current implementations accept a -; the only exception that I'm aware of is Minix.

Older versions of POSIX and Single Unix included a tar command with no - before the operation specifier. Single Unix v2 had both traditional archivers cpio and tar, but very few flags could be standardized because existing implementations were too different, so the standards introduced a new command, pax, which is the only standard archiver in since Single Unix v3. If you want standard compliance, use pax, but beware that many Linux distributions don't include it in their base installation, and there's no pax in Minix. If you want portability in practice, use tar cf filename.tar.

Answer 2

I may be a dinosaur, but I think that habitually using "cvf" instead of "-cvf" is probably more portable. I imagine most Linux distros use GNU tar, and I would guess that the *BSDs do also, but you'll find proprietary Unixes that still use the old SysV tar, which used to require you to not use a '-' in the options.

I do not use "-cvf" (or "-xf" or whatever) and I have no trouble even with bleeding edge Arch linux.

And just as a side note, I think you can use the Sun-standard "jar" command options with or without a '-' as well.