Certain ex commands you use only within vi, such as maps, abbreviations, and so on. If you store these commands in your .exrc file, the commands will automatically be executed when you invoke vi. Any file that contains commands to execute is called a script.
The commands in a typical .exrc script are of no use outside vi. However, you can save other ex commands in a script, and then execute the script on a file or on multiple files. Mostly you'll use substitute commands in these external scripts.
For a writer, a useful application of ex scripts is to ensure consistency of terminology—or even of spelling—across a document set. For example, let's assume that you've run the UNIX spell command on two files and that the command has printed out the following list of misspellings:
$ spell sect1 sect2 chmod ditroff myfile thier writeable
As is often the case, spell has flagged a few technical terms and special cases it doesn't recognize, but it has also identified two genuine spelling errors.
Because we checked two files at once, we don't know which files the errors occurred in or where they are in the files. Although there are ways to find this out, and the job wouldn't be too hard for only two errors in two files, you can easily imagine how time-consuming the job could grow to be for a poor speller or for a typist proofing many files at once.
To make the job easier, you could write an ex script containing the following commands:
%s/thier/their/g %s/writeable/writable/g ...