Indenting in VIM with all the files in Folder

I have a folder containing hundreds of TTL (TeraTermLanguage) files. Now I wanted indent all these files.

I have created teraterm.vim for indentation and I open a file using VIM and do "gg=G" and whole file gets indented properly.

But is there any way, where I can indent all the files in folder.

I wanted to do with help of Shell. But in VIM I couldnt pass file indent command as the argument to VIM.

Please suggest which is the best way I can do indentation to all the files in VIM.