I have thousands of shapefiles that I would like to rename, all are currently named "cYYYDDD_Union_Clip_Clip" and I would like to ultimately rename each to "YYYYDDDD_abc")? I've tried using Iterator in ModelBuilder with in-line variable substitution but as I understand both I can only substitute the existing shapefile name (e.g. the best I can do with Iterator and in-line substitution is maintain the input name as the output name). Any one know what I can do to rename multiple shapefiles in an automated fashion?
@klewis gives a good solution. However, as it is just file name changes based on a pattern you want, even simpler, and almost certainly faster because it by-passes ArcGIS altogether, is to write a script (pick your favourite language) to walk the file directory directly. Just make sure you change all files so you catch all the components of the shapefile e.g. .shp, .shx, .prj and so on, but if you apply your script to all files that should happen automatically anyway.
There are loads of examples of how to do this on the 'net and in other Stackexchange sites (e.g. see here or here etc). There's nothing magical about the shapefile and any of the 'standard' solutions will work so long as all parts of the file share the same name (before the extension). By not invoking your GIS, especially Arc, for this simple operation you avoid a huge overhead. If it had been a Geodatabase... well that would have been a very different matter.
Whatever solution you go for, I recommend making a zip archive of your data first though, in case either your process or choice of name proves unfortunate later.