Change -- to . for all files in a directory

I need to rename all the files in a directory. Some examples of the source filenames are:

alpha--sometext.381928
comp--moretext.7294058

The resultant files would be renamed as:

alpha.sometext.381928
comp.moretext.7294058

The number of cha开发者_高级运维racters before and after the -- is not consistant.

The script needs to work on current installations of Ubuntu and FreeBSD. These are lean LAMP servers so only the necessary packages have been installed.

Thanks

---

As an alternative to pure shell, you can use rename, a standard utility that comes with Perl. It's more convenient for simple cases.

rename 's/--/./' *

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Via bash:

for file in *--*; do
    mv "${file}" "${file/--/.}"
done

The magic is in ${file/--/.} which is the value of ${file} except with each "--" changed to a "."